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TCID	Name	Domain	Kingdom/Phylum	Protein(s)
1.A.1.1.1	Two TMS K⁺ and water channel (conducts K⁺ (K_D = 8 mM); blocked by Na⁺ (190 mM) (Renart et al., 2006) and tetrabutylammonium (Iwamoto et al., 2006)). Ion permeation occurs by ion-ion contacts in single file fashion through the selectivity filter (Köpfer et al. 2014). A narrow pore lined with four arrays of carbonyl groups is responsible for ion selectivity, whereas a conformational change of the four inner transmembrane helices (TMS2) is involved in gating (Baker et al. 2007). Two gates have been identified; one is located at the inner bundle crossing and is activated by H⁺ while the second gate is in the selectivity filter (Rauh et al. 2017). The C-terminal domain mediates pH modulation (Hirano et al., 2011; Pau et al., 2007). KcsA exhibits a global twisting motion upon gating (Shimizu et al., 2008). Activity is influenced by the phase of the lipid bilayer (Seeger et al. 2010), and occupancy of nonannular lipid binding sites increases the stability of the tetrameric complex (Triano et al. 2010). The open conformation of KcsA can disturb the bilayer integrity and catalyze the flipping of phospholipids (Nakao et al. 2014). This protein is identical to the KcsA orthologue (P0A333) in Streptomyces coelicolor. The stability of the pre domain in KcsA is stabilized by GCN4 (Yuchi et al. 2008). The potential role of pore hydration in channel gating has been evaluated (Blasic et al. 2015). Having multiple K⁺ ions bound simultaneously is required for selective K⁺ conduction, and a reduction in the number of bound K⁺ ions destroys the multi-ion selectivity mechanism utilized by K⁺ channels (Medovoy et al. 2016). The channel accomodates K⁺ and H₂O molecules alternately in a K⁺-H₂O-K⁺-H₂O series through the channel (Kratochvil et al. 2016). Insertion of KcsA is spontaneous and directional as the cytosolic part of the protein does not translocate across the membrane barrier. Charged residues, not hydrophobic residues, are crucial for insertion of the unfolded protein into the membrane via electrostatic interactions between membrane and protein. A two-step mechanism was proposed. An initial electrostatic attraction between membrane and protein represents the first step prior to insertion of hydrophobic residues into the hydrocarbon core of the membrane (Altrichter et al. 2016). Bend, splay, and twist distinguish KcsA gate opening, filter opening, and filter-gate coupling, respectively (Mitchell and Leibler 2017). Details of the water permeability have been presented. Water flow through KcsA is halved by 200 mM K⁺ in the aqueous solution, which indicates an effective K⁺ dissociation constant in that range for a singly occupied channel. (Hoomann et al. 2013). A parameterized MARTINI program can be used to predict the hinging motions of the protein (Li et al. 2019). Activation of KcsA is initiated by proton binding to the pH gate upon an intracellular drop in pH which prompts a conformational switch, leading to a loss of affinity for potassium ions at the selectivity filter and therefore to channel inactivation (Rivera-Torres et al. 2016). An alteration in the conformational equilibrium of the intracellular K⁺-gate is one of the fundamental mechanisms underlying the dysfunctions of K⁺ channels caused by disease-related mutations (Iwahashi et al. 2020). Folding and misfolding of KcsA monomers during assembly and tetramerization has been examined (Song et al. 2021). The flexible C-terminus stabilizes KcsA tetramers at a neutral pH with decreased stabilization at acidic pH (Howarth and McDermott 2022). Under equilibrium conditions, in the absence of a transmembrane voltage, both water and K⁺ occupy the selectivity filter of the KcsA channel in the closed conductive state (Ryan et al. 2023).	Bacteria	Actinomycetota	Skc1 (KcsA) of Streptomyces lividans
1.A.1.2.1	Voltage-sensitive K⁺ channel (P_Na⁺/P_K⁺ ≈ 0.1) Shaker and Shab K⁺ channels are blocked by quinidine (Gomez-Lagunas, 2010).	Eukaryota	Metazoa, Arthropoda	Shab11 of Drosophila melanogaster
1.A.1.2.2	Voltage-sensitive K⁺ channel of 498 aas and 6 TMSs, SHAW2. Modulation of the Drosophila Shaw2 Kv channel by 1-alkanols and inhaled anesthetics correlates with the involvement of the S4-S5 linker and C-terminus of S6, consistent with stabilization of the channel's closed state (Zhang et al. 2013).	Eukaryota	Metazoa, Arthropoda	Shaw2 of Drosophila melanogaster
1.A.1.2.3	Voltage-sensitive fast transient outward current K⁺ channel in neurons and muscle of flies and worms (Fawcett et al., 2006)	Eukaryota	Metazoa, Arthropoda	Shal2 of Drosophila melanogaster
1.A.1.2.4	Margatoxin-sensitive voltage-gated K⁺ channel, Kv1.3 (in plasma and mitochondrial membranes of T lymphocytes) (Szabò et al., 2005). K_v1.3 associates with the sequence similar (>80%) K_v1.5 protein in macrophage forming heteromers that like K_v1.3 homomers are r-margatoxin sensitive (Vicente et al., 2006). However, the heteromers have different biophysical and pharmacological properties. The K_v1.3 mitochondrial potassium channel is involved in apoptotic signalling in lymphocytes (Gulbins et al., 2010). Interactions between the C-terminus of K_v1.5 and K_vβ regulate pyridine nucleotide-dependent changes in channel gating (Tipparaju et al., 2012). Intracellular trafficking of the K_V1.3 K⁺channel is regulated by the pro-domain of a matrix metalloprotease (Nguyen et al. 2013). Direct binding of caveolin regulates K_v1 channels and allows association with lipid rafts (Pérez-Verdaguer et al. 2016). Addtionally, Na_vBeta1 interacts with the voltage sensing domain (VSD) of K_v1.3 through W172 in the transmembrane segment to modify the gating process (Kubota et al. 2017). During insertion of Kv1.3, the extended N-terminus of the second α-helix, S2, inside the ribosomal tunnel is converted into a helix in a transition that depends on the nascent peptide sequence at specific tunnel locations (Tu and Deutsch 2017). The microRNA, mmumiR449a, reduced the mRNA expression levels of transient receptor potential cation channel subfamily A member 1 (TRPA1), and calcium activated potassium channel subunit alpha1 (KCNMA1) and increased the level of transmembrane phosphatase with tension homology (TPTE) in the DRG cells (Lu et al. 2017). This channel is regulation by sterols (Balajthy et al. 2017). Loss of function causes atrial fibrillation, a rhythm disorder characterized by chaotic electrical activity of cardiac atria (Olson et al. 2006). The N-terminus and S1 of Kv1.5 can attract and coassemble with the rest of the channel (i.e. Frag(304-613)) to form a functional channel independently of the S1-S2 linkage (Lamothe et al. 2018). This channel may be present in mitochondria (Parrasia et al. 2019). Kv1.3 plays an essential role in the immune response mediated by leukocytes and is functional at both the plasma membrane and the inner mitochondrial membrane. Plasma membrane Kv1.3 mediates cellular activation and proliferation, whereas mitochondrial Kv1.3 participates in cell survival and apoptosis (Capera et al. 2022). Kv1.3 uses the TIM23 complex to translocate to the inner mitochondrial membrane. This mechanism is unconventional because the channel is a multimembrane spanning protein without a defined N-terminal presequence. Transmembrane domains cooperatively mediate Kv1.3 mitochondrial targeting involving the cytosolic HSP70/HSP90 chaperone complex as a key regulator of the process (Capera et al. 2022).	Eukaryota	Metazoa, Chordata	Kv1.3 homomers and Kv1.3/Kv1.5 heteromers of Homo sapiens (P22001) Kv1.3 (P22001) Kv1.5 (P19024)
1.A.1.2.5	Voltage-gated K⁺ channel subfamily D, member 2, Kv4.2 or KCND2, in neurons and muscle; forms complexes with auxiliary subunits and scaffolding proteins via its N-terminus, influencing trafficking, temperature-sensitivity and gating (Radicke et al. 2013).These subunits are (1) dipeptidyl-peptidase-like type II transmembrane proteins typified by DPPX-S (e.g., protein 6, P42658; 865 aas, TC#8.A.51), and (2) cytoplasmic Ca²⁺ binding proteins known as K⁺ channel interacting proteins (KChIPs; TC#8.A.82.2.2; Q6PIL6) (Seikel and Trimmer 2009). The C-terminus interacts with KChIP2 to influence gating, surface trafficking and gene expression (Han et al., 2006; Schwenk et al., 2008). KChIPs (250 aas for mouse KChIP4a; Q6PHZ8) are homologous to domains in NADPH oxidases (5.B.1). Heteropoda toxin 2 (P58426; PDB 1EMX; TC#8.B.5.2.2) interactions with Kv4.3 and Kv4.1 give rise to differences in gating modifications (DeSimone et al., 2011). Mutations cause autism and seizures due to a slowing of channel inactivation (Lee et al. 2014). The stoichiometry of Kv4.2 and DPP6 is 4:4 (Soh and Goldstein 2008). Neferine, an isoquinoline alkaloid from plants, inhibits Kv4.3 channels, probably by blocking the open state (Wang et al. 2015). SUMOylating (derivatizing with a small ubiquitin-like modifier) at two distinct sites on Kv4.2 increases surface expression and decreases current amplitude (Welch et al. 2019). Modulation of voltage-gated potassium (Kv) channels by auxiliary subunits is central to the physiological function of channels in the brain and heart. Native Kv4 tetrameric channels form macromolecular ternary complexes with two auxiliary beta-subunits-intracellular Kv channel-interacting proteins (KChIPs) and transmembrane dipeptidyl peptidase-related proteins (DPPs)-to evoke rapidly activating and inactivating A-type currents, which prevent the backpropagation of action potentials (see above). Kise et al. 2021 investigated the modulatory mechanisms of Kv4 channel complexes, reporting cryo-EM structures of the Kv4.2-DPP6S-KChIP1 dodecameric complex, the Kv4.2-KChIP1 and Kv4.2-DPP6S octameric complexes, and Kv4.2 alone. The structure of the Kv4.2-KChIP1 complex revealed that the intracellular N terminus of Kv4.2 interacts with its C-terminus that extends from the S6 gating helix of the neighbouring Kv4.2 subunit. KChIP1 captures both the N and the C terminus of Kv4.2. Thus, KChIP1 prevents N-type inactivation and stabilizes the S6 conformation to modulate gating of the S6 helices within the tetramer. Unlike the reported auxiliary subunits of voltage-gated channel complexes, DPP6S interacts with the S1 and S2 helices of the Kv4.2 voltage-sensing domain, which suggests that DPP6S stabilizes the conformation of the S1-S2 helices. DPP6S may therefore accelerate the voltage-dependent movement of the S4 helices. KChIP1 and DPP6S do not directly interact with each other in the Kv4.2-KChIP1-DPP6S ternary complex. Thus, two distinct modes of modulation contribute in an additive manner to evoke A-type currents from the native Kv4 macromolecular complex (Kise et al. 2021).	Eukaryota	Metazoa, Chordata	Kv4.2 of Homo sapiens (Q9NZV8)
1.A.1.2.6	Voltage-gated K⁺ channel, Shaker. Shaker and Shab K⁺ channels are blocked by quinidine (Gomez-Lagunas, 2010). Also regulated by unsaturated fatty acids (Börjesson and Elinder, 2011). TMSs 3 and 4 comprise the voltage sensor paddle (Xu et al. 2013). Partially responsible for action potential repolarization during synaptic transmission (Ford and Davis 2014). Shaker K⁺ channels can be mutated in S4 to create an analogous "omega" pore (Held et al. 2018). The NMR structure of the isolated Shaker voltage-sensing domain in LPPG micelles has been reported (Chen et al. 2019). Substituting the first S4 arginine with a smaller amino acid opens a high-conductance pathway for solution cations in the Shaker K⁺ channel at rest. The cationic current does not flow through the central K⁺ pore and is influenced by mutation of a conserved residue in S2, suggesting that it flows through a protein pathway within the voltage-sensing domain (Tombola et al. 2005). The current can be carried by guanidinium ions, suggesting that this is the pathway for transmembrane arginine permeation. Tombola et al. 2005 proposed that when S4 moves, it ratchets between conformations in which one arginine after another occupies and occludes to ions in the narrowest part of this pathway. Specific resin acids activate and open voltage-gated channels dependent on its exact binding dynamics (Silverå Ejneby et al. 2021). Charge-voltage curves of a Shaker potassium channel are not hysteretic at steady state (Cowgill and Chanda 2023). shaker is a critical sleep regulator in Drosophila (Cirelli et al. 2005).	Eukaryota	Metazoa, Arthropoda	Shaker of Drosophila melanogaster (CAA29917)
1.A.1.2.7	Electrically silent lens epithelium K⁺ channel (Delayed rectifier K⁺ channel α-subunit, Kv9.1 (Shepard & Rae, 1999))	Eukaryota	Metazoa, Chordata	Kv9.1 of Homo sapiens (Q96KK3)
1.A.1.2.8	Voltage gated K⁺ channel/MiNK related peptide (MiRP) complex, KVS1(α)/MPS-1/MiRPβ (expressed in chemo- and mechano-sensory neurons. Involved in chemotaxis, mechanotransduction and locomotion (Bianchi et al., 2003)). KVS-1 and KVS-2 are homologous; MPS-1 is member of the MiNK family (8.A.10). KVS-1/MPS-1 association involves hydrophobic forces (Wang and Sesti, 2007).	Eukaryota	Metazoa, Nematoda	KVS-1 (α)/ MPS-1 (MiRPβ) of Caenorhabditis elegans KVS-1 (α) (Q86GI9) MPS-1 (MiRPβ) (Q86GJ0)
1.A.1.2.9	Brain-specific regulatory α-chain homologue that coassembles with other α-subunits to form active heteromultimeric K⁺ channels of unique kinetic properties, Kv2.3r. The functional expression of this regulatory α-subunit represents a novel mechanism without precedents in voltage-gated channels, which contributes to the functional diversity of K⁺ channels (Castellano et al., 1997). Beta subunits regulate the response of human Kv4.3 to protein kinae C phosphorylation and provide a potential mechanism for modifying the response of ion conductance to alpha-adrenergic regulation in vivo (Abbott 2017).	Eukaryota	Metazoa, Chordata	Kv2.3r of Rattus norvegicus (P97557)
1.A.1.2.10	Voltage-gated K⁺ channel, chain A, Shaker-related, K_v1.2 or KCNA2 (Crystal structure known, Long et al., 2007; Chen et al. 2010). It functions with the auxiliary subunit, Ivβ1.2; 8.A.5.1.1) (Peters et al. 2009). Delemotte et al. (2010) described the effects of sensor domain mutations on molecular dynamics of K_v1.2. The Sigma 1 receptor (Q99720; Sigma non-opioid intracellular receptor 1) interacts with K_v1.2 to shape neuronal and behavioral responses to cocaine (Kourrich et al. 2013). Amino acid substitutions cause Shaker to become heat-sensing (opens with increasing temperature as for TrpV1) or cold-sensing (opens with decreasing temperature as for TrpM8) (Chowdhury et al. 2014). The Shaker Kv channel was truncated after the 4th transmembrane helix S4 (Shaker-iVSD) which showed altered gating kinetics and formed a cation-selective ion channel with a strong preference for protons (Zhao and Blunck 2016). Direct axon-to-myelin linkage by abundant K_V1/Cx29 (TC# 1.A.24.1.12) channel interactions in rodent axons supports the idea of an electrically active role for myelin in increasing both the saltatory conduction velocity and the maximal propagation frequency in mammalian myelinated axons (Rash et al. 2016). A cryoEM structure (3 - 4 Å resolution; paddle chimeric channel; closed form) in nanodiscs has been determined (Matthies et al. 2018). Possible gating mechanisms have been discussed (Kariev and Green 2018; Infield et al. 2018). Pathogenic variants in KCNA2, encoding the voltage-gated potassium channel Kv1.2, have been identified as the cause for an evolving spectrum of neurological disorders. Affected individuals show early-onset developmental and epileptic encephalopathy, intellectual disability, and movement disorders resulting from cerebellar dysfunction (Döring et al. 2021). In addition, individuals with a milder course of epilepsy, complicated hereditary spastic paraplegia, and episodic ataxia have been reported. Biophysical properties of a delayed rectifier K⁺ current can contribute to its role ingenerating spontaneous myogenic activity (Hu et al. 2021). The local curvature of cellular membranes acts as a driving force for the targeting of membrane-associated proteins to specific membrane domains, as well as a sorting mechanism for transmembrane proteins, as demonstrated for the chimeric channel, Kv1.2/2.1; KvChim induces a strong positive membrane curvature (Kluge et al. 2022). 2-Aminoethoxydiphenyl borate (2-APB) has inhibitory effects on three K_V1 channels, Kv1.2, Kv1.3 and Kv1.4 (Zhao et al. 2023). Voltage-gated K⁺ channels have two distinct gates that regulate ion flux: the activation gate (A-gate) formed by the bundle crossing of the S6 transmembrane helices and the slow inactivation gate in the selectivity filter. These two gates are bidirectionally coupled. Szanto et al. 2023 suggested that the coupling between the A-gate and the slow inactivation gate is mediated by rearrangements in the S6 segment. S6 rearrangements are consistent with a rigid rod-like rotation of S6 around its longitudinal axis upon inactivation.	Eukaryota	Metazoa, Chordata	K_v1.2 of Homo sapiens (P16389)
1.A.1.2.11	Voltage-gated K⁺ channel, Shab-related, K_v2.1 or KCNB1 (858aas) The crystal structure is known (Long et al., 2007). Rat K_v2.1 and K_v2.2 (long) are colocalized in the somata and proximal dendrites of cortical pyramidal neurons and are capable of forming functional heteromeric delayed rectifier channels. The delayed rectifer currents, which regulate action potential firing, are encoded by heteromeric K_v2 channels in cortical neurons (Kihira et al., 2010). Phosphorylation by AMP-activated protein kinase regulates membrane excitability (Ikematsu et al., 2011). Functional interactions between residues in the S1, S4, and S5 domains of Kv2.1 have been identified (Bocksteins et al., 2011). Missense variants in the ion channel domain and loss-of-function variants in this domain and the C-terminus cause neurodevelopmental disorders, sometimes with seizures (de Kovel et al. 2017). Kv2.1 channels consist of two types of alpha-subunits: (1) electrically-active Kcnb1 alpha-subunits and (2) silent or modulatory alpha-subunits plus beta-subunits that, similar to silent alpha-subunits, regulate electrically-active subunits (Jędrychowska and Korzh 2019). It plays a role in neurodevelopmental disorders, such as epileptic encephalopathy. The N- and C-terminal domains of the alpha-subunits interact to form the cytoplasmic subunit of hetero-tetrameric potassium channels. Kcnb1-containing channels are involved in brain development and reproduction. Modification of Kv2.1 K⁺ currents is mediated by the silent Kv10 subunits (Vega-Saenz de Miera 2004). The clinical expression of KCNB1 encephalopathy is variable (Púa-Torrejón et al. 2021). Variants of KCNB1, located in the S1 segment, may be associated with a milder outcome of seizures (Hiraide et al. 2022). Altered neurological and neurobehavioral phenotypes have been observed in a mouse model of the recurrent KCNB1 -p.R306C voltage-sensor variant (Kang et al. 2023). A point mutation (M340I) in K_V2.1 may cause severe and treatment-resistant obsessive-compulsive disorder (trOCD) (Chen et al. 2023; Ji et al. 2023). It may play a role in Parkinson's Disease (Zhou et al. 2023). An autism-associated KCNB1 mutation dramatically slows Kv2.1 potassium channel activation, deactivation and inactivation (Manville RW et al., 2024 [not yet in PubMed]).	Eukaryota	Metazoa, Chordata	K_v2.1/K_v2.2 of Homo sapiens (Q14721) (Q92953)
1.A.1.2.12	Voltage-gated K⁺ channel, Kv1.1 or KCNA1. It is palmitoylated, modulating voltage sensing (Gubitosi-Klug et al. 2005). It is regulated by syntaxin (TC family 8.A.91) through dual action on channel surface expression and conductance (Feinshreiber et al., 2009). Defects cause episodic ataxia type 1 (EA1), an autosomal dominant K⁺ channelopathy accompanied by short attacks of cerebellar ataxia and dysarthria (D'Adamo et al. 2014; Yuan et al. 2020). Direct axon-to-myelin linkage by abundant K_V1/Cx29 channel interactions in rodent axons supports the idea of an electrically active role for myelin in increasing both the saltatory conduction velocity and the maximal propagation frequency in mammalian myelinated axons (Rash et al. 2016). Kv1.1 is present in bull sperm where it is necessary for normal sperm progressive motility, percent capacitated spermatozoa (B-pattern) and the acrosome reaction (Gupta et al. 2018). Gating induces large aqueous volumetric remodeling (Díaz-Franulic et al. 2018). Paulhus et al. 2020 have reviewed the pathology of mutants in this protein and showed that epilepsy or seizure-related variants tend to cluster in the S1/S2 transmembrane domains and in the pore region of Kv1.1, whereas EA1-associated variants occur along the whole length of the protein, but variants at the C-terminus are more likely to suffer from seizures and neurodevelopmental disorders (Yuan et al. 2020). Mutation in KCNA1 has been identified that impairs voltage sensitivity (Imbrici et al. 2021). Altering expression of the genes encoding Kv1.1, Piezo2, and TRPA1 regulate the response of mechanosensitive muscle nociceptors (Nagaraja et al. 2021). Genetic variants have expanded the functional, molecular, and pathological diversity of KCNA1 channelopathies (Paulhus and Glasscock 2023). Carbamazepine suppresses the impaired startle response and brain hyperexcitability in kcna1a(-/-) zebrafish but had no effect on the seizure frequency in Kcna1(-/-) mice, suggesting that this EA1 zebrafish model might better translate to humans than rodents (Dogra et al. 2023). A lthough they are present at low levels and only generate small currents in the sinoatrial node, Kv1.1 channels have a significant impact on cardiac pacemaking (Short 2024). Episodic ataxia 1 (EA1) is caused by mutations in KCNA1 encoding a neuronal voltage-gated potassium channel (Graves et al. 2024).	Eukaryota	Metazoa, Chordata	Kv1.1 of Homo sapiens (Q09470)
1.A.1.2.13	Voltage-gated K⁺channel subfamily C member 3,KCNC3 or Kv3.3. It is negatively modulated by protein kinase C (Desai et al., 2008). Phosphorylation of Kv3.3 by PKC may allow neurons to maintain action potential height during stimulation at high frequencies, and therefore contributes to stimulus-induced changes in the intrinsic excitability of neurons such as those of the auditory brainstem (Desai et al., 2008). N-glycosylation impacts the sub-plasma membrane localization and activity of Kv3.1b-containing channels, and N-glycosylation processing of Kv3.1b-containing channels contributes to neuronal excitability (Hall et al. 2017). Spinocerebellar ataxia (SCA), a genetically heterogeneous disease characterized by cerebellar ataxia, involves the abnormal expansion of repeat sequences as well as the mutation of K⁺ and Ca²⁺ channel genes (Tada et al. 2020). A missense mutation in Kcnc3 causes hippocampal learning deficits in mice (Xu et al. 2022).	Eukaryota	Metazoa, Chordata	Kv3.3 of Homo sapiens (Q14003)
1.A.1.2.14	Voltage-gated delayed rectifier K⁺ channel, Kv1 of the octopus. RNA editing underlies adaption (Garrett and Rosenthal, 2012). 94% identical to the squid giant axon delayed rectifier voltage-dependent potassium channel, SqKv1A (Q25376).	Eukaryota	Metazoa, Mollusca	Kv1 of Octopus vulgaris (H2EZS9)
1.A.1.2.15	Potassium voltage-gated channel subfamily S member 3 (Delayed-rectifier K(+) channel alpha subunit 3) (Voltage-gated potassium channel subunit Kv9.3)	Eukaryota	Metazoa, Chordata	KCNS3 of Homo sapiens
1.A.1.2.16	Potassium voltage-gated channel subfamily S member 2 (Delayed-rectifier K(+) channel alpha subunit 2) (Voltage-gated potassium channel subunit Kv9.2)	Eukaryota	Metazoa, Chordata	KCNS2 of Homo sapiens
1.A.1.2.17	Potassium voltage-gated channel (KCNH) subfamily G member 3 (Voltage-gated potassium channel subunit Kv10.1) (Voltage-gated potassium channel subunit Kv6.3). Splice variants have different properties and can activate cyclin-dependent protein kinases (Ramos Gomes et al. 2015). Control of transport (pore) function by the voltage sensor may involve more than one mechanism (Tomczak et al. 2017). The silent (non transporting) behaviour of Kv6.3 in the ER is caused by the C-terminal part of its sixth transmembrane domain that causes ER retention (Ottschytsch et al. 2005). De novo missense variants in KCNH1 encoding Kv10.1 are responsible for two clinically recognisable phenotypes: Temple-Baraitser syndrome (TBS) and Zimmermann-Laband syndrome (ZLS) (Aubert Mucca et al. 2022). The clinical overlap between these two syndromes suggests that they belong to a spectrum of KCNH1-related encephalopathies. Affected patients have severe intellectual disability (ID) with or without epilepsy, hypertrichosis and distinctive features such as gingival hyperplasia and nail hypoplasia/aplasia (Aubert Mucca et al. 2022).	Eukaryota	Metazoa, Chordata	Kcng3 or K_v10.1of Rattus norvegicus
1.A.1.2.18	Potassium voltage-gated channel subfamily F member 1 (Voltage-gated potassium channel subunit Kv5.1) (kH1)	Eukaryota	Metazoa, Chordata	KCNF1 of Homo sapiens
1.A.1.2.19	The voltage-gated K⁺ channel subfamily D member 3, KCND3 or K_v4.3. Mutations cause spinocerebellar ataxia type 19 (Duarri et al. 2012). Positively charged residues in S4 contribute to channel inactivation and recovery (Skerritt and Campbell 2007). The crystal structure of Kv4.3 with its regulatory subunit, Kchip1, has been solved (2NZ0) (Wang et al. 2007).	Eukaryota	Metazoa, Chordata	KCND3 of Homo sapiens
1.A.1.2.20	Shaker K⁺ channel, Shk-1, Shk1, Kv1 of 536 aas and 6 TMSs. Mediates the voltage-dependent potassium ion permeability of excitable membranes. It plays a role in repolarization and in regulating the pattern of action potential firing. Isoform a expresses currents in a more depolarized voltage range than isoform d (Liu et al. 2011).	Eukaryota	Metazoa, Nematoda	Shk-1 of Caenorhabditis elegans
1.A.1.2.21	Shal (SHL-1, Kv4) K⁺ channels of 578 aas and 6 TMSs are the predominant transient outward current in C. elegans muscle. SHL-1 expression occurs in a subset of neurons, body wall muscle and in male-specific diagonal muscles (Fawcett et al. 2006) and control the excitability of neurons and cardiac myocytes by conducting rapidly activating-inactivating currents. Activity is modulated by three K⁺ channel interacting (KChIP) soluble auxiliary subunits, NCS-4, NCS-5, and NCS-7. All three ceKChIPs alter electrical characteristics of SHL-1 currents by slowing down inactivation kinetics and shifting voltage dependence of activation to more hyperpolarizing potentials. Native SHL-1 current is completely abolished in cultured myocytes of Triple KO worms in which all three KChIP genes are deleted (Chen et al. 2015).	Eukaryota	Metazoa, Nematoda	Shal of Caenorhabditis elegans
1.A.1.2.22	K⁺ channel, jShak1 of 487 aas and 6 TMSs. Intramolecular interactions control voltage sensitivity (Sharmin and Gallin 2016).	Eukaryota	Metazoa, Cnidaria	jShak1 of Polyorchis penicillatus (Hydromedusa; jellyfish)
1.A.1.2.23	Voltage-gated potassium channel subunit Kv8.2, KCNC2, of 545 aas and 6 TMSs. Mutation causes central ellipsoid loss which involves cone dystrophy with supernormal rod electroretinogram. It is a monogenic disease due to KCNV2 gene mutations that affect KCNC2 channel function in rod and cone photoreceptors (Xu et al. 2017).	Eukaryota	Metazoa, Chordata	KCNC2 of Homo sapiens
1.A.1.2.24	Voltage-gated K⁺ channel, KCNC1 (K_v3.1) of 511 aas and 6 TMSs. It plays an important role in the rapid repolarization of fast-firing brain neurons. The channel opens in response to the voltage difference across the membrane, forming a potassium-selective channel through which potassium ions pass in accordance with their electrochemical gradient (Muona et al. 2015). Can form functional homotetrameric channels and heterotetrameric channels that contain variable proportions of KCNC2 (TC# 1.A.1.2.23), and possibly other family members as well. Contributes to fire sustained trains of very brief action potentials at high frequency in pallidal neurons. Causes various genetic neurological disorders when functioning abnormally such as attention deficit/hyperactivity (Yuan et al. 2017), myoclonus epilepsy and ataxia (Oliver et al. 2017) and intellectual disability (Poirier et al. 2017). The lipid environment, including 7-ketocholesterol (7KC), 24S-hydroxycholesterol (24S-OHC) and tetracosanoic acid (C24:0) affects Kv3.1b channel expression/functionality (Bezine et al. 2018).	Eukaryota	Metazoa, Chordata	KCNC1 of Homo sapiens
1.A.1.2.25	Potassium voltage-gated channel subfamily B member 2, K_v2.2 or KCNB2 of 911 aas and 6 TMSs. Selective expression of HERG (TC# 1.A.1.20.1) and Kv2 channels influences proliferation of uterine cancer cells (Suzuki and Takimoto 2004).	Eukaryota	Metazoa, Chordata	Kv2.2 of Homo sapiens
1.A.1.2.26	Potassium voltage-gated channel subfamily G member 4, KCNG4, of 519 aas and 6 TMSs. Potassium channel subunit that does not form functional channels by itself, but can form functional heterotetrameric channels with KCNB1; modulates the delayed rectifier voltage-gated potassium channel activation and deactivation rates of KCNB1 (Mederos Y Schnitzler et al. 2009).	Eukaryota	Metazoa, Chordata	KCNG4 of Homo sapiens
1.A.1.2.27	Potassium voltage-gated channel subfamily G member 1, KCNG1, of 513 aas and 6 TMSs. Expressed in brain and placenta, and at much lower levels in kidney and pancreas (Su et al. 1997). This potassium channel subunit does not form functional channels by itself, but can form functional heterotetrameric channels with KCNB1. It modulates the delayed rectifier voltage-gated potassium channel activation and deactivation rates of KCNB1 (Mederos Y Schnitzler et al. 2009). KCNG1 mutations cause a syndromic form of congenital neuromuscular channelopathy (Jacinto et al. 2021).	Eukaryota	Metazoa, Chordata	KCNG1 of Homo sapiens
1.A.1.2.28	Potassium voltage-gated channel subfamily D member 1, K_v4.1 of 647 aas and 6 TMSs. It is the pore-forming α-subunit of a voltage-gated rapidly inactivating A-type potassium channel. It may contribute to I(To) current in the heart and I(Sa) current in neurons. Channel properties are modulated by interactions with other α-subunits and with regulatory subunits, KChIP-1 and DPPX-S. The complex voltage-dependent gating rearrangements are not limited to the membrane-spanning core but include the intracellular T1-T1 tetramerization domains interface (Wang and Covarrubias 2006). Artemisinin has an antiarrhythmic effect on wedge preparation models of Brugada syndrome (BrS). It may work by inhibiting potassium channels including I(to) channels, subsequently suppressing ventricular tachycardia/ventricular fibrillation (Jeong et al. 2023). The Kv4 potassium channel modulator NS5806 attenuates cardiac hypertrophy (Cai et al. 2024).	Eukaryota	Metazoa, Chordata	Kv4.1 of Homo sapiens
1.A.1.2.29	K⁺ channel of 529 aas and 6 TMSs, Kv1.6 or KCNA6. It can form functional homotetrameric channels and heterotetrameric channels that contain variable proportions of KCNA1, KCNA2, KCNA4, KCNA6, and possibly other family members (). channel properties depend on the type of alpha subunits that are part of the channel. Channel properties are modulated by cytoplasmic beta subunits that regulate the subcellular location of the alpha subunits and promote rapid inactivation (By similarity). Homotetrameric channels display rapid activation and slow inactivation (Grupe et al. 1990). It is inhibited by 0.6 μM β-defensin 3 (BD3) (Zhang et al. 2018) as well as by neurotoxic cone snail peptide μ-GIIIA and other conotoxins (Leipold et al. 2017).	Eukaryota	Metazoa, Chordata	Kv1.6 of Homo sapiens
1.A.1.2.30	Potassium channel protein of 542 aas and 10 TMSs in a 2 + 2 + 6 TMS toplogy, where the last 6 TMSs comprise the voltage-gated K⁺ channel.	Bacteria	Mycoplasmatota	K⁺ channel of Haloplasma contractile
1.A.1.2.31	The KCNA4 OR K_v1.4 K⁺ channel of 653 aas and 6 TMSs (potassium voltage-gated channel subfamily A member 4). The channel alternates between opened and closed conformations in response to the voltage difference across the membrane (Ramaswami et al. 1990); Po et al. 1993).It can form functional homotetrameric channels and heterotetrameric channels that contain variable proportions of KCNA1, KCNA2, KCNA4, KCNA5, and possibly other family members; channel properties depend on the type of alpha subunits that are part of the channel (Po et al. 1993). Channel properties are modulated by cytoplasmic beta subunits that regulate the subcellular location of the alpha subunits and promote rapid inactivation. In vivo, membranes probably contain a mixture of heteromeric potassium channel complexes. The molecular basis for the inactivation of the channel by the antidepressant, metergoline, has been presented (Bai et al. 2018).	Eukaryota	Metazoa, Chordata	KCNA4 of Homo sapiens
1.A.1.3.1	Large conductance, voltage- and Ca²⁺-activated K⁺ (BK or Slo) channel. Four pairs of RCK1 and RICK2 domains form the Ca²⁺-sensing apparatus known as the "gating ring" in Big Potassium (BK) channel proteins (Savalli et al., 2012). Gating of BK channels does not seem to require a physical gate. Instead, changes in the pore shape and surface hydrophobicity in the Ca²⁺-free state allow the channel to readily undergo hydrophobic dewetting transitions, giving rise to a large free energy barrier for K⁺ permeation (Jia et al. 2018). Voltage-dependent dynamics of the BK channel cytosolic gating ring are coupled to the membrane-embedded voltage sensor (Miranda et al. 2018). Slo channels are targets for insecticides and antiparasitic drugs. Raisch et al. 2021 reported structures of Drosophila Slo in the Ca²⁺-bound and Ca²⁺-free forms and in complex with the fungal neurotoxin verruculogen and the anthelmintic drug emodepside. The architecture and gating mechanism of Slo channels are conserved, but potential insect-specific binding pockets are present. Verruculogen inhibits K⁺ transport by blocking the Ca²⁺-induced activation signal and precludes K⁺ from entering the selectivity filter while emodepside decreases the conductance by suboptimal K⁺ coordination and uncouples ion gating from Ca²⁺ and voltage sensing (Raisch et al. 2021). In neurosecretion, allosteric communication between voltage sensors and Ca²⁺ binding in BK channels is crucially involved in damping excitatory stimuli. Carrasquel-Ursulaez et al. 2022 demonstrated that two arginines in the transmembrane segment S4 (R210 and R213) function as the BK gating charges. The energy landscape of the gating particles is electrostatically tuned by a network of salt bridges contained in the voltage sensor domain (VSD).	Eukaryota	Metazoa, Arthropoda	Ca²⁺-activated K⁺ channel of Drosophila melanogaster
1.A.1.3.2	Large conductance or L-type Ca²⁺ and voltage-activated K⁺ channel (LTCC), α-subunit (subunit α1), BK, BK_Ca, Kca1.1, Slowpoke, Slo1, KCNMA1 or MaxiK (functions with four β-subunits (TC# 8.A.14) encoded by genes KCNMB1-4 and the γ subunit (TC# 8.A.43) in humans (Toro et al. 2013; Li et al. 2016); the positions of beta2 and beta3 have been determined (Wu et al. 2013). The KB channel is inhibited by 3 scorpion toxins, charybda toxin, iberiotoxin and slotoxin. It forms a ''Ca²⁺nanodomain'' complex with Cav1.2 (L-type; 1.A.1.11.4), Cav2.1 (P/Q-type; 1.A.1.11.5) and Cav2.2 (N-type; 1.A.1.11.6) where Ca²⁺ influx through the Cav channel activates BK_Ca (Berkefeld et al., 2006; Romanenko et al., 2006). The RCK2 domain is a Ca²⁺ sensor (Yusifov et al., 2008). Binding of Ca²⁺ to D367 and E535 changes the conformation around the binding site and turns the side chain of M513 into a hydrophobic core, explaining how Ca²⁺ binding opens the activation gate of the channel (Zhang et al., 2010). A structural motif in the C-terminal tail of Slo1 confers carbon monoxide sensitivity to human BK_Cachannels (Williams et al., 2008; Hou et al., 2008). These channels are present in the inner mitochondrial membrane of rat brain (Douglas et al., 2006).The Stress-Axis Regulated Exon (STREX) is responsible for stretch sensitivity. Ca²⁺ binds to two sites. Ca²⁺ binding to the RCK1 site is voltage dependent, but Ca²⁺ binding to the Ca²⁺ bowl is not (Sweet and Cox et al., 2008). Type 1 IP3 receptors activate BKCa channels via local molecular coupling in arterial smooth muscle cells (Zhao et al., 2010). The open structure is known (Yuan et al., 2012). BK_Ca is essential for ER calcium uptake in neurons and cardiomyocytes (Kuum et al., 2012) and link Ca²⁺ signaling to action potential firing and neurotransmitter release via serotonin receptors in many types of neurons (Rothberg 2012). The molecular mechanism of pharmacological activation of BK channels has been discussed by Gessner et al. (2012). The first TMS of the β2-subunit binds to TMS S1 of the α-subunit (Morera et al., 2012). Mutations in Cav1.2 give rise to Timothy syndrome (Dixon et al. 2012). Exhibits low voltage activation by interaction with Cav3 (Rehak et al. 2013) as well as Ca²⁺-gating (Berkefeld and Fakler 2013). Single-channel kinetics have been reported (Geng and Magleby 2014). The γ-subunit has TC# 8.A.43.1.8. RBK channels regulate myogenesis in vascular smooth muscle cells (Krishnamoorthy-Natarajan and Koide 2016). Latorre et al. 2017 reviewed molecular, physiological and pathological aspects of Slo1. The microRNA, mmumiR449a, reduced the mRNA expression levels of transient receptor potential cation channel subfamily A member 1 (TRPA1), and calcium activated potassium channel subunit alpha1 (KCNMA1) and increased the level of transmembrane phosphatase with tension homology (TPTE) in the DRG cells (Lu et al. 2017), thereby reducing pain. The N-terminal sequence determines its modification by β-subunits (Lorca et al. 2017). Inhibition of BKCa negatively alters cardiovascular function (Patel et al. 2018). BKCa may be the target of verteporfin, a benzoporphyrin photosensitizer that alters membrane ionic currents (Huang et al. 2019). Globotriaosylceramide (Gb3) accumulates due to mutations in the gene encoding alpha-galactosidase A. Gb3 deposition in skin fibroblasts impairs KCa1.1 activity and activate the Notch1 signaling pathway, resulting in an increase in pro-inflammatory mediator expression, and thus, contributing to cutaneous nociceptor sensitization as a potential mechanism of FD-associated pain (Rickert et al. 2019). This channel may be present in mitochondria (Parrasia et al. 2019). The Slo3 (TC# 1.A.1.3.5) cytosolic module confers pH-dependent regulation whereas the Slo1 cytosolic module confers Ca²⁺-dependent regulation (Xia et al. 2004). Elevated extracellular Ca²⁺ aggravates iron-induced neurotoxicity because LTCCs mediate iron transport in dopaminergic neurons and this, in turn, results in elevated intracellular Ca²⁺ and further aggravates iron-induced neurotoxicity (Xu et al. 2020). Agonists include BMS-191011, NS1619, NS11021, epoxyeicosatrienoic acid isoforms, while inhibitors include iberiotoxin and penitrem A which have been used to study the system in megakaryocytes and platelets (Balduini et al. 2021). Medicinal plant products can interact with BKCa (Rajabian et al. 2022).	Eukaryota	Metazoa, Chordata	BK_Ca or MaxiK channel of Rattus norvegicus (Q62976)
1.A.1.3.3	Ca²⁺-activated K⁺ channel Slo-1 (Maxi K; BK channel) (ethanol-activated; responsible for intoxication) (Davies et al., 2003); tyrosyl phosphorylation regulates BK channels via cortactin (Tian et al. 2008a), but palmitoylation gates phosphorylation-dependent regulation of BK potassium channels (Tian et al., 2008b). Also regulated by Mg²⁺ which mediates interaction between the voltage sensor and cytosolic domain to activate BK channels (Yang et al., 2007). Modulated by the ss2 subunit (Lee et al., 2010). The structure of the gating ring from the human large-conductance Ca²⁺-gated K⁺ channel has been reported (Wu et al., 2010). Four pairs of RCK1 and RICK2 domains form the Ca²⁺-sensing apparatus known as the "gating ring" in BK channel proteins (Savalli et al., 2012). The dystrophin (Q9TW65) dystrobrevin (Q9Y048) complex controls BK channel localization and muscle activity as well as neurotroansmitter release (Kim et al. 2009, Chen et al. 2011). Syntrophin (Q93646) links various receptors and transporters to the actin cytoskeleton and the dystrophin glycoprotein complex (DGC), and α-catulin (CTN-1; 759 aas, 0 TMSs) facilitates targeting. The BK channel is a tetramer where the pore-forming α-subunit contains seven transmembrane segments (González-Sanabria et al. 2021). It has a modular architecture containing a pore domain with a highly potassium-selective filter, a voltage-sensor domain and two intracellular Ca²⁺ binding sites at the C-terminus. BK is found in the plasma membrane of different cell types, the inner mitochondrial membrane (mitoBK) and the nuclear envelope's outer membrane (nBK). Like BK channels in the plasma membrane (pmBK), the open probability of mitoBK and nBK channels are regulated by Ca²⁺ and voltage and modulated by auxiliary subunits. BK channels share common pharmacology to toxins such as iberiotoxin, charybdotoxin, paxilline, and agonists of the benzimidazole family (González-Sanabria et al. 2021).	Eukaryota	Metazoa, Nematoda	BK K⁺ channel of Caenorhabditis elegans (Q95V25)
1.A.1.3.4	The one or two component intracellularly Na⁺ and Cl^--activated delayed rectifier K⁺ channel, rSlo2.2 (Slack; KCNT1)/r Slo2.1 (Slick; KCNT2; TC# 1.A.1.3.6) provides protection against ischemia (Yuan et al., 2003). The N-terminal domain of Slack determines the formation and trafficking of Slick/Slack heteromeric sodium-activated potassium channels (Chen et al., 2009). Slick and Slack can also form separate homooligomeric channels. These channels are widely distributed in the mammalian CNS and they play roles in slow afterhyperpolarization, generation of depolarizing afterpotentials and in setting and stabilizing the resting potential (Rizzi et al. 2015). The small cytoplasmic protein beta-synuclein TC# 1.C.77.1.2) and the transmembrane protein 263 (TMEM 263; TC# 8.A.101.1.1) are interaction partners of both Slick and Slack channels. The inactive dipeptidyl-peptidase (DPP 10) and the synapse associated protein 102 (SAP 102) are constituents of the Slick and Slack channel complexes (Rizzi et al. 2015).	Eukaryota	Metazoa, Chordata	Slo2 of Rattus norvegicus (Q9Z258)
1.A.1.3.5	Sperm Slo3 high conductance K⁺ channel, activated by voltage and intracellular alkalinization. In sperm, it gives rise to pH-dependent outwardly rectifying K⁺ currents. (required for the ensuing acrosome reaction; activated by phosphatidylinositol 4,5-bisphosphate (PIP(2)) (Tang et al., 2010). The Slo3 cytosolic module confers pH-dependent regulation whereas the Slo1 (TC# 1.A.1.3.2) cytosolic module confers Ca²⁺-dependent regulation (Xia et al. 2004). When mammalian sperm are released in the female reproductive tract, they are incapable of fertilizing the oocyte. They need a prolonged exposure to the alkaline medium of the female genital tract before their flagellum gets hyperactivated and the acrosome reaction can take place, allowing the sperm to interact with the oocyte (de Prelle et al. 2022). Ionic fluxes across the sperm membrane are involved in two essential aspects of capacitation: the increase in intracellular pH and membrane hyperpolarization. The SLO3 potassium channel and the sNHE sodium-proton exchanger are necessary for the capacitation process to occur. As the SLO3 channel is activated by an increase in intracellular pH and sNHE is activated by hyperpolarization, they act together as a positive feedback system (de Prelle et al. 2022).	Eukaryota	Metazoa, Chordata	Slo3 of Mus musculus (O54982)
1.A.1.3.6	Human outward rectifying potassium channel, Slo2.1 (also called KCNT2 and Slick) of 1135 aas. Produces rapidly activating outward rectifier K⁺ currents. Activated by high intracellular sodium and chloride levels. Channel activity is inhibited by ATP and by inhalation of anesthetics such as isoflurane. Inhibited upon stimulation of G-protein coupled receptors such as CHRM1 and GRIA1. Orthologous to 1.A.1.3.4 (Garg et al. 2013) and can form a heteromeric complex with it and several other proteins (see TC# 1.A.1.3.4). Hydrophobic interactions between residues in S5 and the C-terminal end of the pore helix stabilize Slo2.1 channels in a closed state (Suzuki et al. 2016). Despite their apparent high levels of expression, the activities of somatic KNa (Slo2.1 and Slo2.2) channels are tightly regulated by the activity of the Na⁺/K⁺ pump (Gray and Johnston 2021).	Eukaryota	Metazoa, Chordata	Slo2.1 of Homo sapiens
1.A.1.3.7	Slo2.2 sodium-activated potassium channel subfamily T member 1 of 1217 aas and 6 putative N-terminal TMSs plus a P-loop. Cryo electron microscopic structures of the chicken orthologue at 4.5 Å resolution has been solved, revealing a large cytoplasmic gating ring in which resides the Na⁺-binding site and a transmembrane domain that closely resembles voltage-gated K⁺ channels (Hite et al. 2015).	Eukaryota	Metazoa, Chordata	Slo2.2 of Homo sapiens
1.A.1.3.8	SLOwpoke K⁺ channel, SLO-2 or Slo2, of 1107 aas and 6 TMSs, present in motor neurons. It has six putative TMSs with a K⁺-selective pore and a large C-terminal cytosolic domain (Lim et al. 1999). Its requirements for both Cl^- and Ca²⁺ are synergistic and associated with the same functional domain (Yuan et al. 2000) which serves to counteract hypoxia stress when cytoplasmic Cl^- and Ca²⁺ concentrations increase (Yuan et al. 2003; Santi et al. 2003). SLO2 protects from hypoxic injury by increasing the permeability of the mitochondrial inner membrane to K⁺ (Wojtovich et al. 2011). SLO-2 is functionally coupled with CaV1 and regulates neurotransmitter release (Liu et al. 2014). Partially responsible for action potential repolarization during synaptic transmission (Ford and Davis 2014).	Eukaryota	Metazoa, Nematoda	Slo-2 of Caenorhabditis elegans
1.A.1.3.9	Voltage-gated calcium-activated potassium channel of 862 aas and 6 or 7 TMSs.	Eukaryota	Evosea	VIC protein of Entamoeba histolytica
1.A.1.3.10	Calcium-, magnesium- and voltage-activated K⁺ channel, Slo1 (Kcma1; KCNMA, KCNMA1), a BK channel, of 1236 aas and 6 N-terminal TMSs. Its activation dampens the excitatory events that elevate the cytosolic Ca²⁺ concentration and/or depolarize the cell membrane. It therefore contributes to repolarization of the membrane potential, and it plays a key role in controlling excitability in a number of systems. Ethanol and carbon monoxide-bound heme increase channel activation while heme inhibits channel activation (Tang et al. 2003). The molecular structures of the human Slo1 channel in complex with beta4 has been solved revealing four beta4 subunits, each containing two transmembrane helices, encircling Slo1, contacting it through helical interactions inside the membrane. On the extracellular side, beta4 forms a tetrameric crown over the pore. Structures with high and low Ca²⁺ concentrations show that identical gating conformations occur in the absence and presence of beta4, implying that beta4 serves to modulate the relative stabilities of 'pre-existing' conformations rather than creating new ones (Tao and MacKinnon 2019). BK channels show increased activities in Angelman syndrome due to genetic defects in the ubiquitin protein ligase E3A (UBE3A) gene (Sun et al. 2019). It is a large-conductance potassium (BK) channel that can be synergistically and independently activated by membrane voltage and intracellular Ca²⁺. The only covalent connection between the cytosolic Ca²⁺-sensing domain and the TM pore and voltage sensing domains is a 15-residue 'C-linker' which plays a direct role in mediating allosteric coupling between BK domains (Yazdani et al. 2020). Site specific deacylation by the alpha/beta acyl-hydrolase domain-containing protein 17A, ABHD17a (Q96GS6, 310 aas), controls BK channel splice variant activity (McClafferty et al. 2020). Compared with the structure of isolated hSlo1 Ca²⁺ sensing gating rings, two opposing subunits in hBK unfurled, resulting in a wider opening towards the transmembrane region of hBK. In the pore gate domain, two opposing subunits moved downwards relative to the two other subunits (Tonggu and Wang 2022). A gating lever, mediated by S4/S5 segment interactions within the transmembrane domain, rotates to engage and stabilize the open conformation of the S6 inner pore helix upon V sensor activation (Sun and Horrigan 2022). An indirect pathway, mediated by the carboxyl-terminal cytosolic domain (CTD) and C-linker connects the CTD to S6, and stabilizes the closed conformation when V sensors are at rest (Sun and Horrigan 2022). Co-dependent regulation of p-BRAF (TC# 8.A.23.1.48) and the potassium channel KCNMA1 levels drives glioma progression (Xie et al. 2023). Potassium channelopathies associated with epilepsy-related syndromes and directions for therapeutic interventionhave been reviewed (Gribkoff and Winquist 2023). The influx of Ca^2+,mediated by the hypotonic-induced activation of mechanosensitive channels, is a key step for opening both the BK(Ca) and the IK(Ca) channels. The influx of Ca²⁺, mediated by the hypotonic-induced activation of mechanosensitive channels, is a key step for opening both the BK(Ca) and the IK(Ca) (TC# 1.A.1.16.2) channels (Michelucci et al. 2023). Disease-associated KCNMA1 variants decrease circadian clock robustness in channelopathy mouse models (Dinsdale et al. 2023). High-resolution structures illuminate key principles underlying voltage and LRRC26 regulation of Slo1 channels (Kallure et al. 2023).	Eukaryota	Metazoa, Chordata	Kcma1 of Homo sapiens
1.A.1.4.1	K⁺ channel, AKT1; may form heteromeric channels with KC1 (TC # 1.A.1.4.9) (Geiger et al., 2009). Required for seed development and postgermination growth in low potassium (Pyo et al. 2010). Functions optimally with intermediate potassium concentrations (~1 mM) (Nieves-Cordones et al. 2014). In barley, it may play a role in drought resistance (Cai et al. 2019). HAK/KUP/KT8, GrAKT2.1 and GrAKT1.1 potassium channels may function in response to abiotic stress in Gossypium raimondii (Azeem et al. 2021). Plants obtain nutrients from the soil via transmembrane transporters and channels in their root hairs, from which ions radially transport in toward the xylem for distribution across the plant body. Dickinson et al. 2021 determined structures of the hyperpolarization-activated channel, AKT1, from Arabidopsis thaliana, which mediates K⁺ uptake from the soil into plant roots. The structures of AtAKT1, embedded in lipid nanodiscs, show that the channel undergoes a reduction of C4 to C2 symmetry, possibly to regulate its electrical activation.	Eukaryota	Viridiplantae, Streptophyta	AKT1 of Arabidopsis thaliana
1.A.1.4.2	K⁺channel, KDC1 (voltage and pH-dependent; inward rectifying). Does not form homomeric channels. The C-terminus functions in the formation of heteromeric complexes with other potassium alpha-subunits such as KAT1 (1.A.1.4.7) (Naso et al., 2009).	Eukaryota	Viridiplantae, Streptophyta	KDC1 of Daucus carota
1.A.1.4.3	Inward rectifying, pH-independent K⁺ channel, KZM1 (Philippar et al., 2003)	Eukaryota	Viridiplantae, Streptophyta	KZM1 of Zea mays (CAD18901)
1.A.1.4.4	Guard cell outward rectifying K⁺ out channel, GORK, controls leaf stomatal pore opening (by increasing solute content) and closing (by decreasing solute content), which in turn controls gas and water loss (Schroeder, 2003). H₂S signaling not only activates the ion channel proteins located in the guard cell membrane to induce stomatal closure, but also regulates the transcriptional expression and the activity of RuBisCO, a non-stomatal factor to enhance the photosynthetic efficiency of leaves. There is therefore a beneficial balance between the regulation of H₂S signaling on stomatal factors and non-stomatal factors due to drought stress (Zhang et al. 2023).	Eukaryota	Viridiplantae, Streptophyta	GORK of Arabidopsis thaliana (CAC17380)
1.A.1.4.5	Root stelar K⁺ outward rectifying channel, SKOR (involved in K⁺ release into the xylem sap; part of the plant water stress response) (Gaymard et al., 1998). SKOR is an outwardly rectifying K⁺ channel that mediates the delivery of K⁺ from stelar cells to the xylem in the roots, a critical step in the long-distance distribution of K⁺ from roots to the upper parts of the plant. Liu et al. 2006 and Johansson et al. 2006 reported that SKOR channel activity is strictly dependent on intracellular and extracellular K⁺ concentrations. Activation by K⁺ did not affect the kinetics of voltage dependence, indicating that a voltage-independent gating mechanism underlies K⁺ sensing. The C-terminal non-transmembrane region is required for sensing. The intracellular K⁺ sensing mechanism couples SKOR activity to the K⁺ status of the 'source cells', thereby establishing a supply-based unloading system for the regulation of K⁺ distribution (Liu et al. 2006; Johansson et al. 2006). SKOR may be involved in droght resistance in barley (Cai et al. 2019).	Eukaryota	Viridiplantae, Streptophyta	SKOR of Arabidopsis thaliana (AAF26975)
1.A.1.4.6	Heterotetrameric K⁺ channel, KAT2/AKT2/KCT2 (Nieves-Cordones et al. 2014). Forms heteromeric channels (2:2 stoichiometry) with KAT1 (1.A.1.4.7) (Lebaudy et al., 2010) (Properties differ from those of homomeric channels; Xicluna et al., 2007). KAT2 also forms homomeric channels in the plasma membrane (Nieves-Cordones et al. 2014). AKT2 functions in phloem loading and unloading and operates as an inward-rectifying channel that allows H⁺-ATPase-energized K⁺ uptake. Through reversible post-translational modifications, it can also function as an open, K⁺-selective channel, providing energy for transmembrane transport processes. It is present in a complex of several proteins in which it interacts with the receptor-like kinase, MRH1/MDIS2 (Sklodowski et al. 2017). The ortholog in Brassica rapa (Chinese cabbage), KCT2, is induced by stress. It has a TxxTxGYGD motif in the P-domain and a putative cyclic nucleotide-binding-like domain within a long C-terminal region (Zhang et al. 2006). HAK/KUP/KT8, GrAKT2.1 and GrAKT1.1 potassium channels may function in response to abiotic stress in Gossypium raimondii (Azeem et al. 2021).	Eukaryota	Viridiplantae, Streptophyta	AKT2/KAT2 of Arabidopsis thaliana AKT2 (Q38898) KAT2 (Q38849)
1.A.1.4.7	The voltage-sensitive inward rectifying K⁺ channel, KAT1 (similar to 1.A.1.4.3; activated by protein 14-3-3 (AAF87262)) (Sottocornola et al., 2006). May also transport Na⁺ and Cs⁺ (Nakamura and Gaber, 2009). Forms heterotetrameric channels with KAT2 with a stoichiometry of 2:2 (Lebaudy et al., 2010). The pH-sensor is built of a sensory cloud rather than of single key amino acids (Gonzalez et al., 2011). The transmembrane core region of KAT1 is important for its activity in S. cerevisiae, and this involves not only the pore region but also parts of its voltage-sensor domain (Saito et al. 2017). Electromechanical coupling and gating polarity in KAT1 displays a depolarized voltage sensor, which interacts with a closed pore domain directly via two interfaces and indirectly via an intercalated phospholipid. Direct interaction between the sensor and the C-linker hairpin in the adjacent pore subunit is the primary determinant of gating polarity (Clark et al. 2020). Possibly an inward motion of the S4 sensor helix of 5-7 Å underlies a direct-coupling mechanism, driving a conformational reorientation of the C-linker and ultimately opening the activation gate formed by the S6 intracellular bundle. KAT1, and presumably other hyperpolarization-gated plant CNBD channels, can open from an S4-down VSD conformation homologous to the divalent/proton-inhibited conformation of EAG family K⁺ channels (Zhou et al. 2021).	Eukaryota	Viridiplantae, Streptophyta	KAT1 of Arabidopsis thaliana (Q39128)
1.A.1.4.8	Inward rectifying Shaker K⁺ channel SPIK (AKT6) (expressed in pollen, and involved in pollen tube development) (Mouline et al., 2002). The shaker potassium Channel family includes 24 members in Gossypium hirsutum L. (cotton) (Wang et al. 2023).	Eukaryota	Viridiplantae, Streptophyta	SPIK of Arabidopsis thaliana (Q8GXE6)
1.A.1.4.9	The KC1 (KAT3) potassium channel-like subunit; regulates other channels such as AKT1 (1.A.1.4.1) and KAT1 (1.A.1.4.7) (Duby et al., 2008); may form heteromeric channels with AKT1 (Geiger et al., 2009). It forms a tripartite SNARE-K⁺ channel complex which regulates KAT3 channel opening (Honsbein et al., 2009). Tripartite interactions with SNARE (SYP121; SYR1; PEN1) and AKT1 control gating (Grefen et al. 2010). ZKC1 also forms homoleric channels in the endoplasmic reticulum (Nieves-Cordones et al. 2014).	Eukaryota	Viridiplantae, Streptophyta	KC1 of Arabidopsis thaliana (P92960)
1.A.1.4.10	Inward rectifier K⁺ channel AKT1 (45% identical to 1.A.1.4.1; 944aas) (Garciadeblas et al., 2007).	Eukaryota	Viridiplantae, Streptophyta	Akt1 of Physcomitrella patens (A5PH36)
1.A.1.4.11	Potassium channel, KCN11. The UniProt entry included here is not complete. The correct gene ID is Cre06.g278111 in the Chlamydomonas genome database Phytozome. The complete sequence and description of its function are published by Xu et al. (2016). KCN11 is a 6 TMS organelle K⁺ channel found exclusively in the contractile vacuole. It is required for osmoregulation under hypotonic conditions (Xu et al. 2016).	Eukaryota	Viridiplantae, Chlorophyta	KCN11 of Chlamydomonas reinhardtii (Chlamydomonas smithii)
1.A.1.4.12	Synthetic light-sensitive K⁺ channel, BLINK2, of 406 aas and 2 TMSs with a P-loop between the two TMSs (residues 158 - 233). Residues 8 - 142 are derived from residues 403 - 537 of NPH1-1, a light-sensitive ser/thr protein kinase of the oat plant, Avena sativa ( acc # AAC05083); residues 143 - 234 are derived from residues 3 - 94 of the Paramecium bursaria Chlorella virus 1 (PBCV-1) K⁺ channel, Kcv1 (TC# 1.A.1.12.1); residues 235 - 404 derive from residues 506 - 675 of another K⁺ channel protein, KAT1 (TC# 1.A.1.12.1). BLINK1 has been used to manipulate stomatal kinetics to improve carbon assimilation, water use, and growth of A. thaliana (Papanatsiou et al. 2019).			Synthetic light-sensitive K⁺ channel, BLINK2.
1.A.1.4.13	Outwardly rectifying potassium channel, SPORK2, of 843 aas and 6 or 7 TMSs in a 4 +2 + 1 TMS arrangement. The rain tree Samanea saman folds its leaves upon rainfall. Rain perception is in fact a temperature-sensing process, and that Samanea possess an ion channel with a strong temperature sensitivity that is involved in leaf movement (Dreyer and Vergara-Valladares 2023).	Eukaryota	Viridiplantae, Streptophyta	SPORK2 of Samanea saman
1.A.1.5.1	Cyclic nucleotide-gated (CNG) hyperpolarization-activated nonselective cation HCN channel (P_Na⁺ /P_K⁺ ≈ 1.0) of 682 aas and 6 TMSs.	Eukaryota	Metazoa, Chordata	CNG channel of Ictalurus punctatus
1.A.1.5.2	Hyperpolarization-activated and cyclic nucleotide-gated K⁺ channel, HCN (bCNG-1) (P_Na⁺/P_K⁺ ≈ 0.3). The human orthologue (O88703) is 863 aas in length and also catalyzes mixed monovalent cation currents K⁺:Na⁺= 4:1 (Lyashchenko and Tibbs et al., 2008). Biel et al. (2009) presented a detailed review of hyperpolarization-activated cation-channels. They are inhibited by nicotine and epibatidine which bind to the inner pore (Griguoli et al., 2010). They control cardiac and neuronal rhythmicity. HCN channels contain cyclic nucleotide-binding domains (CNBDs) in their C-terminal regions, linked to the pore-forming transmembrane segment with a C-linker. The C-linker couples the conformational changes caused by the direct binding of cyclic nucleotides to the HCN pore opening. Cyclic dinucleotides antagonize the effect of cyclic nucleotides in HCN4 but not in HCN2 channels. Interaction of the C-linker/CNBD with other parts of the channel appears to be necessary for cyclic-dinucleotide binding in HCN4 channels (Hayoz et al. 2017). A conformational trajectory of allosteric gating of the human cone photoreceptor cyclic nucleotide-gated channel has been documented (Hu et al. 2023). The voltage-sensor rearrangements, directly influenced by membrane lipid domains, can explain the heightened activity of pacemaker HCN channels when localized in cholesterol-poor, disordered lipid domains, leading to membrane hyperexcitability and diseases (Handlin and Dai 2023). Opioid-induced hyperalgesia and tolerance are driven by HCN ion channels (Han et al. 2024). It acts as a chaperone that facilitates biogenesis and trafficking of functional transporters heterodimers to the plasma membrane. It forms heterodimers with SLC7 family transporters (SLC7A5, SLC7A6, SLC7A7, SLC7A8, SLC7A10 and SLC7A11), a group of amino-acid antiporters (Parker et al. 2021). Heterodimers function as amino acids exchangers, the specificity of the substrate depending on the SLC7A subunit. Heterodimers SLC3A2/SLC7A6 or SLC3A2/SLC7A7 mediate the uptake of dibasic amino acids (Bröer et al. 2000). The intersubunit interface of the C-linker region regulates the gating polarity of voltage-gated ion channels (Lin et al. 2024).	Eukaryota	Metazoa, Chordata	HCN of Mus musculus
1.A.1.5.3	Heterotetrameric (3A:1B) rod photoreceptor cyclic GMP-gated cation channel, CNGA1 or CNCG or CNCG1 (Zhong et al., 2002) of 686 aas and 6 TMSs. Cyclic nucleotides are required to open the channel. Gating is proposed to be initiated by an anticlockwise rotation of the N-terminal region of the C-linker, which is then, transmitted through the S6 transmembrane helices to the P-helix, and in turn from this to the pore lumen, which opens from 2 to 5 Å, thus allowing for ion permeation (Giorgetti et al. 2005). Defects produce channelopathies (Biel & Michalakis, 2007). A ring of four glutamate residues (Glu363) in the outer vestibule, and a ring of four threonines (Thr360) in the inner vestibule of the pore of CNGA1 channels constitute binding sites for permeating ions (Marchesi et al., 2012). The tetraspanning peripherin-2 (TC# 8.A.40.1.2) links rhodopsin to this cyclic nucleotide-dependent channel in the outer segments of rod photoreceptors. The G266D retinitis pigmentosa mutation in TMS 4 of rhodopsin abolishes binding of peripherin-2 and prevents association with the CNGA1/CNGB1a subunits present in the complex (Becirovic et al. 2014). External protons cause inactivation (Marchesi et al. 2015). CNG transmembrane domains have dynamic structures, undergoing conformational rearrangements (Maity et al. 2015). Moreover, structural heterogeneity of CNGA1 channels has been demonstrated (Maity et al. 2016). The structural basis of calmodulin (CaM) modulation of the rod cyclic nucleotide-gated channel has been elucidated by cryoEM. CaM is a constitutive subunit of the rod channel that ensures high sensitivity in dim light (Barret et al. 2023).	Eukaryota	Metazoa, Chordata	CNG of Homo sapiens Subunit A1 (CNGA1) Subunit B1 (CNGB1)
1.A.1.5.4	Olfactory heteromeric cyclic nucleotide-gated cation (mainly Na⁺, Ca²⁺) channel CNGA2/CNGA4/CNGB1b (present in sensory cilia of olfactory receptor neurons; activated by odorant-induced increases in cAMP concentration) (Michalakis et al., 2006).	Eukaryota	Metazoa, Chordata	CNGA2 complex of Mus musculus CNGA2 (Q62398) CNGA4 (AAI07349) CNGB1b (NP_001288)
1.A.1.5.5	The cyclic nucleotide- and voltage-gated ion (K⁺, Rb⁺, Cs⁺) channel, CNGC1 (inward rectifying). It functions in heavy metal and cation transport, as does CNGC10 (Dreyer and Uozumi, 2011; Zelman et al., 2012). 143 CNGC genes in Glycine max have been identified and classified, and they have been screened for related resistance genes after Fusarium solani infection (Cui et al. 2023).	Eukaryota	Viridiplantae, Streptophyta	CNGC1 of Arabidopsis thaliana (O65717)
1.A.1.5.6	The cyclic nucleotide-gated ion (K⁺, Rb⁺, Cs⁺) channel, CNGC2 (functions in plant defense responses, as does CNGC4) (Zelman et al., 2012).	Eukaryota	Viridiplantae, Streptophyta	CNGC2 of Arabidopsis thaliana (O65718)
1.A.1.5.7	The cyclic nucleotide-gated ion (K⁺, Rb⁺, Cs⁺) channel, HLM1 (CNGC4) It mediates the hypersensitive response (HR) of plants in programmed cell death. Mutants show abnormal cell death and resistance to infection by Pseudomonas syringae (Balagué et al., 2003; Zelman et al., 2012).	Eukaryota	Viridiplantae, Streptophyta	HLM1 of Arabidopsis thaliana (Q94AS9)
1.A.1.5.8	The non-selective cation transporter involved in germination, CNGC3 (Gobert et al., 2006; Zelman et al., 2012).	Eukaryota	Viridiplantae, Streptophyta	CNG3 of Arabidopsis thaliana (Q9SKD7)
1.A.1.5.9	The cyclic nucleotide-gated K⁺ channel, Sp-tetraKCNG (2238 aas) (Galindo et al., 2007)	Eukaryota	Metazoa, Echinodermata	Sp-tetraKCNG of Strongylocentrotus purpuratus (ABN14774)
1.A.1.5.10	Orthologue K⁺/Na⁺ pacemaker channel, Hcn4 (Scicchitano et al., 2012). Hyperpolarization-activated cyclic nucleotide-regulated HCN channels underlie the Na⁺-K⁺ permeable IH pacemaker current. As with other voltage-gated members of the 6-transmembrane KV channel superfamily, opening of HCN channels involves dilation of a helical bundle formed by the intracellular ends of S6, but this is promoted by inward, not outward, displacement of S4. Direct agonist binding to a ring of cyclic nucleotide-binding sites, one of which lies immediately distal to each S6 helix, imparts cAMP sensitivity to HCN channel opening. At depolarized potentials, HCN channels are further modulated by intracellular Mg²⁺ which blocks the open channel pore and blunts the inhibitory effect of outward K⁺ flux. Lyashchenko et al. 2014 showed that cAMP binding to the gating ring enhances not only channel opening but also the kinetics of Mg²⁺ block. Mutations in HCN4 cause sick sinus and the Brugada syndrome, cardiac abnormalities. HCN4 is associated with famiial sinus bradycardia (Boulton et al. 2017). Activation of Hcn4 by cAMP has been reviewed (Porro et al. 2020). The HCN1-4 channel family is responsible for the hyperpolarization-activated cation current If/Ih that controls automaticity in cardiac and neuronal pacemaker cells. Saponaro et al. 2021 presented cryo-EM structures of HCN4 in the presence or absence of bound cAMP, displaying the pore domain in closed and open conformations. Analysis of cAMP-bound and -unbound structures shed light on how ligand-induced transitions in the channel cytosolic portion mediate the effect of cAMP on channel gating and highlighted the regulatory role of a Mg²⁺ coordination site formed between the C-linker and the S4-S5 linker. Comparison of open/closed pore states shows that the cytosolic gate opens through concerted movements of the S5 and S6 transmembrane helices. Furthermore, in combination with molecular dynamics analyses, the open pore structures provide insights into the mechanisms of K⁺/Na⁺ permeation (Saponaro et al. 2021).	Eukaryota	Metazoa, Chordata	Hcn4 of Homo sapiens (Q9Y3Q4)
1.A.1.5.11	Hyperpolarization-activated cyclic nucleotide-gated (HCN) inward current-carrying cationic channel, I(f), (HCN2/HCN4) (Ye and Nerbonne, 2009). Functional interactions between the HCN2 TM region and C-terminal region govern multiple CNB fold-mediated mechanisms, implying that the molecular mechanisms of autoinhibition, open-state trapping, and Quick-Activation include participation of TM region structures (Page et al. 2020). Rhythmic activity in pacemaker cells, as in the sino-atrial node in the heart, depends on the activation of HCN channels. As in depolarization-activated K⁺ channels, the fourth transmembrane segment S4 functions as the voltage sensor in hyperpolarization-activated HCN channels (Wu et al. 2021). S4 in HCN channels moves in two steps in response to hyperpolarizations, and the second S4 step correlates with gate opening (Wu et al. 2021). It is a nuclear hormone receptor that binds estrogens with an affinity similar to that of ESR1/ER-alpha, and activates expression of reporter genes containing estrogen response elements (ERE) in an estrogen-dependent manner (Koyama et al. 2010). It may lack ligand binding ability and has no or only very low ERE binding activity, resulting in the loss of ligand-dependent transactivation ability. Male moujse ejaculation drives sexual satiety and selectively activates Esr2neurons in the BNSTpr of both sexes (Zhou et al. 2023). Changes in binding affinity, rather than changes in cAMP concentration, can modulate HCN channels (Porro et al. 2024).	Eukaryota	Metazoa, Chordata	HCN2/HCN4 channels of Homo sapiens HCN2 (Q9UL51) HCN4 (Q9Y3Q4)
1.A.1.5.12	Cyclic nucleotide-gated cation channel α3 (CNGA3 or CNG3); photoreceptor cGMP-gated channel α-subunit. Also possibly expressed in inner ear cell cells where it binds to an intracellular C-terminal domain of EMILIN1 (Selvakumar et al., 2012). Elastic network model analysis of the CNGA3 channel supports a modular model of allosteric gating, according to which protein domains are quasi-independent: they can move independently but are coupled to each other allosterically (Gofman et al. 2014). An intact S4 is required for proper protein folding and/or assembly involving two glycosylation sites in the endoplasmic reticulum membrane (Faillace et al. 2004). It may function with CNGB3 (TC# 1.A.1.5.37; Q9NQW8; 809 aas and 6 TMSs).	Eukaryota	Metazoa, Chordata	CNGA3 of Homo sapiens (Q16281)
1.A.1.5.13	Trout cyclic nucleotide-gated cation channel α3 (CNGA3 or CNG3). Expressed in inner ear cell cells where it binds to an intracellular C-terminus domain of EMILIN1 (Selvakumar et al., 2012).	Eukaryota	Metazoa, Chordata	CNGA3 of Oncorhynchus mykiss (G9BHJ0)
1.A.1.5.14	Probable cyclic nucleotide-gated ion channel 6 (AtCNGC6) (Cyclic nucleotide- and calmodulin-regulated ion channel 6)	Eukaryota	Viridiplantae, Streptophyta	CNGC6 of Arabidopsis thaliana
1.A.1.5.15	Cyclic nucleotide gated K⁺ channel of 650 aas	Eukaryota	Heterolobosea	Channel of Naegleria gruberi
1.A.1.5.16	Cyanobacterial cyclic nuceotide K⁺ channel of 454 aas (Brams et al. 2014).	Bacteria	Cyanobacteriota	Channel of Trichodesmium erythraeum
1.A.1.5.17	Cyclic nucleotide-gated K⁺channel, SthK, of 430 aas, probably with 6 TMSs in a 2 + 2 + 1 + P-loop + 1 TMS arrangement. The channel is activated by cAMP, not by cGMP, and is highly specific for K⁺ over Na⁺. It has a C-terminal hydrophilic cAMP-binding domain linked to the 6 TMS channel domain (Brams et al. 2014). An SthK C-linker domain is essential for coupling cyclic nucleotide binding to channel opening (Evans et al. 2020). An agonist-dependent conformational change in which residues of the B'-helix displayed outward movement with respect to the symmetry axis of the channel in the presence of cAMP was observed, but not with the partial agonist, cGMP. This conformational rearrangement was observed both in detergent-solubilized SthK and in channels reconstituted into lipid nanodiscs. In addition to outward movement of the B'-helix, channel activation involves upward translation of the cytoplasmic domain with formation of state-dependent interactions between the C-linker and the transmembrane domain (Evans et al. 2020). Three-deminsional structures are available (7RSY_A-D). SthK is active in a sparsely tethered lipid bilayer membranes (Andersson et al. 2023).	Bacteria	Spirochaetota	Channel of Spirochaeta thermophila
1.A.1.5.18	Cyclic nucleotide-gated cation (CNG) channel of 665 aas.	Eukaryota	Metazoa, Arthropoda	CNG of Drosophila melanogaster
1.A.1.5.19	TAX-2 cyclic nucleotide-gated cation channel-B (CNGB) of 800 aas (Wojtyniak et al. 2013).	Eukaryota	Metazoa, Nematoda	TAX-2 CNGB of Caenorhabditis elegans
1.A.1.5.20	TAX-4 cyclic nucleotide-gated cation channel A (CNGA) of 733 aas (Wojtyniak et al. 2013). Li et al. 2017 determined the 3.5 Å resolution single-particle electron cryo-microscopy structure in the cyclic guanosine monophosphate (cGMP)-bound open state. The channel has an unusual voltage-sensor-like domain, accounting for its deficient voltage dependence. A carboxy-terminal linker connecting S6 and the cyclic-nucleotide-binding domain interacts directly with both the voltage sensor-like domain and the pore domain, forming a gating ring that couples conformational changes triggered by cyclic nucleotide binding to the gate. The selectivity filter is lined by the carboxylate side chain of a functionally important glutamate and three rings of backbone carbonyls (Li et al. 2017).	Eukaryota	Metazoa, Nematoda	TAX-4 CNGA of Caenorhabditis elegans
1.A.1.5.21	K⁺ channel protein, PAK2.1 of 543 aas. Contains a cyclic nucleotide-binding domain (Ling et al. 1998; Jegla and Salkoff 1995).	Eukaryota	Ciliophora	PAK2.1 of Paramecium tetraurelia
1.A.1.5.22	K⁺ channel protein, PAK11-MAC of 772 aas. Contains a cyclic nucleotide-binding domain (Ling et al. 1998; Jegla and Salkoff 1995).	Eukaryota	Ciliophora	PAK11-MAC of Paramecium tetraurleia
1.A.1.5.23	Cyclic nuceotide-gated Na⁺ channel of 729 aas and 6 putative TMSs, CNGC19. It is constitutively expressed in roots but induced in leaves and shoots under conditions of salt (NaCl) stress (Kugler et al. 2009). CNG19 and CNGC20 self-associate, form heteromeric complexes, and these complexes arei phosphorylated and stabilized by BOTRYTIS INDUCED KINASE1 (BIK1). Tight control of the CNG19/CNGC20 Ca²⁺ ion channel is important for regulating immunity (Zhao et al. 2021).	Eukaryota	Viridiplantae, Streptophyta	CNGC19 of Arabidopsis thaliana
1.A.1.5.24	Cyclic nucleotide-gated Na⁺ channel of 764 aas and 6 putative TMSs, CNGC20. Induced in shoots in response to salt (NaCl) stress (Kugler et al. 2009). CNGC20 self-associates, forms heteromeric complexes with CNGC19, and is phosphorylated and stabilized by BOTRYTIS INDUCED KINASE1 (BIK1). Tight control of the CNGC20 Ca²⁺ ion channel is important for regulating immunity (Zhao et al. 2021). Spermidine may play a role in salt stress in rice (Saha et al. 2020).	Eukaryota	Viridiplantae, Streptophyta	CNGC20 of Arabidopsis thaliana
1.A.1.5.26	Cyclic nuceotide gated channel of 706 aas, CNGC18. It is the essential Ca²⁺ channel for pollen tube guidance (Gao et al. 2016). MLO5 and MLO9 selectively recruit the Ca²⁺ channel CNGC18-containing vesicles to the plasma membrane through the R-SNARE proteins, VAMP721 and VAMP722 in trans mode. Meng et al. 2020 identified members of the conserved 7 TMS MLO family (expressed in the pollen tube) as tethering factors for Ca²⁺ channels, revealing a mechanism of molecular integration of extracellular ovular cues and selective exocytosis. This work sheds light on the general regulation of MLO proteins in cell responses to environmental stimuli (Meng et al. 2020).	Eukaryota	Viridiplantae, Streptophyta	CNGC18 of Arabidopsis thaliana (Mouse-ear cress)
1.A.1.5.27	CNGC15 of 678 aas and 6 TMSs. In Medicago truncatula, three such channels, CNGC15a, b and c, are required for nuclear calcium oscillations, spiking and subsequent symbiotic responses. These three channels form a complex with the potassium permeable channel, DMI1 (TC# 1.A.1.23.1), in the nuclear envelope. They are expressed in flowers and pods, and mutants in these channels have decreased fertilization rates (Charpentier et al. 2016).		Viridiplantae, Streptophyta	CNG15 of Arabidopsis thaliana
1.A.1.5.28	The cyclic nucleotide-gated cation channel, CNG-1 of 661 aas and 6 TMSs. CNG-1 functions in multiple capacities to link nutritional information with behavioral output (He et al. 2016).	Eukaryota	Metazoa, Nematoda	CNG-1 of Caenorhabditis elegans
1.A.1.5.29	spHCN1 is a pacemaker hyperpolarization-activated cyclic nucleotide-gated (HCN) non-selective cation channel of 767 aas and 6 TMSs that opens due to inward movement of the positive charges in the fourth TMS (S4). This channel is similar to a COOH-terminal-deleted HCN1 channel, suggesting that the main functional differences between spHCN and HCN1 channels are due to differences in their COOH termini (Vemana et al. 2004). These channels open after only two S4s have moved, and S4 motion is rate limiting during voltage activation of spHCN channels (Bruening-Wright et al. 2007). HCN channels regulate electrical activity in the heart and brain. Distinct from mammalian isoforms, the sea urchin (spHCN) channel exhibits strong voltage-dependent inactivation in the absence of cAMP (Idikuda et al. 2018). The voltage sensor undergoes a large downward motion during hyperpolarization (Dai et al. 2019). Sea urchin HCN1 and 2 (TC# 1.A.1.5.33) (spHCN) channels undergo inactivation with hyperpolarization which occurs only in the absence of cyclic nucleotide (Dai et al. 2021). Removing cAMP produces a largely rigid-body rotation of the C-linker relative to the transmembrane domain, bringing the A' helix of the C-linker in close proximity to the voltage-sensing S4 helix. In addition, rotation of the C-linker is elicited by hyperpolarization minus cAMP. Thus, in contrast to electromechanical coupling for channel activation - the A' helix serves to couple the S4-helix movement for channel inactivation, which is likely a conserved mechanism for CNBD-family channels (Dai et al. 2021).	Eukaryota	Metazoa, Echinodermata	HPN1 of Strongylocentrotus purpuratus (Purple sea urchin)
1.A.1.5.30	Hyperpolarization-activated cyclic nucleotide-modulated cation channel splice variant ABs-II of 682 aas and probably 6 TMSs, Ih channel encoded by the PIIH gene (Ouyang et al. 2007).	Eukaryota	Metazoa, Arthropoda	Ih channel of Panulirus interruptus (California spiny lobster) (Palinurus interruptus)
1.A.1.5.31	Multi-domain cation channel with a C-terminal cyclic nucleotide-binding domain; of 465 aas and 6 TMS, LliK. Cyclic nucleotide-gated (CNG) and hyperpolarization-activated cyclic nucleotide-regulated (HCN) channels play roles in phototransduction, olfaction, and cardiac pace making. James et al. 2017 used cryoEM to determine the structure of the intact LliK CNG channel. A short S4-S5 linker connects voltage-sensing and pore domains to produce a non-domain-swapped transmembrane architecture. The conformation of the LliK structure may represent a functional state of this channel family not seen before (James et al. 2017).	Bacteria	Spirochaetota	LliK of Leptospira licerasiae
1.A.1.5.32	HCN1 is a hyperpolarization-activated cyclic nucleotide-gated (HCN) channel of 890 aas and 6 TMSs that opens due to inward movement of the positive charges in the fourth transmembrane domain (S4). These channels open after only two S4s have moved, and S4 motion is rate limiting during voltage activation of spHCN channels (Bruening-Wright et al. 2007). HCN1 exhibits weak selectivity for potassium over sodium ions. It's structure (3.5 Å resolution) is known (Lee and MacKinnon 2017). It contributes to the native pacemaker currents in heart and neurons. It may also mediate responses to sour stimuli. It is inhibited by Cs⁺, zatebradine, capsazepine and ZD7288 (Gill et al. 2004). HCN1 mutational variants include epileptic encephalopathy and common generalized epilepsy. HCN1 has a pivotal function in brain development and control of neuronal excitability (Marini et al. 2018). The interaction with filamin A seems to contribute to localizing HCN1 channels to specific neuronal areas and to modulating channel activity (Gravante et al. 2004). The HCN domain is required for HCN channel cell-surface expression, and it couples voltage- and cAMP-dependent gating mechanisms (Wang et al. 2020). Changes in the local S4 environment provide a voltage-sensing mechanism for mammalian hyperpolarization-activated HCN channels (Bell et al. 2004). Cation leak is an important pathogenic mechanism in HCN1-mediated developmental and epileptic encephalopathy (DEE), and seizures are exacerbated by sodium channel blockers in patients with HCN1 variants that cause cation leak (McKenzie et al. 2023). HCN1 epilepsy is progressing from genetics and mechanisms to precision therapies (Bleakley and Reid 2023). Opioid-Induced Hyperalgesia and Tolerance Are Driven by HCN Ion Channels (Han et al. 2024).	Eukaryota	Metazoa, Chordata	HCN1 of Homo sapiens
1.A.1.5.33	Hyperpolarization-gated and cyclic nucleotide regulated K⁺ channel of 638 aas and 6 TMSs, HCN2, present in the flagellum of sea urchin sperm (Galindo et al. 2005). See also TC# 1.A.1.5.29.	Eukaryota	Metazoa, Echinodermata	HCN2 of Strongylocentrotus purpuratus (Purple sea urchin)
1.A.1.5.34	Cyclic nucleotide-binding domain-containing protein, Cng-3, of 626 aas and 5 - 7 TMSs. It is essential for thermotolerance (Cho et al. 2004). CNG-3 is required in the AWC for adaptation to short (thirty minute) exposures of odor, and contains a candidate PKG phosphorylation site required to tune odor sensitivity (O'Halloran et al. 2017). Cyclic nucleotide-gated channel, CNG-3, determines the timing of transition of temperature preference after a shift in cultivation temperature (Aoki et al. 2018).	Eukaryota	Metazoa, Nematoda	Cng-3 of Caenorhabditis elegans
1.A.1.5.35	The cyclic ABP-gated K⁺ channel, SthK of 430 aas and 6 TMSs in a 2 + 2 + 1 + P-loop +1 TMS arrangement. This channel and others have been studied by high-speed atomic force microscopy (HS-AFM) which has made it possible to characterized the conformational dynamics of single unlabeled transmembrane channels and transporters (Heath and Scheuring 2019).	Bacteria	Spirochaetota	SthK of Spirochaeta thermophila
1.A.1.5.36	Cyclic nucleotide-gated ion channel 17, CNGC17, of 720 aas and 6 TMSs. It forms a functional cation-translocating unit with AHAs that is activated by PSKR1/BAK1 and possibly other BAK1/RLK complexes (Ladwig et al. 2015) and is required for PSK-induced protoplast expansion.	Eukaryota	Viridiplantae, Streptophyta	CNGC17 of Arabidopsis thaliana (Mouse-ear cress)
1.A.1.5.37	Cyclic GMP-gated ion channel β-subunit of 809 aas and 6 TMSs. It may function with CNGA3 (TC# 1.A.1.5.12), but it does not correct mutational defects in the S4 TMS of the α-subunit, CNGA3 (Faillace et al. 2004).	Eukaryota	Metazoa, Chordata	CNGB3 of Homo sapiens
1.A.1.6.1	K⁺ channel, MthK or MVP of 209 aas and 6 TMSs. Voltage-gated potassium-selective channel opened by hyperpolarization (Hellmer and Zeilinger 2003). Mediates K⁺ uptake and sensitivity. The structure and local dynamics of the closed activation gate (lower S6 region) of MVP have been reported (Randich et al. 2014).	Archaea	Euryarchaeota	MthK channel protein of Methanocaldococcus jannaschii (Methanococcus jannaschii)
1.A.1.7.1	Tok1 twin (dual) barrel outward rectifying K⁺ channel with exterme assymmetry which includes an extra 4 N-terminal TMSs for a total of 16 TMSs. (Transports K⁺ and Cs⁺) (Bertl et al., 2003; Roller et al. 2008). TOKs are outwardly rectifying K⁺ channels in fungi with two pore-loops and eight transmembrane spans. Lewis et al. 2020 described the TOKs from four fungal pathogens. These TOKs pass large currents only in the outward direction like this ScTOK. ScTOK, AfTOK1 (Aspergillus fumigatus), and H99TOK (Cryptococcus neoformans grubii) are K⁺-selective and pass current above the K⁺ reversal potential. CaTOK (Candida albicans) and CnTOK (Cryptococcus neoformans neoformans) pass both K⁺ and Na⁺ and conduct above a reversal potential, reflecting the mixed permeability of their selectivity filter. Mutations in CaTOK and ScTOK at sites homologous to those that open the internal gates in classical K⁺ channels are shown to produce inward TOK currents. Possibly the reversal potential determines ion occupancy, and thus, conductivity, of the selectivity filter gate that is coupled to an imperfectly restrictive internal gate, permitting the filter to sample ion concentrations on both sides of the membrane (Lewis et al. 2020). TOK (tandem-pore outward-rectifying K⁺) channels consist of eight TMSs and two pore domains per subunit, organized in dimers. They play a role in cellular K⁺ homeostasis and possibly also in plant-fungus symbioses (Houdinet et al. 2022).	Eukaryota	Fungi, Ascomycota	Tok1 outward rectifier K⁺ channel of Saccharomyces cerevisiae
1.A.1.7.2	AtTPK4 two-pore K⁺ channel 4 (Becker et al., 2004). Asp86 and Asp200 are essential for K⁺ permeation as well as inward rectification (Marcel et al., 2010). Reviewed by González et al. 2014.	Eukaryota	Viridiplantae, Streptophyta	AtTPK4 of Arabidopsis thaliana (AAP82009)
1.A.1.7.3	The 2-pore (4TMS) outward rectifying K⁺ channel, KCO1 or TPK1. Possesses two tandem Ca²⁺-binding EF-hand motifs, and cytosolic free Ca²⁺ (~300 nM) activates (Czempinski et al., 1997). Reviewed by González et al. 2014 and Basu and Haswell 2017.	Eukaryota	Viridiplantae, Streptophyta	KCO1 of Arabidopsis thaliana (Q8LBL1)
1.A.1.7.4	The two pore tonoplast TPK-type K⁺ channel; maintains K⁺ homeostasis in plant cells (Hamamoto et al., 2008); activated by 14-3-3 proteins (Latz et al., 2007).	Eukaryota	Viridiplantae, Streptophyta	TPK1 of Nicotiniana tobacum (A9QMN9)
1.A.1.7.5	Two-pore potassium channel 5 (AtTPK5) (Calcium-activated outward-rectifying potassium channel 5, chloroplastic) (AtKCO5). Reviewed by González et al. 2014.	Eukaryota	Viridiplantae, Streptophyta	TPK5 of Arabidopsis thaliana
1.A.1.7.6	Potassium inward rectifier (Kir)-like channel 3 (AtKCO3)	Eukaryota	Viridiplantae, Streptophyta	KCO3 of Arabidopsis thaliana
1.A.1.7.7	Chloroplast thylakoid two-pore calcium and proton-activated K⁺ channel, TPK3 of 436 aas and 4 TMSs. Mediates ion counterbalancing, influencing photosynthetic llight utilization (Carraretto et al. 2013). Reviewed by González et al. 2014. This two-pore potassium channel modulates the proton motive force (pmf) necessary to convert photochemical energy into physiological functions. It mediates the potassium efflux from the thylakoid lumen required for the regulation of the transmembrane electrical potential, the enhancement of the pH gradient for ATP synthesis, the regulation of electron flow, and pH-mediated photoprotective responses (Carraretto et al. 2013). It has multiple functions under drought stress (Corti et al. 2023).	Eukaryota	Viridiplantae, Streptophyta	TPK3 of Arabidopsis thaliana
1.A.1.7.8	Putative K⁺ channel of 96 aas nd 2 TMSs.	Viruses	Bamfordvirae, Nucleocytoviricota	K⁺ channel of Yellowstone lake phycodnavirus 2
1.A.1.7.9	Outward-rectifier potassium channel TOK1 of 699 aas and 8 TMSs in a 6 + 2 TMS arrangement, where a P-loop may exist between TMSs 5 and 6 as well as TMSs 7 and 8. The system has been characterized and compared with other fungal TOK channels by Lewis et al. 2020	Eukaryota	Fungi, Ascomycota	TOK1 of Neosartorya fumigata (Aspergillus fumigatus)
1.A.1.7.10	TOK1 of 741 aas and 8 TMSs in a 6 + 2 TMS arrangement with P-loops between TMSs 5 and 6 as well as 7 and 8. It transports both Na⁺ and K⁺, and has been characterized by Lewis et al. 2020. See 1.A.7.1.1 for a more detailed description.	Eukaryota	Fungi, Ascomycota	TOK1 of Candida albicans (Yeast)
1.A.1.8.1	TWIK-1 (KCNK1, HOHO1, KCNO1) inward rectifier K⁺ channel (Enyedi and Czirják, 2010) expressed in the distal nephron segments (Orias et al. 1997). Lipid tails from both the upper and lower leaflets can partially penetrate into the pore (Aryal et al. 2015). The lipid tails do not sterically occlude the pore, but there is an inverse correlation between the presence of water within the hydrophobic barrier and the number of lipids tails within the lining of the pore (Aryal et al. 2015).	Eukaryota	Metazoa, Chordata	TWIK-1 of Mus musculus
1.A.1.8.2	TASK-2 (KCNK5) two-pore domain, pH-sensitive, voltage-insensitive, outward rectifying K⁺ channel (K⁺ > Rb⁺ >> Cs⁺ > NH₄⁺ > Na⁺ ≈ Li⁺), present in renal epithelia. Regulated [inhibited] via group 1 metabolotropic glutamate receptors and by inositol phosphates (Chemin et al., 2003). TASK-2 gating is controlled by changes in both extra- and intracellular pH through separate sensors: arginine 224 and lysine 245, located at the extra- and intracellular ends of transmembrane domain 4, respectively. TASK-2 is inhibited by a direct effect of CO2 and is regulated by and interacts with G protein subunits. TASK-2 takes part in regulatory adjustments and is a mediator in the chemoreception process in neurons of the retrotrapezoid nucleus where its pH_i sensitivity could be important in regulating excitability and therefore signalling of the O₂/CO₂ status. Extracellular pH increases, brought about by HCO₃^-efflux from proximal tubule epithelial cells may couple to TASK-2 activation to maintain electrochemical gradients favourable to HCO₃^- reabsorption. TASK-2 is expressed at the basolateral membrane of proximal tubule cells (López-Cayuqueo et al. 2014). Mutations are associated with the Balkan Endemic Nephropathy (BEN) chronic tubulointerstitial renal disease (Reed et al. 2016). pH sensing in TASK2 channels is conferred by the combined action of several charged residues in the large extracellular M1-P1 loop (Morton et al. 2005). TASK-2, a member of the TALK subfamily of K2P channels, is opened by intracellular alkalization, leading the deprotonation of the K245 residue at the end of the TM4 helix. This charge neutralization of K245 may be sensitive or coupled to the fenestration state. The most important barrier for ion transport under K245⁺ and open fenestration conditions is the entrance of the ions into the channel (Bustos et al. 2020).	Eukaryota	Metazoa, Chordata	TASK-2 of Homo sapiens
1.A.1.8.3	The 2P-domain K⁺ channel, TWIK 2 (functions in cell electrogenesis (Patel et al., 2000).	Eukaryota	Metazoa, Chordata	TWIK2 of Homo sapiens (Q9Y257)
1.A.1.8.4	Potassium channel subfamily K member 5, Kcnk5a, of 513 aas and 6 TMSs. It is 50% identical with the human ortholog. Genome analysis revealed that its genetic structure in the yellowfin seabream (Acanthopagrus latus) is influenced by a variety of factors including salinity gradients, habitat distance, and ocean currents (Wang et al. 2024)	Eukaryota	Metazoa, Chordata	KCNK5A of Danio rerio (Zebrafish) (Brachydanio rerio)
1.A.1.9.1	TREK-1 (KCNK2) K⁺ channel subunit (Regulated by group 1 metabotropic glutamate receptors and by diacylglycerols and phosphatidic acids) (Chemin et al., 2003). TREK-1, TREK-2 and TRAAK are all regulated by lysophosphatidic acid, converting these mechano-gated, pH voltage-sensitive channels into leak conductances (Chemin et al., 2005). The mammalian K2P2.1 potassium channel (TREK-1, KCNK2) is highly expressed in excitable tissues, where it plays a key role in the cellular mechanisms of neuroprotection, anaesthesia, pain perception and depression (Cohen et at., 2008). Alternative translation initiation in rat brain yields K2P2.1 potassium channels permeable to sodium (Thomas et al. 2008). The crystal structure of the human 2-pore domain K⁺ channel, K2P1 has been solved (Miller and Long, 2012). Multiple modalities converge on a common gate to control K2P channel function (Bagriantsev et al., 2011). TREK-1 mediates fast and slow glutamate release in astrocytes upon GPCR activation (Woo et al. 2012). It is a mechanosensitive K⁺ channel, present in rat bladder myocytes, which is activated by swelling and arachidonic acid (Fukasaku et al. 2016). The M2-hinges of TREK-1 and TREK-2 channels control their macroscopic current, subcellular localization and gating (Zhuo et al. 2017). The human ortholog has acc # O95069 and has an additional N-terminal 15 aas. BL-1249, a compound from the fenamate class of nonsteroidal anti-inflammatory drugs, is known to activate K2P2.1(TREK-1), the founding member of the thermo- and mechanosensitive TREK subfamily (Pope et al. 2018). Spadin and arachidonic acid, are known to suppress and activate TREK-1 channels, respectively (Pappa et al. 2020). Membrane phospholipids control gating of the mechanosensitive potassium leak channel, TREK1 (Schmidpeter et al. 2023). A photoswitchable inhibitor of TREK channels controls pain in wild-type intact freely moving animals (Landra-Willm et al. 2023). TREK-1 is an anesthetic-sensitive K⁺ channel (Spencer et al. 2023). Covalent chemogenetic K_2P channel activators have been developed (Deal et al. 2024). K_2P potassium channels regulate excitability by affecting the cellular resting membrane potential in the brain, cardiovascular system, immune cells, and sensory organs. They are important in anesthesia, arrhythmia, pain, hypertension, sleep, and migraine headaches. CATKLAMP (covalent activation of TREK family K⁺ channels to clamp membrane potential) leverages the discovery of a K_2P modulator pocket site that reacts with electrophile-bearing derivatives of a TREK subfamily small-molecule activator, ML335, to activate the channel irreversibly. Deal et al. 2024 showed that CATKLAMP can be used to probe fundamental aspects of K_2P function, as a switch to silence neuronal firing, and is applicable to all TREK subfamily members.	Eukaryota	Metazoa, Chordata	TREK-1 of Mus musculus (P97438)
1.A.1.9.2	KCNK3 K⁺ channel (TASK1, OAT1, TBAK1) (the K⁺ leak conductance). TASK1 and 3 may play roles in nontumorigenic primary hyperaldosteronism (Davies et al., 2008). KCNK3/9/15 expression limits membrane depolarization and depolarization-induced secretion at least in part by maintaining intracellular K⁺ (Huang et al. 2011). TWIK-related acid-sensitive potassium (TASK) channels, members of the two pore domain potassium (K2P) channel family, are found in neurons, cardiomyocytes and vascular smooth muscle cells, where they are involved in the regulation of heart rate, pulmonary artery tone, sleep/wake cycles and responses to volatile anaesthetics (Rödström et al. 2020). K2P channels regulate the resting membrane potential, providing background K⁺ currents controlled by numerous physiological stimuli. Unlike other K2P channels, TASK channels are able to bind inhibitors with high affinity, exceptional selectivity and very slow compound washout rates. In general, potassium channels have an intramembrane vestibule with a selectivity filter situated above and a gate with four parallel helices located below, but the K2P channels studied so far all lack a lower gate. Rödström et al. 2020 presented the X-ray crystal structure of TASK-1, and showed that it contains a lower gate designated 'X-gate', created by interaction of the two crossed C-terminal M4 transmembrane helices at the vestibule entrance. This structure is formed by six residues ((243)VLRFMT(248)) that are essential for responses to volatile anaesthetics, neurotransmitters and G-protein-coupled receptors. Mutations within the X-gate and the surrounding regions affect both the channel-open probability and the activation of the channel by anaesthetics. Structures of TASK-1 bound to two high-affinity inhibitors showed that both compounds bind below the selectivity filter and are trapped in the vestibule by the X-gate, which explains their exceptionally low washout rates (Rödström et al. 2020). TWIK-related acid-sensitive K⁺ channel 2 promotes renal fibrosis by inducing cell-cycle arrest (Zhang et al. 2022). KCNK3 dysfunction plays a role in dasatinib-associated pulmonary arterial hypertension and endothelial cell dysfunction (Ribeuz et al. 2024).	Eukaryota	Metazoa, Chordata	TASK1 or KCNK3 of Homo sapiens (AAG29340)
1.A.1.9.2.3	K_2P channel, TALK-2, KCNK17, TASK4 of 463 aas. Trichome responses to elevated elemental stress in cation exchanger (CAX) mutants have been recorded (Guo et al. 2024).	Eukaryota	Viridiplantae, Streptophyta	TALK-2 of Arabidopsis thaliana
1.A.1.9.3	Neuronal 2-P (4 TMS) domain K⁺ membrane tension-gated channel, TRAAK (stimulated by arachidonic acid and polyunsaturated fatty acids (Fink et al., 1998). The crystal structures of conductive and nonconductive human K2P TRAAK K⁺ channel has been solved (Brohawn et al., 2012; Brohawn et al. 2014). Regulated by mechanical deformation of the membrane and temperature as well as polyunsaturated fatty acids (Brohawn et al., 2012). Multiple modalities converge on a common gate to control K2P channel function (Bagriantsev et al., 2011). In the non-conductive state, a lipid acyl chain accesses the channel cavity through a 5 Å-wide lateral opening in the membrane inner leaflet and physically blocks ion passage. In the conductive state, rotation of transmembrane helix 4 about a central hinge seals the intramembrane opening, preventing lipid block of the cavity and permitting ion entry. Additional rotation of a membrane interacting TM2-TM3 segment, unique to mechanosensitive K2Ps, against TM4 may further stabilize the conductive conformation. Comparison of the structures provodes a biophysical explanation for TRAAK mechanosensitivity--an expansion in cross-sectional area up to 2.7 nm² in the conductive state is expected to create a membrane-tension-dependent energy difference between conformations that promotes force activation (Brohawn et al. 2014). TM helix straightening and buckling may underlie channel activation (Lolicato et al. 2014). A lipid chain blocks the conducting path in the closedBrohawn et al. 2014). Regulated by mechanical deformation of the membrane and temperature as well as polyunsaturated fatty acids (Brohawn et al., 2012). Multiple modalities converge on a common gate to control K2P channel function (Bagriantsev et al., 2011). In the non-conductive state, a lipid acyl chain accesses the channel cavity through a 5 Å-wide lateral opening in the membrane inner leaflet and physically blocks ion passage. In the conductive state, rotation of transmembrane helix 4 about a central hinge seals the intramembrane opening, preventing lipid block of the cavity and permitting ion entry. Additional rotation of a membrane interacting TM2-TM3 segment, unique to mechanosensitive K2Ps, against TM4 may further stabilize the conductive conformation. Comparison of the structures provodes a biophysical explanation for TRAAK mechanosensitivity--an expansion in cross-sectional area up to 2.7 nm² in the conductive state is expected to create a membrane-tension-dependent energy difference between conformations that promotes force activation (Brohawn et al. 2014). TM helix straightening and buckling may underlie channel activation (Lolicato et al. 2014). A lipid chain blocks the conducting path in the closedBrohawn et al. 2014). TM helix straightening and buckling may underlie channel activation (Lolicato et al. 2014). A lipid chain blocks the conducting path in the closed state (Rasmussen 2016).	Eukaryota	Metazoa, Chordata	TRAAK of Mus musculus (O88454)
1.A.1.9.4	Outward rectifying mechanosensitive 2-P (4 TMS) domain K⁺ channel, TREK-2 (KCNKA; KCNK10; K2P10). Activated by membrane stretch, acidic pH, arachidonic acid and unsaturated fatty acids. Dong et al. 2015 described crystal structures of the human TREK-2 channel (up to 3.4 angstrom resolution) in two conformations and in complex with norfluoxetine, the active metabolite of fluoxetine (Prozac) and a state-dependent blocker of TREK channels. Norfluoxetine binds within intramembrane fenestrations found in only one of these two conformations. Channel activation by arachidonic acid and mechanical stretch involves conversion between these states through movement of the pore-lining helices. This provides an explanation for TREK channel mechanosensitivity, regulation by diverse stimuli, and possible off-target effects of the serotonin reuptake inhibitor Prozac (Dong et al. 2015). The unique gating properties of TREK-2 and the mechanisms by which extracellular and intracellular stimuli harness pore gating allosterically have been studied (Zhuo et al. 2016). TREK-2 moves from the "down" to the "up" conformation in direct response to membrane stretch. Aryal et al. 2017 showed how state-dependent interactions with lipids affect the movement of TREK-2, and how stretch influences both the inner pore and selectivity filter. They also demonstrated why direct pore block by lipid tails does not represent theprincipal mechanism of mechanogating (Aryal et al. 2017). The M2-hinges of TREK-1 and TREK-2 channels control their macroscopic current, subcellular localization and gating (Zhuo et al. 2017). TREK-2 responds to a diverse range of stimuli. Two states, "up" and "down", are known from x-ray structural crystallographic studies and have been suggested to differ in conductance. Brennecke and de Groot 2018 found that the down state is less conductive than the up state. The introduction of membrane stretch in the simulations shifts the state of the channel toward an up configuration. Membrane pressure changes the conformation of the transmembrane helices directly and consequently also influences the channel conductance (Brennecke and de Groot 2018). 3-d structures are known (PDB 4XDJ_!-D). Phosphatidyl-(3,5)-bisphosphate (PI(3,5)P2) activates (Kirsch et al. 2018).	Eukaryota	Metazoa, Chordata	TREK-2 of Rattus norvegicus (Q9JIS4)
1.A.1.9.5	The TWiK family muscle K⁺ channel protein 18 (TWiK or Two-P domain K⁺ channel family) (controls muscle contraction and organismal movement; Kunkel et al., 2000)	Eukaryota	Metazoa, Nematoda	TWK-18 of Caenorhabditis elegans (Q18120)
1.A.1.9.6	The pH-sensitive 2 pore (4 TMS) K⁺ channel, TAQLK2, TALK-2 or TASK-4 (Expressed in liver, lung, pancreas and other tissues; Decher et al., 2001). The response of the tandem pore potassium channel TASK-3 (TC# 1.A.1.9.11) (K(2P)9.1) to voltage involves gating at the cytoplasmic mouth (Ashmole et al., 2009). Models have revealed the convergence of amino acid regions that are known to modulate anesthetic activity onto a common three-dimensional cavity that forms a putative anesthetic binding site in tandem pore potassium channels (Bertaccini et al. 2014). Ion occupancy of the selectivity filter controls opening of a cytoplasmic gate in the K_2P channel TALK-2 (Neelsen et al. 2024).	Eukaryota	Metazoa, Chordata	TASK-4 of Homo sapiens (Q96T54)
1.A.1.9.7	Sup-9 K⁺ channel of 329 aas and 6 TMSs. It is involved in coordination of muscle contraction (de la Cruz et al. 2003). Activity is regulated by Sup-18 (de la Cruz et al. 2014) and by Unc-93 (TC# 2.A.1.5.8). It may also be regulated by Sup-10 (Q17374); it may be a suppressor of Unc-93 (de la Cruz et al., 2003). Mutation of a single residue promotes gating of this channel and of several vertebrate and invertebrate two-pore domain potassium channels (Ben Soussia et al. 2019).	Eukaryota	Metazoa, Nematoda	Sup-9 of Caenorhabditis elegans (O17185)
1.A.1.9.8	TWiK family of potassium channels protein 9	Eukaryota	Metazoa, Nematoda	twk-9 of Caenorhabditis elegans
1.A.1.9.9	TWiK family of potassium channels protein 12	Eukaryota	Metazoa, Nematoda	Twk-12 of Caenorhabditis elegans
1.A.1.9.10	Potassium channel subfamily K member 16 (2P domain potassium channel Talk-1) (TWIK-related alkaline pH-activated K⁺ channel 1) (TALK-1 or KCNK16) of 309 aas and 6 TMSs. It is an outward rectifying potassium channel that produces rapidly activating and non-inactivating outward rectifier K⁺ currents. Allosteric coupling between transmembrane segment 4 and the selectivity filter regulates gating by extracellular pH (Tsai et al. 2022).	Eukaryota	Metazoa, Chordata	KCNK16 of Homo sapiens
1.A.1.9.11	pH-dependent, voltage-insensitive, background potassium channel protein involved in maintaining the membrane potential, KCNK9, K2P9.1 or TASK3 (TASK-3) of 374 aas (Huang et al. 2011). Terbinafine is a selective activator of TASK3 (Wright et al. 2017). The response of the tandem pore potassium channel TASK-3 to voltage involves gating at the cytoplasmic mouth (Ashmole et al., 2009). TASK-3 is involved in several physiological and pathological processes including sleep/wake control, cognition and epilepsy (Tian et al. 2019). N-(2-((4-nitro-2-(trifluoromethyl)phenyl)amino)ethyl)benzamide (NPBA) is an activator (Tian et al. 2019). KCC2 regulates neuronal excitability and hippocampal activity via interaction with Task-3 channels (Goutierre et al. 2019). A biguanide compound, CHET3, is a highly selective allosteric activator, and TASK-3 is a druggable target for treating pain (Liao et al. 2019). This channel may be present in mitochondria (Parrasia et al. 2019). Differential hydroxymethylation levels in the DNA of patient-derived neural stem cells implicated altered cortical development in bipolar disorder syndrome possibly altering KCNK9 expression (Kumar et al. 2023).	Eukaryota	Metazoa, Chordata	KCNK9 or TASK3 of Homo sapiens
1.A.1.9.12	Potassium channel subunit of 330 aas. No channel activity was observed in heterologous systems. It probably needs to associate with other proteins (i.e., KCNK3 and KCNK9) to form a functional channel (Huang et al. 2011).	Eukaryota	Metazoa, Chordata	KCNK15 of Homo sapiens
1.A.1.9.13	The Kcnk10a (TREK-2A) K⁺ channel of 569 aas and 6 TMSs. It localizes in the brain and seems to regulate reproduction (Loganathan et al. 2017).	Eukaryota	Metazoa, Chordata	TREK-2A of Danio rerio (Zebrafish) (Brachydanio rerio)
1.A.1.9.14	Open rectifier K⁺ channel 1, isoform D of 1001 aas and 6 TMSs, Ork1.	Eukaryota	Metazoa, Arthropoda	ORK1 of Drosophila melanogaster (Fruit fly)
1.A.1.10.1	Voltage-sensitive Na⁺ channel, Na_V1.7 (Cox et al., 2006). The human orthologue, SCN3A or Nav1.3, when mutated causes cryptogenic pediatric partial epilepsy (Holland et al., 2008; Zaman et al. 2020). Batrachotoxin (BTX) is a steroidal alkaloid neurotoxin that activates NaV channels through interacting with transmembrane domain-I-segment 6 (IS6) of these channels. Ginsenoside inhibits BTX binding (Lee et al. 2008). VGSCs are heterotrimeric complexes consisting of a single pore-forming alpha subunit joined by two beta subunits, a noncovalently linked beta1 or beta3 and a covalently linked beta2 or beta4 subunit (Hull and Isom 2017). The binding mode and functional components of the analgesic-antitumour peptide from Buthus martensii Karsch to human voltage-gated sodium channel 1.7 have been characterized (Zhao et al. 2019). Dvorak et al. 2021 developed allosteric modulators of ion channels by targeting their PPI interfaces, particularly in the C-terminal domain of the Nav, with auxiliary proteins. Fenestrations are key functional regions of Nav that modulate drug binding, lipid binding, and influence gating behaviors (Gamal El-Din and Lenaeus 2022). Compartment-specific localizations and trafficking mechanisms for VGSCs are regulated separately to modulate membrane excitability in the brain (Liu et al. 2022). Naview is a library for drawing and annotating voltage-gated sodium channel membrane diagrams (Afonso et al. 2022). Deltamethrin (DLT) is a type-II pyrethroid ester insecticide used in agricultural and domestic applications as well as in public health. Exposure to DLT produced a differential and dose-dependent stimulation of peak Na+ currents, Conversely, tefluthrin (Tef), a type-I pyrethroid insecticide, accentuates I(Na) with a slowing in inactivation time course of the current (Lin et al. 2022). MicroRNA-335-5p suppresses voltage-gated sodium channel expression and may be a target for seizure control (Heiland et al. 2023). Voltage-gated sodium channels are enhancing factors in the metastasis of metastatic prostate cancer cells (Yildirim-Kahriman 2023). Decreasing microtubule detyrosination modulates Nav1.5 subcellular distribution and restores sodium current in Mdx cardiomyocytes (Nasilli et al. 2024).	Eukaryota	Metazoa, Chordata	Voltage-sensitive Na⁺ channel of Rattus norvegicus
1.A.1.10.2	Na⁺ channel, α-subunit, SCAP1, of 1993 aas and 24 TMSs (Dyer et al. 1997).	Eukaryota	Metazoa, Mollusca	SCAP1 from Aplysia californica (P90670)
1.A.1.10.3	Ca²⁺-regulated heart Na⁺ channel, Na_v1.5, SCN5A or INa channel of 2016 aas. The COOH terminus functions in the control of channel inactivation and in pathologies caused by inherited mutations that disrupt it (Glaaser et al., 2006); regulated by ProTx-II Toxin (Smith et al. 2007), telethonin, the titin cap protein (167aas; secreted protein; O15273) (Mazzone et al., 2008), and the Mog1 protein, a central component of the channel complex (Wu et al., 2008). Na_v1.5, the principal Na⁺ channel in the heart, possesses an ankyrin binding site, and direct interaction with ankyrin-G is required for the expression of Na_v1.5 at the cardiomyocyte cell surface (Bennett and Healy, 2008; Lowe et al., 2008). Mutations cause type 3 long QT syndrome and type 1 Brugada syndrome, two distinct heritable arrhythmia syndromes (Mazzone et al., 2008; Kapplinger et al. 2010; Wang et al. 2015). SCN5A mutations causing arrhythmic dilated cardiomyopathy, commonly localized to the voltage-sensing mechanism, and giving rise to gating pore currents (currents that go through the voltage sensor) have been identified (McNair et al., 2011; Moreau et al., 2014). Patients with Brugada syndrome are prone to develop ventricular tachyarrhythmias that may lead to syncope, cardiac arrest or sudden cardiac death (Sheikh and Ranjan 2014) and (Kapplinger et al. 2015). Mutations causing disease have been identified (Qureshi et al. 2015). These give rise to arrhythias and cardiomyopathies (Moreau et al. 2015). Mutations that cause relative resistance to slow inactivation have been identified (Chancey et al. 2007). Green tea catechins are potential anti-arrhythmics because of the significant effect of Epigallocatechin-3-Gallate (E3G) on cardiac sodium channelopathies that display a hyperexcitability phenotype (Boukhabza et al. 2016). A mutatioin, R367G, causes the familial cardiac conductioin disease (Yu et al. 2017). The C-terminal domain of calmodulin (CaM) binds to an IQ motif in the C-terminal tail of the alpha-subunit of all NaV isoforms, and contributes to calcium-dependent pore-gating in some (Isbell et al. 2018). Ventricular fibrillation in patients with Brugada syndrome (BrS) is often initiated by premature ventricular contractions, and the presence of SCN5A mutations increases the risk upon exposure to sodium channel blockers in patients with or without baseline type-1 ECG (Amin et al. 2018). A mutation (R367G) is associated with familial cardiac conduction disease (Yu et al. 2017). Among ranolazine, flecainide, and mexiletine, only mexiletine restored inactivation kinetics of the currents of the mutant protein, A1656D (Kim et al. 2019). Epigallocatechin-3-gallate (EGCG) is protective against cardiovascular disorders due in part to its action on multiple molecular pathways and transmembrane proteins, including the cardiac Nav1.5 channels (Amarouch et al. 2020). An SCN1B variant affects both cardiac-type (NaV1.5) and brain-type (NaV1.1) sodium currents and contributes to complex concomitant brain and cardiac disorders (Martinez-Moreno et al. 2020). Mice null for Scn1b, which encodes NaV beta1 and beta1b subunits, have defects in neuronal development and excitability, spontaneous generalized seizures, cardiac arrhythmias, and early mortality (Martinez-Moreno et al., 2020; Martinez-Moreno et al. 2020). The structural basis of cytoplasmic NaV1.5 and NaV1.4 regulation has been reviewed (Nathan et al. 2021). Fibroblast growth factor 21 ameliorates NaV1.5 and Kir2.1 channel dysregulation in human AC16 cardiomyocytes (Li et al. 2021). The interaction of Nav1.5 with MOG1 (RANGRF), a Ran guanine nucleotide release factor and chaparone, provides a possible molecular mechanism for Brugada syndrome (Xiong et al. 2021). Arrhythmic phenotypes are a defining feature of dilated cardiomyopathy-associated SCN5A variants (Peters et al. 2021). A SCN5A genetic variant, Y739D, is associated with Brugada syndrome (Zaytseva et al. 2022). Melatonin treatment causes an increase of conduction via enhancement of sodium channel protein expression and increases of sodium current in the ventricular myocytes (Durkina et al. 2022). Quantification of Nav1.5 expression has been published (Adams et al. 2022). Cardiac sodium channel complexes play a role in arrhythmia, and the structural and functional roles of the beta1 and beta3 subunits have been determined (Salvage et al. 2022). Brugada Syndrome (BrS) treatment is electrocardiography with ST-segment elevation in the direct precordial derivations. The clinical presentation of the disease is highly variable. Patients can remain completely asymptomatic, but they can also develop episodes of syncope, atrial fibrillation (AF), sinus node dysfunction (SNF), conduction disorders, asystole, and ventricular fibrillation (VF). This disease is caused by mutations in the genes responsible for the potential action of cardiac cells. The most commonly involved gene is SCN5A, which controls the structure and function of the heart's sodium channel (Brugada 2023).	Eukaryota	Metazoa, Chordata	Na_v1.5 of Homo sapiens (Q14524)
1.A.1.10.4	The skeletal muscle Na⁺ channel, Na_V1.4 of 1836 aas and 24 TMSs. Mutations in charged residues in the S4 segment cause hypokalemic periodic paralysis (HypoPP)) due to sustained sarcolemmal depolarization (Struyk and Cannon 2007; Sokolov et al., 2007; Groome et al. 2014). Also causes myotonia; regulated by calmodulin which binds to the C-terminus of Na_v1.4 (Biswas et al., 2008). Na_V1.4 gating pores are permeable to guanidine as well as Na⁺ and H⁺ (Sokolov et al., 2010). The R669H mutation allows transmembrane permeation of protons, but not larger cations, similar to the conductance displayed by histidine substitution at Shaker K⁺ channel S4 sites (Struyk and Cannon 2007). The mechanism of inactivation involves transient interactions between intracellular domains resulting in direct pore occlusion by the IFM motif and concomitant extracellular interactions with the beta1 subunit (Sánchez-Solano et al. 2016). Potassium-sensitive hypokalaemic and normokalaemic periodic paralysis are inherited skeletal muscle diseases in humans, characterized by episodes of flaccid muscle weakness. They are caused by single mutations in positively charged residues ('gating charges') in the S4 transmembrane segment of the voltage sensor of the voltage-gated sodium channel Nav1.4 or the calcium channel Cav1.1. Mutations of the outermost gating charges (R1 and R2) cause hypokalaemic periodic paralysis by creating a pathogenic gating pore in the voltage sensor through which cations leak in the resting state. Mutations of the third gating charge (R3) cause normokalaemic periodic paralysis owing to cation leak in both activated and inactivated states (Jiang et al. 2018). The neurotoxic cone snail peptide μ-GIIIA specifically blocks skeletal muscle voltage-gated sodium (Na_V1.4) channels (Leipold et al. 2017). the cryo-electron microscopy structure of the human Na_v1.4-β1 complex at 3.2-Å resolution. Accurate model building was made for the pore domain, the voltage-sensing domains, and the β1 subunit (Pan et al. 2018) provided insight into the molecular basis for Na⁺ permeation and kinetic asymmetry of the four repeats. Structural analysis of reported functional residues and disease mutations corroborates an allosteric blocking mechanism for fast inactivation of Na_v channels. the S4-S5L of the DI, DII and DIII domains allosterically modulate the activation gate and stabilize its open state (Malak et al. 2020). The structural basis of cytoplasmic NaV1.5 and NaV1.4 regulation has been reviewed (Nathan et al. 2021). Mutations in SCN4A give rise to a variety of pathological conditions (Sun et al. 2021). Hypokalemic periodic paralysis (HypoPP) is a rare autosomal dominant disease caused by mutations in either calcium or sodium transmembrane voltage-gated ion channels in the ER of skeletal muscle (Calise et al. 2023). Diverse biophysical mechanisms for the voltage-gated sodium channel Na_v1.4 variants are associated with myotonia (Tikhonova et al. 2024).	Eukaryota	Metazoa, Chordata	Na_V1.4 of Homo sapiens (P35499)
1.A.1.10.5	Voltage-sensitive Na⁺ channel, type 9, α-subunit, Nav1.7 or SCN9A (orthologous to 1.A.1.10.1). Loss of function, resulting from point mutations, results in a channelopathy called Congenital Insensitivity to Pain (CIP) (He et al. 2018), that causes the congenital inability to experience pain (Cregg et al., 2010; Kleopa, 2011). An S241T mutation causes inherited erythromelalgia IEM; erythermalgia, an autosomal dominant neuropathy characterized by burning pain in the extremities in response to mild warmth (due to altered gating) (Lampert et al., 2006; Drenth and Waxman, 2007). Gain-of-function mutations in the Na(v)1.7 channel lead to DRG neuron hyperexcitability associated with severe pain, whereas loss of the Na(v)1.7 channel in patients leads to indifference to pain (Dib-Hajj et al., 2007). Blocked by 1-benzazepin-2-one (Kd = 1.6 nM) (Williams et al., 2007). Mutations in the Nav1.7 Na channel α-subunit give rise to familial pain syndromes called chronic non-paoxysmal neuropathic pain (Catterall et al., 2008; Fischer and Waxman, 2010; Dabby et al. 2011 ). It interacts with the sodium channel beta3 (Scn3b), rather than the beta1 subunit, as well as the collapsing-response mediator protein (Crmp2) through which the analgesic drug lacosamide regulates Nav1.7 current (Kanellopoulos et al. 2018). The R1488 variant is totally inactive (He et al. 2018). Nav1.7 is inhibited by knottins (see TC# 8.B.19.2) (Agwa et al. 2018). Nav1.7 interacts with the following proteins: syn3b (TC# 8.a.17.1.2; the β3 subunit), Crmp2, Syt2 (Q8N9I0) and Tmed10 (P49755), and it also regulates opioid receptor efficacy (Kanellopoulos et al. 2018). Mutations in TRPA1 and Nav1.7 to insensitivity to pain-promoting algogens such as capsaicin, acid, and allyl isothiocyanate (AITC), have been documented (Eigenbrod et al. 2019). Na_v1.7 is associated with endometrial cancer (Liu et al. 2019) and fever-associated seizures or epilepsy (FASE) (Ding et al. 2019). Nav1.7 and Nav1.8 peripheral nerve sodium channels are modulated by protein kinases A and C (Vijayaragavan et al. 2004). Sodium channel Na_V1.7 and potassium channel K_V7.2 promote and oppose excitability in nociceptors, respectively. Inflammation differentially controls transport of depolarizing Nav versus hyperpolarizing Kv channels to drive rat nociceptor activity (Higerd-Rusli et al. 2023). The structural basis for severe pain, caused by mutations in the S4-S5 linkers of voltage-gated sodium channel Na_V1.7, have been revealed (Wisedchaisri et al. 2023).	Eukaryota	Metazoa, Chordata	Nav1.7 of Homo sapiens (Q15858)
1.A.1.10.6	Tetrodotoxin-resistant voltage-gated Na⁺ channel of dorsal ganglion sensory neurons, Na_v1.8, plays a crucial role in the occurrence and development of chronic pain (Akopian et al., 1996) and is essential for pain at low temperatures (Zimmermann et al., 2007). Na_v1.8 is the sole electrical impulse generator in a nociceptor that transmits information to the central nervous system. Bark scorpion venom induces pain in many mammals (house mice, rats, humans) by activating Nav1.7 but has no effect on Nav1.8. Grasshopper mice Nav1.8 has amino acid variants that bind bark scorpion toxins and inhibit Na⁺ currents, blocking action potential propagation and inducing analgesia. These mice thereby can use scorpions as a food source (Zhu et al. 2013; Rowe et al. 2013). Nav1.8 is involved in bull spermatozoa dynamics including motility, membrane integrity, acrosome integrity, capacitation and mitochondrial transmembrane potential (Chauhan et al. 2017). Selective inhibition of Na_V1.8 with VX-548 aleviates acute pain in humans (Jones et al. 2023). N-(((1S,3R,5S)-adamantan-1-yl)methyl)-3-((4-chlorophenyl)sulfonyl)benzenesulfonamide is a novel Nav1.8 inhibitor with an analgesic profile (Song et al. 2024).	Eukaryota	Metazoa, Chordata	Nav1.8 of Rattus norvegicus (Q62968)
1.A.1.10.7	Voltage-sensitive Na⁺ channel, Na_v1.1 or SCN1A (causes epilepsy when mutated) (Rusconi et al., 2007). Mutations are associated with a wide range of mild to severe epileptic syndromes with phenotypes ranging from the relatively mild generalized epilepsy with febrile seizures to other severe epileptic encephalopathies (Colosimo et al. 2007), including myoclonic epilepsy in infancy (SMEI), cryptogenic focal epilepsy (CFE), cryptogenic generalized epilepsy (CGE) and a distinctive subgroup termed as severe infantile multifocal epilepsy (SIMFE) (Ben Mahmoud et al. 2015). Mutations can give rise to familial sporadic hemiplegic migranes (Prontera et al. 2018). An SCN1B variant affects both cardiac-type (NaV1.5) and brain-type (NaV1.1) sodium currents and contributes to complex concomitant brain and cardiac disorders (Martinez-Moreno et al. 2020). Mice null for Scn1b, which encodes NaV beta1 and beta1b subunits, have defects in neuronal development and excitability, spontaneous generalized seizures, cardiac arrhythmias, and early mortality (Martinez-Moreno et al. 2020). The Melkersson-Rosenthal Syndrome and Migraine may be associated with SCN1A variants (Azzarà et al. 2023). A variant in the SCN1A gene confirms Dravet syndrome in a Moroccan child (El Mouhi et al. 2024).	Eukaryota	Metazoa, Chordata	Na_v1.1 of Homo sapiens (P35498)
1.A.1.10.8	The Voltage-gated Na⁺ channel α-subunit, Na_v1.6, encoded by the Scn8a gene which when defective gives rise to the ENU-induced neurological mutant ataxia3 which gives rise to ataxia, tremors, and juvenile lethality. 75% identical to 1.A.1.10.7. Nav1.6 is the dendritic, voltage-gated sodium channel (responsible for dendritic excitability (Lorincz and Nusser, 2010)). Nav1.6 (SCN8A) interacts with microtubule-associated protein (O'Brien et al., 2012). Scorpion alpha toxins bind at receptor site-3 and inhibit channel inactivation, whereas beta toxins bind at receptor site-4 and shift the voltage-dependent activation toward more hyperpolarizing potentials (Gurevitz, 2012). Mutations give rise to epileptic encephalopathy and intellectual disability (O'Brien and Meisler 2013). A gain-of-function mutation gave rise to increased channel activation and infantile epileptic encephalopathy (Estacion et al. 2014). Benign familial infantile seizures (BFIS), paroxysmal kinesigenic dyskinesia (PKD), and their combination - known as infantile convulsions and paroxysmal choreoathetosis (ICCA) - are related autosomal dominant diseases involving SCN8A (Gardella et al. 2015). Mutations can lead to chronic movement disorder in the mouse (Jones et al. 2016), and loss of function mutations in humans can lead to intellectual disability without seizures (Wagnon et al. 2017). Nav1.6 has been quantitated in mouse brain and proved to be present in 2-fold decreased amounts in epileptic mice (Sojo et al. 2019). SCN8A developmental and epileptic encephalopathy results in intractable seizures including spasms, focal seizures, neonatal status epilepticus, and nonconvulsive status epilepticus (Kim et al. 2019). Mutations in the SCN8A gene causes early infantile epileptic encephalopathy (Pan and Cummins 2020). Amitriptyline is a tricyclic antidepressant that binds to the anesthetic binding site in the α-subunit of the channel protein (Wang et al. 2004). A heterobivalent ligand (mu-conotoxin KIIIA, which occludes the pore of the NaV channels, and an analogue of huwentoxin-IV, a spider-venom peptide that allosterically modulates channel gating (TC#8.B.3.1.3)) slows ligand dissociation and enhances potency (Peschel et al. 2020). Several FDA‑approved drugs that are highly correlated with Nav1.6 could be candidate drugs for patients with glioma (Ai et al. 2023). Clinical and electrophysiological features of SCN8A variants cause episodic or chronic ataxia (Lyu et al. 2023). Epilepsy can be due to variants of the SCN8A gene (Zhang et al. 2024).	Eukaryota	Metazoa, Chordata	Na_v1.6 of Homo sapiens (Q9UQD0)
1.A.1.10.9	The voltage-gated Na⁺ channel α-subunit, Na_v1.9. It is present in excitable membranes and is resistant to tetrodotoxin and saxitoxin (Bosmans et al., 2011). The mutation, S360Y, makes NaV1.9 channels sensitive to tetrodotoxin and saxitoxin, and the unusual slow open-state inactivation of Na_V1.9 is mediated by the isoleucine-phenylalanine-methionine inactivation motif located in the linker connecting domains III and IV (Goral et al. 2015). Gain-of function mutations can lead to heritable pain disorders, and painful small-fibre neuropathy (Han et al. 2016). It is a threshold channel that regulates action potential firing, and is preferentially expressed in myenteric neurons, the small-diameter dorsal root ganglion (DRG) and trigeminal ganglion neurons including nociceptors. There is a monogenic Mendelian link of Nav1.9 to human pain disorders including episodic pain due to a N816K mutation (Huang et al. 2019). The human neuronal sodium channel Nav1.9 is inhibitied by ACEA (arachidonyl-2-chloroethylamide), an analogue of anandamide (Marchese-Rojas et al. 2022). .	Eukaryota	Metazoa, Chordata	Na_v1.9 of Homo sapiens (Q9UI33)
1.A.1.10.10	The insect (cockroach) Na⁺channel. Batrachotoxin, pyrethroids, and BTG 502 share overlapping binding sites (Du et al., 2011). Insecticides tagetting Na⁺ channels include indoxacarb and metaflumizone (Casida and Durkin 2013). They preferably bind to and trap sodium channels in the slow-inactivated non-conducting state, a mode of action similar to that of local anesthetics (Jiang et al. 2015). Asp802 is involved in gating and action, but not binding, of pyrethroid insecticides (Du et al. 2010).	Eukaryota	Metazoa, Arthropoda	Na⁺ channel of Blattella germanica (O01307)
1.A.1.10.11	Sodium channel of 2215 aas and 24 TMSs, VmNa. An L925V mutation in the channel domain renders the honey bee mites resistant to pyrethroids such as tau- fluvalinate and flumethrin (González-Cabrera et al. 2013).	Eukaryota	Metazoa, Arthropoda	VmNa of Varroa destructor
1.A.1.10.12	Type 2 Na⁺ channel, SCN2A or NaV1.2, of 2,005 aas and 24 TMSs. Mutations give rise to epileptic encephalophathy, Ohtahara syndrome (Nakamura et al. 2013). They may also give rise to autism (ASD) (Tavassoli et al. 2014). This protein is orthologous to the rat Na⁺ channel, TC# 1.A.1.10.1 and very similar to the type 1 Na⁺ channel (1.A.1.10.7). Na_V1.2 has a single pore-forming alpha-subunit and two transmembrane beta-subunits. Expressed primarily in the brain, Na_V1.2 is critical for initiation and propagation of action potentials. Milliseconds after the pore opens, sodium influx is terminated by inactivation processes mediated by regulatory proteins including calmodulin (CaM). Both calcium-free (apo) CaM and calcium-saturated CaM bind tightly to an IQ motif in the C-terminal tail of the alpha-subunit. Thermodynamic studies and solution structure (2KXW) of a C-domain fragment of apo 13C,15N- CaM (CaMC) bound to an unlabeled peptide with the sequence of the rat NaV1.2 IQ motif showed that apo CaMC (a) was necessary and sufficient for binding, and (b) bound more favorably than calcium-saturated CaMC. CaMN apparently does not influence apo CaM binding to NaV1.2IQp (Mahling et al. 2017). The phenotypic spectrum of SCN2A-related epilepsy is broad, ranging from benign epilepsy in neonate and infancy to severe epileptic encephalopathy. Oxcarbazepine and valproate are the most effective drugs in epilepsy patients with SCN2A variants. Sodium channel blockers often worsen seizures in patients with seizure onset beyond 1 year of age. Abnormal brain MRI findings and de novo variations are often related to poor prognosis. Most SCN2A variants located in transmembrane regions were related to patients with developmental delay (Zeng et al. 2022). The beta4-subunit and PRRT2 form a push-pull system that finely tunes the membrane expression and function of Na_V channels and the intrinsic neuronal excitability (Valente et al. 2022). Icariin can be used to treat epilepsy by inhibiting neuroinflammation via promoting microglial polarization to the M2 phenotype (Wang et al. 2023).	Eukaryota	Metazoa, Chordata	SCN2A of Homo sapiens
1.A.1.10.13	Voltage-sensitive Na⁺channel of 2821 or 2844 aas (see Uniprot Q9W0Y8) aas and 24 TMSs (Cohen et al. 2009). Pyrethroid, an insecticide, binds to insect Na⁺ channels at two sites called pyrethroid,receptors, PyR1 (initial) and PyR2, located in the domain interfaces II/III and I/II, respectively, and binding residues have been identified (Du et al. 2015). It's homologue in honeybees, CaV4, has distinct permeation, inactivation, and pharmacology from homologous NaV channels (Bertaud et al. 2024). Specifically, honeybee Ca_V4 has distinct permeation, being specific for Ca²⁺, and exhibits inactivation, and pharmacology differing from homologous Na_V channels (Bertaud et al. 2024).	Eukaryota	Metazoa, Arthropoda	Na⁺ channel of Drosophila melanogaster
1.A.1.10.14	The voltage-gated Ca²⁺ channel (VDCC; CAV2), α-subunit of 2027 aas and 24 TMSs in four domains, each with six transmembrane segments and EEEE loci in the ion-selective filter, typical of VDCCs in vertebrates. CAV2 primarily localizes in the distal part of flagella and is transported toward the flagellar tip via intraflagellar transport (IFT) although CAV2 accumulates near the flagellar base when IFT is blocked. Thus, Ca²⁺ influx into Chlamydomonas flagella is mediated by the VDCC, CAV2, whose distribution is biased to the distal region of the flagellum, and this is required for flagellar waveform conversion (Fujiu et al. 2009).	Eukaryota	Viridiplantae, Chlorophyta	CAV2 of Chlamydomonas reinhardtii (Chlamydomonas smithii)
1.A.1.10.15	The sodium channel of 1989 aas and 24 TMSs. 80% identical to the characterized channel of the crayfish (Astacus leptodactylus (Turkish narrow-clawed crayfish) (Pontastacus leptodactylus)) in which functional regions responsible for the selectivity filter, inactivation gate, voltage sensor, and phosphorylation have been identified (Coskun and Purali 2016).		Metazoa, Arthropoda	Na⁺ channel of Cancer borealis (Jonah crab)
1.A.1.10.16	The voltage-gated sodium channel of 2147 aas and 24 TMSs. Several mutations in the structural gene give rise to pyrethroid resistance (kdr) (Saavedra-Rodriguez et al. 2007). A novel strategy for screening mutations in the voltage-gated sodium channel gene of Aedes albopictus based on multiplex PCR-mass spectrometry minisequencing technology, has appeared (Mu et al. 2023).	Eukaryota	Metazoa, Arthropoda	Na⁺ channel of Aedes aegypti (Yellowfever mosquito) (Culex aegypti), the most prevalent vector of dengue and yellow fever viruses.
1.A.1.10.17	Voltage-gated Na⁺ Channel protein of 2,139 aas and 24 TMSs. Mediates voltage-dependent sodium ion permeability of excitable membranes. 3-d modeling revealed spacial clustering of evolutionarily conserved acidic residues at extracellular sites (Vinekar and Sowdhamini 2016).	Eukaryota	Metazoa, Arthropoda	PARA sodium channel of Anopheles gambiae (African malaria mosquito)
1.A.1.10.18	Sodium channel protein, α-subunit, FPC1, of 2050 aas and 24 TMSs. The 3-d structure has been solved by cryoEM to 3.8 Å resolution (Shen et al. 2017). One residue at the corresponding selectivity filter (SF) locus in each repeat, Asp/Glu/Lys/Ala (DEKA), determines Na⁺ selectivity. The S1 to S4 segments in each repeat form a voltage-sensing domain (VSD), wherein S4 carries repetitively occurring positive residues essential for voltage sensing. There are seven extracellular glycosylation sites (Shen et al. 2017).	Eukaryota	Metazoa, Arthropoda	FPC1 of Periplaneta americana (American cockroach) (Blatta americana)
1.A.1.10.19	Sodium channel Nav1.4-beta complex of 1820 and 209 aas, respectively. Voltage-gated sodium (Nav) channels initiate and propagate action potentials. Yan et al. 2017 presented the cryo-EM structure of EeNav1.4, the Nav channel from electric eel, in complex with the beta1 subunit at 4.0 Å resolution. The immunoglobulin domain of beta1 docks onto the extracellular L5I and L6IV loops of EeNav1.4 via extensive polar interactions, and the single transmembrane helix interacts with the third voltage-sensing domain (VSDIII). The VSDs exhibit "up" conformations, while the intracellular gate of the pore domain is kept open by a digitonin-like molecule. Structural comparison with closed NavPaS shows that the outward transfer of gating charges is coupled to the iris-like pore domain dilation through intricate force transmissions involving multiple channel segments. The IFM fast inactivation motif on the III-IV linker is plugged into the corner enclosed by the outer S4-S5 and inner S6 segments in repeats III and IV, suggesting a potential allosteric blocking mechanism for fast inactivation (Yan et al. 2017). The PDB# for the complex is 5XSY, and that for the two subunits are 5XSY_A and 5XSY_B. Domain 4 TMS 6 of Nav1.4 plays a key role in channel gating regulation, and is targeted by the neurotoxin, veratridine (VTD) (Niitsu et al. 2018).	Eukaryota	Metazoa, Chordata	Nav1.4-beta subunits of Electrophorus electricus (Electric eel) (Gymnotus electricus)
1.A.1.10.20	Voltage-gated sodium channel of 1836 aas and 24 TMSs, PaFPC1. The 3-d structure has been determined (Shen et al. 2017). It mediates the voltage-dependent sodium ion permeability in excitable membranes.	Eukaryota	Metazoa, Arthropoda	PaFPC1 of Periplaneta americana (American cockroach) (Blatta americana)
1.A.1.10.21	Putative two component voltage-gated Na⁺ channel, subunit 1 of 1149 aas and subunit 2 of 958 aas. Decreased expression of these genes, encoding this system, gives rise to mortality of the peach-potato aphid, Myzus persicae (Tariq et al.* 2019).*	Eukaryota	Metazoa, Arthropoda	NaV of Myzus persicae.
1.A.1.10.22	The Na⁺-activated Na⁺ channel (Nax; also called SCN7A; of 1737 aas and ~24 TMSs) and salt-inducible kinase (SIK, see TC# 8.A.104.1.14) are stimulated by increases in local Na⁺ concentration, affecting the Na⁺,K⁺-ATPase activity (see TC# 3.A.3.1.1). It mediates the voltage-dependent sodium ion permeability of excitable membranes. Assuming opened or closed conformations in response to the voltage difference across the membrane, the protein forms a sodium-selective channel through which Na⁺ ions may pass in accordance with their electrochemical gradient (Gonsalez et al. 2023). Rare SCG genetic variants may contribute to the development of painful neuropathy (Almomani et al. 2023).	Eukaryota	Metazoa, Chordata	Nax of Homo sapiens
1.A.1.11.1	Voltage-sensitive Ca²⁺ channel (transports Ca²⁺, Ba²⁺ and Sr²⁺)	Eukaryota	Metazoa, Chordata	Voltage-sensitive Ca²⁺ channel, α-1 chain of Rattus norvegicus
1.A.1.11.2	Muscle plasmalemma, voltage-gated, L-type dihydropyridine receptor Ca²⁺ channel, α-1 subunit (DHPR) (Ba²⁺ > Ca²⁺), Cav1.1, CACNA1S,CACH1 CDCN1, CACNL1A3 of 1873 aas in the human orthologue. Distinc voltage sensor domains control voltage sensitivity and kinetics of current activation (Tuluc et al. 2016). Rapid changes in the transmembrane potential are detected by the voltage-gated Ca²⁺ channel, dihydropyridine receptor (DHPR), embedded in the sarcolemma. DHPR transmits the contractile signal to another Ca²⁺ channel, the ryanodine receptor (RyR1), embedded in the membrane of the sarcoplasmic reticulum (SR), which releases a large amounts of Ca²⁺ from the SR that initiate muscle contraction (Shishmarev 2020).	Eukaryota	Metazoa, Chordata	DHPR of Oryctolagus cuniculus
1.A.1.11.3	Voltage-dependent R-type Ca²⁺ channel, α-1E subunit (Cav2.3) (brain Ca²⁺ channel type II) (Ca²⁺ > Ba²⁺). Interacts with V-type ATPases (3.A.2), specifically, the G1-subunit, to regulate its activity (Radhakrishnan et al., 2011). Syntaxin-3 (Syn-3) interacts directly with Cav2.3 to regulate its activity (Xie et al. 2016). A Ca_v3.2 calcium channel missense variant is associated with epilepsy and hearing loss (Stringer et al. 2023). Structural insights into the allosteric effects of the antiepileptic drug topiramate on the Ca_V2.3 channel have been published (Gao et al. 2024).	Eukaryota	Metazoa, Chordata	R-type Ca²⁺ channel of Mus musculus
1.A.1.11.4	The voltage-dependent L-type Ca²⁺ channel α-subunit-1C (L-type Ca_v1.2), CACNA1C (CACH2, CACN2, CACNL1A1, CCHL1A1) of 2221 aa. Mutations cause Timothy's syndrome, a disorder associated with autism (Splawski et al., 2006). The C-terminus of Ca_v1.2 encodes a transcription factor (Gomez-Ospina et al., 2006). Ca_v1.2 associates with the α-2, δ-1, β and γ subunits (Yang et al., 2011). The CRAC channel activator STIM1 binds and inhibits L-type voltage-gated calcium channel, Ca_v1.2 (Park et al., 2010). This channel appears to function as the molecular switch for synaptic transmission (Atlas 2013). Intramembrane signalling occurs with syntaxin 1A for catecholamine release in chromaffin cells (Bachnoff et al. 2013). miR-153 intron RNA is a negative regulator of both insulin and dopamine secretion through its effect on Cacna1c expression, suggesting that IA-2beta and miR-153 have opposite functional effects on the secretory pathway (Xu et al. 2015). Co-localizes with Syntaxin-1A in nano clusters at the plasma membrane (Sajman et al. 2017). It is a high voltage-activated Ca²⁺ channel in contrast to Ca_v3.3 which is a low voltage-activated Ca²⁺ channel (Sanchez-Sandoval et al. 2018). Nifedipine blocks and potentiates this and other L-type VIC Ca²⁺ channels (Wang et al. 2018). Cav1.2 is upregulated when STIM1 is deficient (Pascual-Caro et al. 2018). CaV1.2 regulates chondrogenesis during limb development (Atsuta et al. 2019). CACNA1C may be a prognostic predictor of survival in ovarian cancer (Chang and Dong 2021). Kinase and phosphatase modulation of T-type Ca²⁺ channel (TTCC) isoforms Cav3.1, Cav3.2, and Cav3.3, are mostly described for roles unrelated to cellular excitability (Sharma et al. 2023), and potential modulations that are yet to be explored are also discussed. Palmitoylation of the pore-forming subunit of Ca(v)1.2 controls channel voltage sensitivity and calcium transients in cardiac myocytes (Kuo et al. 2023). A novel binding site between the voltage-dependent calcium channel Ca_V1.2 subunit and the Ca_Vβ2 subunit has been discovered using a new analysis method for protein-protein interactions (Murakami et al. 2023). CACNA1C is one of the top risk genes for schizophrenia; A novel 17-variant block across introns 36-45 of CACNA1C was significantly associated with schizophrenia; a novel 17-variant block across introns 36-45 of CACNA1C was responsible (Guo et al. 2023). A novel binding site has been found between the voltage-dependent calcium channel Ca_V1.2 subunit and Ca_Vβ2 subunit (Murakami et al. 2023). The Ca_V1.2 distal carboxy terminus functions in the regulation of L-type current (Arancibia et al. 2024).	Eukaryota	Metazoa, Chordata	CACNA1C of Homo sapiens (2221 aas; Q13936)
1.A.1.11.5	The voltage-dependent L-type Ca²⁺ channel α-subunit-1H (T-type Ca_v3.2), CACNA1H (mutations can cause an increased propensity for autism spectrum disorders (ASD) characterized by impaired social interactions, communication skills and restricted and repetitive behaviors) (Splawski et al., 2006). Also called Cav3.2 or VSCC. Involved in a variety of calcium-dependent processes, including muscle contraction, hormone or neurotransmitter release, gene expression, cell motility, cell division and cell death. The isoform alpha-1H gives rise to T-type calcium currents, ''low-voltage activated'' currents blocked by nickel and mibefradil. Defective in Childhood Absence Epilepsy. Are permeated by divalent metal ions, such as Fe²⁺ and Mn²⁺, and possibly Cd²⁺ (Thévenod, 2010). Patented inhibitors of T-type calcium channels have been reviewed (Giordanetto et al. 2011). Regulated by Syntaxin-1A (Xie et al. 2016). T-type calcium channel blockade induces apoptosis in C2C12 myotubes and skeletal muscle via endoplasmic reticulum stress activation (Chen et al. 2020). Gabapentin disrupts binding of perlecan to the α₂δ₁ voltage-sensitive calcium channel subunit and impairs skeletal mechanosensation (Reyes Fernandez et al. 2022). Kinase and phosphatase modulation of T-type Ca²⁺ channel (TTCC) isoforms Cav3.1, Cav3.2, and Cav3.3, are mostly described for roles unrelated to cellular excitability (Sharma et al. 2023), and potential modulations that are yet to be explored are also discussed. A subtle role for T-type calcium channels in regulating lymphatic contraction has been established (Davis et al. 2023). A Ca_v3.2 calcium channel missense variant is associated with epilepsy and hearing loss (Stringer et al. 2023).	Eukaryota	Metazoa, Chordata	CACNA1H of Homo sapiens (2353 aas; Q95180)
1.A.1.11.6	Voltage-dependent L-type Ca²⁺ channel subunit α-1C (αCa_v1.2) of cardiac muscle [A C-terminal fragment of Ca_v1.2 translocates to the nucleus and regulates transcription, explaining how a channel can directly activate transcription and differentiation of excitable cells.] (Gomez-Ospina et al., 2006). Ca_v1.2 associates with the α-2, δ-1, β and γ subunits (Yang et al., 2011). Voltage-gated Ca²⁺ influx and mitochondrial Ca²⁺ initiate secretion from Aplysia neuroendocrine cells (Hickey et al. 2013).	Eukaryota	Metazoa, Chordata	α-Ca_v1.2 of Mus musculus (2139 aas; Q01815)
1.A.1.11.7	The voltage-dependent Ca²⁺ channel subunit α-1I, Cav3.3, CACNA1I (isoform CRA_c (2223 aas and 24 TMSs)) (Hamid et al. 2006). It is a low voltage-activated Ca²⁺ channel in contrast to Ca_v1.2 (TC# 1.A.1.11.4) which is a high voltage-activated Ca²⁺ channel (Sanchez-Sandoval et al. 2018). The homolog in Cynops pyrrhogaster (85% identical) is inhibited by Ni²⁺ and may play a role in the sperm acrosome reaction (Kon et al. 2019). Kinase and phosphatase modulation of T-type Ca²⁺ channel (TTCC) isoforms Cav3.1, Cav3.2, and Cav3.3, are mostly described for roles unrelated to cellular excitability (Sharma et al. 2023), and potential modulations that are yet to be explored are also discussed. A possible involvement of CaV3 in carcinogenic processes and is a potential pharmacological target in new therapies for breast cancer treatment (Aguiar et al. 2023). G protein β subunits regulate Ca_v3.3 T-type channel activity and current kinetics via interaction with the Ca_v3.3 C-terminus (Jeong et al. 2024).	Eukaryota	Metazoa, Chordata	Ca²⁺ channel CRA_c of Homo sapiens (Q9P0X4)
1.A.1.11.8	Voltage-dependent Ca²⁺ channel α-1A subunit (2212 aas), Cav2.1 (P/Q-type) (when mutated in humans, leads to a human channelopathy (episodic ataxia type-2 (EA2)) due to protein misfolding and retention in the E.R. (Mezghrani et al., 2008; Kleopa, 2011). Mutations give rise to familial and sporadic hemiplegic migraine type 1 (FHM1, SHM1), episodic ataxia type 2 (EA2), and spinocerebellar ataxia type 6 (SCA6) (García Segarra et al. 2014). Syntaxin 1A (Sx1A), SNAP-25 and synaptotagmin (Syt1), either alone or in combination, modify the kinetic properties of voltage-gated Ca²⁺ channels (VGCCs) including Cav2.1 (Cohen-Kutner et al. 2010).	Eukaryota	Metazoa, Chordata	Cav2.1 of Rattus norvegicus (P54282)
1.A.1.11.9	Voltage-dependent Ca²⁺ channel -subunit 1B (2339 aas), Cav2.2 (N-type) or NCC receptor of 2237 aas. Anchorin B interacts with Cav2.2 in the loop between TMSs 2 and 3. TSPAN-13 specifically interacts with the α-subunit and modulates the efficiency of coupling between voltage sensor activation and pore opening of the channel while accelerating the voltage-dependent activation and inactivation of the Ba²⁺ current through CaV2.2 (Mallmann et al. 2013). The structure of the closed state in the pore forming domains have been modeled (Pandey et al. 2012). Amlodipine, cilnidipine and nifedipine compounds are potent channel antagonists. Ca_V2.2 also interacts with reticulon 1 (RTN1) (TC# 8.A.102), member 1 of solute carrier family 38 (SLC38, TC#2.A.18), prostaglandin D2 synthase (PTGDS) and transmembrane protein 223 (TMEM223; TC#8.A.115). Of these, TMEM223 and, to a lesser extent, PTGDS, negatively modulate Ca²⁺ entry, required for transmitter release and/or for dendritic plasticity under physiological conditions (Mallmann et al. 2019). Phillygenin suppresses glutamate exocytosis in rat cerebrocortical nerve terminals (synaptosomes) through the inhibition of Ca_v2.2 calcium channels (Lee et al. 2024).	Eukaryota	Metazoa, Chordata	Cav2.2 of Mus musculus (O55017)
1.A.1.11.10	Plasma membrane voltage-gated, high affinity Ca²⁺ channel, Cch1/Mid1; activated by mating pheromones and environmental stresses; required for growth in low Ca²⁺ (Locke et al., 2000; Paidhungat and Garrett, 1997). Also essential for tolerance to cold stress and iron toxicity (Peiter et al., 2005). Ecm7, (448aas; 4 TMS; TC# 1.H.1.4.6), a member of the PMP-22/EMP/MP20 Claudin superfamily of transmembrane proteins that includes gamma-subunits of voltage-gated calcium channels appears to interact with Mid1 TC# 8.A.41.1.1) and regulate the activity of the Cch1/Mid1 channel (Martin et al., 2011). Ecm7p is related to members of TC families 1.H.1, 1.H.2 and 1.A.81. The two indispensable subunits, Cch1 and Mid1 are equivalent to the mammalian pore-forming α₁ and auxiliary α₂ /δ subunits, respectively. Cho et al. 2016 screened candidate proteins that interact with Mid1 and identified the plasma membrane H⁺-ATPase, Pma1 (TC#3.A.3.3.6). Mid1 co-immunoprecipitated with Pma1. At the nonpermiss, and Mid1-EGFP colocalized with Pma1-mCherry at the plasma membrane. Using a temperature-sensitive mutant, pma1-10, the membrane potential was less negative, and Ca²⁺ uptake was lower than in wild-type cells. Thus, Pma1 interacts physically with Cch1/Mid1 Ca²⁺ channels to enhance their activity via its H⁺-pumping activity (Cho et al. 2016).	Eukaryota	Fungi, Ascomycota	Cch1/Mid1 of Saccharomyces cerevisiae Cch1 (P50077) Mid1 (P41821) Ecm7p (Q06200)
1.A.1.11.11	The Ca_v1.4 L-type Ca²⁺ channel (gene CACNA1F). Mutations resulting in increased activity cause x-linked incomplete congenital stationary night blindness (CSNB2) (Hemara-Wahanui et al., 2005; Peloquin et al., 2007). Aland Island eye disease (AIED), also known as Forsius-Eriksson syndrome, is an X-linked recessive retinal disease characterized by a combination of fundus hypopigmentation, decreased visual acuity, nystagmus, astigmatism, protan color vision defect, progressive myopia, and defective dark adaptation. Since the clinical picture of AIED is quite similar to CSNB2, these disorders are allelic or form a single entity. Thus, AIED is also caused by CACNA1F gene mutations (Jalkanen et al. 2007). Ca_v1.4 calcium channels play roles in the pathophysiology of psoriasis (Pelletier and Savignac 2022). Cav1.4 L-type calcium channels are predominantly expressed at the photoreceptor terminals and in bipolar cells, mediating neurotransmitter release. Mutations in its gene, CACNA1F, can cause congenital stationary night-blindness type 2 (CSNB2). Water wires in both, resting and active channel states have been proposed (Heigl et al. 2023).	Eukaryota	Metazoa, Chordata	Ca_v1.4 of Homo sapiens (O60840)
1.A.1.11.12	T-type Ca²⁺ channel (CACNA1G; Ca_v3.1d), (σ1G T-type Ca²⁺ channel) in developing heart (fetal myocardium (Cribbs et al., 2001)) and elsewhere. Both Ca_v3.1 and Ca_v3.2 are permeated by divalent metal ions, such as Fe²⁺ and Mn²⁺, and possibly Cd²⁺ (Thévenod, 2010). Ca_V3.1 channels are activated at low votage and regulate neuronal excitability in the spinal cord (Canto-Bustos et al. 2014). It is regulated by protein kinase C (PKC) and the RanBPM protein (Q96S59) (Kim et al. 2009). T-type calcium channels belong to the "low-voltage activated (LVA)" group and are strongly blocked by mibefradil. A particularity of this type of channel is an opening at quite negative potentials and voltage-dependent inactivation. T-type channels serve pacemaking functions in both central neurons and cardiac nodal cells, and support calcium signaling in secretory cells and vascular smooth muscle (Coutelier et al. 2015). The human ortholog is 85% identical to the mouse protein. These channels also determines the angiogenic potential of pulmonary microvascular endothelial cells (Zheng et al. 2019).	Eukaryota	Metazoa, Chordata	Ca_v3.1d of Mus musculus (Q9WUT2)
1.A.1.11.13	Two-pore Ca²⁺ channel protein 1, TPC1 (K_m(Ca²⁺))=50 µM; voltage gated; 461 aas; 12 TMSs) (Hashimoto et al., 2004; Kurusu et al, 2004; 2005). Each TPC subunit contains 12 TMSs that can be divided into two homologous copies of an S1-S6 Shaker-like 6-TMS domain. A functional TPC channel assembles as a dimer. The plant TPC channel is localized in the vacuolar membrane and is also called the SV channel for generating the slow vacuolar (SV) current. Three subfamilies of mammalian TPC channels have been defined - TPC1, 2, and 3 - with the first two being ubiquitously expressed in animals and TPC3 being expressed in some animals, but not in humans. Mammalian TPC1 and TPC2 are localized to endolysosomal membranes (She et al. 2022).	Eukaryota	Viridiplantae, Streptophyta	TPC1 of Oryza sativa (Q5QM84)
1.A.1.11.14	Voltage-dependent calcium channel, α-1 subunit (1911aas), CyCaα1	Eukaryota	Metazoa, Cnidaria	CyCaα1 of Cyanea capillata (O02038)
1.A.1.11.15	Neuronal nonselective cation channel, NALCN (forms background leak conductance and controls neuronal excitability; Lu et al., 2007). It is also found in the pancreatic β-cell (Swayne et al. 2010). NALCN serves as a variable sensor that responds to calcium or sodium ion flux, depending on whether the total cellular current density is generated more from calcium-selective or sodium-selective channels (Senatore and Spafford 2013). It functions in a complex with Unc80 (3258 aas; Q8N2C7) and Unc79 (2635 aas; Q9P2D8) (Bramswig et al. 2018). Heterozygous de novo NALCN missense variants in the S5/S6 pore-forming segments lead to congenital contractures of the limbs and face, hypotonia, and developmental delay (Bramswig et al. 2018). Overexpression of the NALCN gene ablates allyl isothiocyanate-promoting pain reception by nociceptors (Eigenbrod et al. 2019).	Eukaryota	Metazoa, Chordata	NALCN of Homo sapiens (Q6P2S6)
1.A.1.11.16	4 domain-type voltage-gated ion channel, α-1 subunit NCA-2 (Jospin et al., 2007) (dependent on Unc-80 (3225aas; CAB042172) for proper localization).	Eukaryota	Metazoa, Nematoda	NCA-2 of Caenorhabditis elegans (Q06AY4)
1.A.1.11.17	The high affinity Ca²⁺ channel; associates with elongation factor 3 (EF3) to target Cch1/Mid1 to the plasma membrane (Liu and Gelli, 2008).	Eukaryota	Fungi, Basidiomycota	Cch1/Mid1 of Cryptococcus neoformans Cch1 (Q1HHN2) Mid1 (Q5KM96)
1.A.1.11.18	The nicotinic acid adenine dinucleotide phosphate (NAADP)- dependent two pore Ca²⁺- channel, TPC3 (Brailoiu et al., 2010). Phosphoinositides regulate dynamic movement of the S4 voltage sensor in the second repeat in two-pore channel 3 (Hirazawa et al. 2021). Each TPC subunit contains 12 TMSs that can be divided into two homologous copies of an S1-S6 Shaker-like 6-TMS domain. A functional TPC channel assembles as a dimer. The plant TPC channel is localized in the vacuolar membrane and is also called the SV channel for generating the slow vacuolar (SV) current. Three subfamilies of mammalian TPC channels have been defined - TPC1, 2, and 3 - with the first two being ubiquitously expressed in animals and TPC3 being expressed in some animals, but not in humans. Mammalian TPC1 and TPC2 are localized to endolysosomal membranes (She et al. 2022).	Eukaryota	Metazoa, Chordata	Two pore Ca²⁺ channel 3, TPC3 of Bos taurus (C4IXV8)
1.A.1.11.19	The phosphoinositide (PI(3,5)P₂)-activated Na⁺two porechannel-2, TPC2, in endosomes and lysosomes (Wang et al. 2012). Previously thought, incorectly, according to Wang et al. 2012, to be a nicotinic acid adenine dinucleotide phosphate (NAADP)-dependent two pore Ca²⁺channel. TPC2, like TPC1, has a 12 TMS topology (two channel units) (Hooper et al., 2011). The two domains of human TPCs can insert into the membrane independently (Churamani et al., 2012). Cang et al. (2013), showed that TPC1 and TPC2 together form an ATP-sensitive two-pore Na⁺ channel that senses the metabolic state of the cell. The channel complex detects nutrient status, becomes constitutively open upon nutrient removal, and controls the lysosome's membrane potential, pH stability, and amino acid homeostasis. Essential for Ebola virus (EBOV) host entry. Several inhibitors of TPC2 that act in the nM (tetrandrine) or μM (verapamil; Ned19) range block channel activity, prevent Ebola Virus from escaping cell vesicles and may be used to treat the disease (Sakurai et al. 2015). TPC2 may transport both Na⁺ and Ca²⁺ (Sakurai et al. 2015). Lipid-gated monovalent ion fluxes, mediated by TPC1 and TPC2 in mice, regulate endocytic traffic and support immune surveillance. This is in part achieved by catalyzing Na⁺ export from visicles derived from the plasma membrane by phagocytosis or pinocytosis, causing contraction and allowing the maintenance of a uniform cell volume (Freeman et al. 2020). This system is important for melanocyte function (Wiriyasermkul et al. 2020). Convergent activation of two-pore channels mediated by the NAADP-binding proteins JPT2 and LSM12 has been reported (Gunaratne et al. 2023). The lysosomal two-pore channels 2 (TPC2) and IP3 receptors (IP3Rs) located in the endoplasmic reticulum may be coupled (Yuan et al. 2024).	Eukaryota	Metazoa, Chordata	TPC2 of Homo sapiens (Q8NHX9)
1.A.1.11.20	The voltage-gated Ca²⁺ channel, L-type α-subunit, Eg1-19 regulated by Macoilin (8.A.38.1.2)	Eukaryota	Metazoa, Nematoda	Eg1-19 of Caenorhabditis elegans (A8PYS5)
1.A.1.11.21	Voltage-gated L-type Ca²⁺ channel, Egl-19, isoform a. There are three isoforms encoded by the same gene, isoforms a, b and c, and all are expressed in all types of muscle (McDonald et al. 2023).	Eukaryota	Metazoa, Nematoda	Egl-19 of C. elegans (G5EG02)
1.A.1.11.22	The phosphoinositide (PI(3,5)P₂)-activated Na⁺two porechannel-1, TPC1 of endosomes and lysosomes (Wang et al. 2012). Previously thought, incorectly, according to Wang et al. (2012), to be an NAADP-activated two pore voltage-dependent calcium channel protein. However, Cang et al. (2013), showed that TPC1 and TPC2 (TC# 1.A.1.11.19) together form an ATP-sensitive two-pore Na⁺ channel that senses the metabolic state of the cell. The channel complex detects nutrient status, becomes constitutively open upon nutrient removal, and controls the lysosome's membrane potential, pH stability, and amino acid homeostasis. May be regulated by the HCLS-associated X-1 (HAX-1) protein (Lam et al. 2013). The cryoEM 3-D structure has been ellucidated (She et al. 2018). This voltage-dependent, phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P₂)-activated Na⁺ channel was solved in both the apo closed state and ligand-bound open state. The channel has a coin-slot-shaped ion pathway in the filter that defines the selectivity of mammalian TPCs. Only the voltage-sensing domain from the second 6-TMS domain confers voltage dependence while endolysosome-specific PtdIns(3,5)P₂ binds to the first 6-TMS domain and activates the channel under conditions of depolarizing membrane potential. Structural comparisons between the apo and PtdIns(3,5)P2-bound structures show the interplay between voltage and ligand activation. These MmTPC1 structures reveal lipid binding and regulation in a 6-TMS voltage-gated channel (She et al. 2018).	Eukaryota	Metazoa, Chordata	Tpcn1 of Mus musculus
1.A.1.11.23	Cch1 calcium channel, alpha subunit; acts with Mid1 (8.A.41.1.7) which is required for function.	Eukaryota	Fungi, Ascomycota	Mid1 of Schizosaccharomyces pombe
1.A.1.11.24	Voltage-sensitive calcium channel of 2693 aas (Docampo et al. 2013). Found to be essential for bloodstream-form Trypanosoma brucei through a genome-wide RNAi screen (Schmidt et al. 2018).	Eukaryota	Kinetoplastida	Calcium channel of Trypanosoma brucei
1.A.1.11.25	Endosomal/lysosomal, two pore Na⁺and Ca²⁺-release channel (Na⁺> Ca²⁺) protein of 816 aas and 12 TMSs, TPC1 or TPCN1 (Guo et al. 2017). Endosomes and lysosomes are electrically excitable organelles (Cang et al. 2014). In a subpopulation of endolysosomes, a brief electrical stimulus elicits a prolonged membrane potential depolarization spike. The organelles have a depolarization-activated, non-inactivating Na⁺ channel (lysoNaV). The channel is formed by a two-repeat six-transmembrane-spanning (2x6 TMS) protein, TPC1, which represents the evolutionary transition between 6 TMS and 4x6 TMS voltage-gated channels. Luminal alkalization also opens lysoNaV by markedly shifting the channel's voltage dependence of activation toward hyperpolarization. Thus, TPC1 is a voltage-gated Na⁺ channel that senses pH changes and confers electrical excitability to organelles (Cang et al. 2014). Essential for Ebola virus (EBOV) host entry. Several inhibitors act in the nM (tetrandrine) or μM (verapamil; Ned19) range to block Na⁺ and Ca²⁺ channel activity, inhibit virus escape from membrane vesicles and may possibly be used to treat the disease (Sakurai et al. 2015). A cluster of arginine residues in the first domain required for selective voltage-gating of TPC1 map not to the voltage-sensing fourth transmembrane region (S4) but to a cytosolic downstream region (S4-S5 linker). These residues are conserved between TPC isoforms suggesting a generic role in TPC activation. Accordingly, mutation of residues in TPC1 but not the analogous region in the second domain prevents Ca²⁺ release by NAADP in intact cells (Patel et al. 2017). Dramatic conformational changes in the cytoplasmic domains communicate directly with the VSD during activation (Kintzer et al. 2018). PGRMC1 (the progesterone receptor membrane component1), an ER transmembrane protein that undergoes a unique heme-dependent dimerization, is an interactor of the endosomal two pore channel, TPC1. It regulates ER-endosomal coupling with functional implications for cellular Ca²⁺ dynamics (Gunaratne et al. 2023). Convergent activation of two-pore channels mediated by the NAADP-binding proteins JPT2 and LSM12 has been reported (Gunaratne et al. 2023).	Eukaryota	Metazoa, Chordata	TPC1 of Homo sapiens
1.A.1.11.26	Two pore Ca²⁺> Na⁺, Li⁺ or K⁺ (non-selective for these three monovalen caions) channel protein of 733 aas and 12 TMSs, TPC1 (Guo et al. 2017). The crystal structure of this vacuolar two-pore channel, a homodimer, has been solved (Guo et al. 2015) (Kintzer and Stroud 2016). Activation requires both voltage and cytosolic Ca²⁺. Ca²⁺ binding to the cytosolic EF-hand domain triggers conformational changes coupled to the pair of pore-lining inner helices from the first 6-TMS domains, whereas membrane potential only activates the second voltage-sensing domain, the conformational changes of which are coupled to the pair of inner helices from the second 6-TMS domains. Luminal Ca²⁺ or Ba²⁺ modulates voltage activation by stabilizing the second voltage-sensing domain in the resting state and shift voltage activation towards more positive potentials. The basis for understanding ion permeation, channel activation, the location of voltage-sensing domains and regulatory ion-binding sites is partially explained by the 3-d structure (Kintzer and Stroud 2016). Only the second Shaker domain senses voltage (Jaślan et al. 2016). It has a selectivity filter that is passable by hydrated divalent cations (Demidchik et al. 2018). Dickinson et al. 2022 determined structures at different stages along its activation coordinate. These structures of activation intermediates, when compared with the resting-state structure, portray a mechanism in which the voltage-sensing domain undergoes dilation and in-membrane plane rotation about the gating charge-bearing helix, followed by charge translocation across the charge transfer seal. These structures, in concert with patch-clamp electrophysiology, showed that residues in the pore mouth sense inhibitory Ca²⁺ and are allosterically coupled to the voltage sensor. These conformational changes provide insight into the mechanism of voltage-sensor domain activation in which activation occurs vectorially over a series of elementary steps (Dickinson et al. 2022). Inhibition of the Akt/PKB kinase increases Nav1.6-mediated currents and neuronal excitability in CA1 hippocampal pyramidal neurons (Marosi et al. 2022).	Eukaryota	Viridiplantae, Streptophyta	TPC1 of Arabidopsis thaliana
1.A.1.11.27	Voltage-dependent P/Q-type Ca²⁺ channel subunit α1A, CACNA1A (CACH4; CACN3; CACNL1A4) of 2,505 aas. The CACNA1A gene is widely expressed throughout the CNS. The encoding protein is 90% identical to 1.A.1.11.8. Associated with four neurological phenotypes: familial and sporadic hemiplegic migraine type 1 (FHM1, SHM1), episodic ataxia type 2 (EA2), spinocerebellar ataxia type 6 (SCA6) and epileptic encephalopathy with nerve atrophy (Reinson et al. 2016). A gain of function mutation gave symptoms of congenital ataxia, abnormal eye movements and developmental delay with severe attacks of hemiplegic migraine (García Segarra et al. 2014). Mutations can cause F/SHM with high penitrance (Prontera et al. 2018). CACNA1A variants lead to a wide spectrum of neurological disorders including epileptic or non-epileptic paroxysmal events, cerebellar ataxia, and developmental delay. The variants are either gain of function GOF) or loss of function (LOF) mutations (Zhang et al. 2020). CACNA1A pathogenic variants have been linked to several neurological disorders including severe early onset developmental encephalopathies and cerebellar atrophy. Y1384 variants exhibit differential splice variant-specific effects on recovery from inactivation (Gandini et al. 2021). Patients with CACNA1A mutational variants located in the transmembrane region may be at high risk of status epilepticus (Niu et al. 2022). Patients with ataxia in the absence of epilepsy can be caused by a CACNA1A mutationand respond to pyridoxine (Du et al. 2017). lamotrigine can be used to treat patients with refractory epilepsy due to calcium channel mutations (Hu et al. 2022; De Romanis and Sopranzi 2018). Eupatilin depresses glutamate exocytosis from cerebrocortical synaptosomes by decreasing P/Q-type Ca²⁺ channels and synapsin I phosphorylation and alleviates glutamate excitotoxicity caused by kainic acid by preventing glutamatergic alterations in the mamalian cortex. Thus, eupatilin is a potential therapeutic agent in the treatment of brain impairment associated with glutamate excitotoxicity (Lu et al. 2022). Episodic ataxia (EA2) is caused by mutations in CACNA1A, encoding a neuronal voltage-gated calcium channel (Graves et al. 2024). Albiflorin decreases glutamate release from rat cerebral cortex nerve terminals (synaptosomes) through depressing P/Q-type calcium channels and protein kinase A activity (Lu et al. 2024).	Eukaryota	Metazoa, Chordata	CACNA1A Ca²⁺ channel of Homo sapiens
1.A.1.11.28	Voltage-dependent L-type calcium channel subunit α, VDCC, CCA-1 or CaACNa1S, of 1873 aas and 24 TMSs. Ca²⁺ channels containing the alpha-1S subunit play an important role in excitation-contraction coupling in skeletal muscle. They are regulated by dystrophin-1 (Zhan et al. 2014).	Eukaryota	Metazoa, Nematoda	VDCC of Caenorhabditis elegans
1.A.1.11.29	Voltage-gated calcium channel (VDCC) of 3097 aas and 24 TMSs, Cav7 (Wheeler and Brownlee 2008). The photoreceptor potential in Chlamydomonas triggers the generation of all or no flagellar Ca²⁺ currents that cause membrane depolarization across the eyespot and flagella (Sanyal et al. 2023). Modulation in membrane potential causes changes in the flagellar waveform, and hence, alters the beating patterns of Chlamydomonas flagella. The eyespot membrane potential is rhodopsin-mediated and is generated by the photoreceptor Ca²⁺ current or P-current. However, flagellar Ca²⁺ currents are mediated by unidentified voltage-gated calcium (VGCC or CaV) and potassium channels (VGKC). The voltage-dependent ion channel that associates with ChRs to generate Ca²⁺ influx across the flagella and its cellular distribution has been identified. Sanyal et al. 2023 presented evidence on Chlamydomonas reinhardtii predicting that CrVGCC4 localizes to the eyespot and flagella and associates with channelrhodopsins. Further in silico interactome analysis of CrVGCCs suggested that they interact with photoreceptor proteins, calcium signaling, and intraflagellar transport components. Expression analysis indicated that these VGCCs and their putative interactors can be perturbed by light stimuli. Thus, VGCCs in general, and VGCC4 in particular, might be involved in the regulation of the phototactic response of Chlamydomonas.		Viridiplantae, Chlorophyta	Cav7 of Chlamydomonas reinhardtii
1.A.1.11.30	TPC calcium channel protein with two transmembrane domains of 6 TMSs each (720 aas and 12 TMSs) (Wheeler and Brownlee 2008).		Viridiplantae, Streptophyta	TPC of Physcomitrella patens
1.A.1.11.31	Voltage-sensitive calcium channel (VSCC), CA_V1.3, encoded by the CACNA1D gene, of 2161 aas and 24 TMSs (Singh et al. 2008). Ca_V1.3-R990H channels conduct omega-currents at hyperpolarizing potentials, but not upon membrane depolarization compared with wild-type channels (Monteleone et al. 2017). A CACNA1D de novo mutation causes a severe neurodevelopmental disorder (Hofer et al. 2020). Snapin (a synaptic junction complex (see TC# 1.F.1.1.1) directly interacts with the C-terminal extension (long) of Ca_v1.3_L, leading to up-regulation of Ca_v1.3_L channel activity via facilitating channel opening probability (Jeong et al. 2021).	Bacteria	Metazoa, Chordata	CAv1.3 of Homo sapiens
1.A.1.11.32	Pore-forming, alpha-1S subunit of the voltage-gated calcium channel, of 1873 aas and 24 TMSs, Cav1.1; CACNA1S; CACN1; CACH1; CACNL1A3, that gives rise to L-type calcium currents in skeletal muscle. Calcium channels containing the alpha-1S subunit play an important role in excitation-contraction coupling in skeletal muscle via their interaction with RYR1, which triggers Ca²⁺ release from the sarcplasmic reticulum and ultimately results in muscle contraction. Long-lasting (L-type) calcium channels belong to the 'high-voltage activated' (HVA) group (Jiang et al. 2018). The 3-d structure of a bacterial homologue has been solved (Jiang et al. 2018). Mutations in arginly residues in the TMS4 voltage lead to increased leak currently that may be responsible for hypokalaemic periodic paralysis (Kubota et al. 2020). Mutations in the voltage sensor domain of CaV1.1, the alpha1S subunit of the L-type calcium channel in skeletal muscle cause hypokalemic periodic paralysis (HypoPP), and these mutations give rise to gating pore currents (Wu et al. 2021). The voltage-gated T-type calcium channel is modulated by kinases and phosphatases (Sharma et al. 2023). Advances in Ca_V1.1 gating, dealing with permeation and voltage-sensing mechanisms, have been reviewed (Bibollet et al. 2023). It is possible to prevent calcium leak associated with short-coupled polymorphic ventricular tachycardia in patient-derived cardiomyocytes (Sleiman et al. 2023). Far-infrared ameliorates Pb-induced renal toxicity via voltage-gated calcium channel-mediated calcium influx (Ko et al. 2023). Verapamil mitigates chloride and calcium bi-channelopathy in a myotonic dystrophy mouse model (Cisco et al. 2024).		Metazoa, Chordata	Cav1.1 of Homo sapiens
1.A.1.11.33	Calcium channel protein of 2556 aas and 24 TMSs. Inhibited by 1,4-dihydrophyridines such as nifedipine (Tempone et al. 2009). The effects of nifedipine and calcium ions on cellular electrophysiology have been examined (Tsai et al. 2021).	Eukaryota	Euglenozoa	Ca²⁺ channel of Leishmania donovani
1.A.1.11.34	Calcium channel of 913 aas and 12 TMSs. Ca²⁺ channels in trophozoites are inhibited by Amlodipine (Baig et al. 2013).	Eukaryota	Discosea	Calcium channel of Acanthamoeba castellanii
1.A.1.11.35	Calcium channel of 2725 aas and 24 TMSs. T. cruzi calcium channels are inhibited by fendiline and bepridil (Reimão et al. 2011).	Eukaryota	Euglenozoa	Ca²⁺ channel of Trypanosoma cruzi
1.A.1.11.36	Two pore segment channel 1 of 790 aas and 12 TMSs in a 3 + 3 (N-terminal half) + 2 + 2 + 2 (C-terminal half) TMS arrangement. In the trunk of developing zebrafish embryos, adjacent myotome blocks transmit contractile force via myoseptal junctions (MJs), dynamic structures that connect the actin cytoskeleton of skeletal muscle cells to extracellular matrix components via transmembrane protein complexes in the sarcolemma. Rice et al. 2022 reported that the endolysosomal ion channel, TPC1, generates highly localized, non-propagating Ca²⁺ transients that play a distinct and required role in the capture and attachment of superficial slow skeletal muscle cells (SMCs) at MJs. Disruption of the tpcn1 gene resulted in abnormal MJ phenotypes including SMCs detaching from or crossing the myosepta. TPC1-decorated endolysosomes are dynamically associated with MJs in a microtubule-dependent manner, and attenuating tpcn1 expression or function disrupted endolysosomal trafficking and resulted in an abnormal distribution of beta-dystroglycan (a key transmembrane component of the dystrophin-associated protein complex). Thus, localized TPC1-generated Ca²⁺ signals facilitate essential endolysosomal trafficking and membrane contact events, which help form and maintain MJs following the onset of SMC contractile activity (Rice et al. 2022).	Eukaryota	Metazoa, Chordata	TPC1 of Danio rerio (Zebrafish) (Brachydanio rerio)
1.A.1.12.1	Paramecium bursaria Chlorella virus 1 (PBCV-1) K⁺ channel, Kcv1. (The viral-encoded K⁺ channel inserts into the green algal host membrane to aid ejection of DNA from the viral particle into the cytoplasm (Neupartl et al., 2007)). It may mediate host cell membrane depolarization and K⁺ loss (Agarkova et al., 2008; Balss et al., 2008). It is inhibited by Ba²⁺ and amantidine. (Reviewed by Thiel et al., 2010). The presence of charged amino acids which form dynamic inter- and intra- subunit salt bridges is crucial for channel activity (Hertel et al. 2010).	Viruses	Bamfordvirae, Nucleocytoviricota	Kcv1 K⁺ channel of Chlorella virus PBCV-1
1.A.1.12.2	Acanthocystis turfacea chlorella virus cation, K⁺-preferring, channel, ATCV1 (82aas and 2 TMSs) (Gazzarrini et al., 2009; Siotto et al. 2014). The difference in open probability between close isoforms is caused by one long closed state in Kcv_S versus Kcv_NTS. This state is structurally created in the tetrameric channel by a transient, Ser mediated, intrahelical hydrogen bond. The resulting kink in the inner transmembrane domain swings the aromatic rings from downstream Phenylalanines in the cavity of the channel, which blocks ion flux. The most conserved region of the Kcv protein is the filter, the turret and the pore helix, and the outer and the inner transmembrane domains of the protein are the most variable (Murry et al. 2020).	Viruses	Bamfordvirae, Nucleocytoviricota	ATCV1 (KCVS/KCVNTS) of Acanthocystis turfacea chlorella virus (A7K9J5)
1.A.1.12.3	The viral K⁺channel, Kesv of 124 aas. It is inhibited by Ba²⁺ and amantidine. It is important for infection and replication in marine brown algae (Chen et al. 2005; Balss et al., 2008; Siotto et al. 2014). A combination of hydrophobicity and codon usage bias determines sorting of the Kesv K⁺ channel protein to either mitochondria or the endoplasmic reticulum (Engel et al. 2023).	Viruses	Bamfordvirae, Nucleocytoviricota	Kesv of Ectocarpus siliculosus virus 1 (Q8QN67)
1.A.1.12.4	Viral K⁺ channel of 96 aas and 2 TMSs, Kcv (Siotto et al. 2014). Mechanical perturbation of the N-terminus can be transmitted to the C-terminal channel gates (Hoffgaard et al. 2015).	Viruses	Bamfordvirae, Nucleocytoviricota	Kcv of Paramecium bursaria Chlorella virus
1.A.1.12.5	Potassium ion channel protein of 86 aas and 2 TMSs (Greiner et al. 2018).	Viruses	Bamfordvirae, Nucleocytoviricota	K⁺ channel protein of Micromonas pusilla virus SP1
1.A.1.12.6	Potassium channel of 101 aas and 2 TMSs (Kukovetz et al. 2020).	Viruses		K+ channel of Rhizochromulina virus RhiV-SA1
1.A.1.13.1	6TMS K⁺ channel (Munsey et al. 2002; Kuo et al., 2003). The kch gene, the only known potassium channel gene in E. coli, has the property to express both full-length Kch and its cytosolic domain (RCK) due to a methionine at position 240. The RCK domains form an octameric ring structure and regulate the gating of the potassium channels after having bound certain ligands. Several different gating ring structures have been reported for the soluble RCK domains. The octameric structure of Kch may be composed of two tetrameric full-length proteins through RCK interaction (Kuang et al. 2013). The RCK domains face the solution, and an RCK octameric gating ring arrangement does not form under certain conditions (Kuang et al. 2015).	Bacteria	Pseudomonadota	Kch of E. coli
1.A.1.13.2	2 TMS ( P-loop) Ca²⁺-gated K⁺ channel, MthK (see Jiang et al., 2002 for the crystal structure, and Parfenova et al., 2006 for mutations affecting open probability). For the studies of ion permeation and Ca²⁺ blockage, see Derebe et al., 2011. (structures: 3LDD_A and 2OGU_A.). Voltage-dependent K⁺ channels including MthK which lacks a canonical voltage sensor can undergo a gating process known as C-type inactivation, which involves entry into a nonconducting state through conformational changes near the channel's selectivity filter (Thomson and Rothberg, 2010). C-type inactivation may involve movements of transmembrane voltage sensor domains. In the absence of Ca²⁺, a single structure in a closed state was observed by cryoEM that was highly flexible with large rocking motions of the gating ring and bending of pore-lining helices (Fan et al. 2020). In Ca²⁺-bound conditions, several open-inactivated conformations were present with the different channel conformations being distinguished by rocking of the gating rings with respect to the transmembrane region. In all conformations displaying open channel pores, the N-terminus of one subunit of the channel tetramer sticks into the pore and plugs it. Deletion of this N terminus led to non-inactivating channels with structures of open states without a pore plug, indicating that this N-terminal peptide is responsible for a ball-and-chain inactivation mechanism (Fan et al. 2020). Lipid-protein interactions influence the conformational equilibrium between two states of the channel that differ according to whether a TMS has a kink. Two key residues in the kink region mediate crosstalk between two gates at the selectivity filter and the central cavity, respectively. Opening of one gate eventually leads to closure of the other (Gu and de Groot 2020). Activation of MthK is exquisitely regulated by temperature (Jiang et al. 2020).	Archaea	Euryarchaeota	MthK of Methanothermobacter thermoautotrophicus (Methanobacterium thermoautotrophicum)(O27564)
1.A.1.13.3	Divalent cation (Ca²⁺, Mg²⁺, Mn²⁺, Ni²⁺)-activated K⁺ channel, TuoK (contains a RCK domain) (Parfenova et al., 2007)	Archaea	Candidatus Thermoplasmatota	TuoK of Thermoplasma volcanium (Q979Z2)
1.A.1.13.4	The Biofilm-inducing putative K⁺ channel, BikC or YugO (Prindle et al. 2015). BikC has an N-terminal 2 TMS + P-loop channel domain and a C-terminal NADB_Rossman superfamily domain (TrkA domain). YugO is in a two cistronic operon where Mistic (MstX; 9.A.66; Debnath et al., 2011; Roosild et al., 2005) is encoded by the gene that precedes yugO. Both play a role in biofilm formation, probably by functioning together (Lundberg et al. 2013; Marino et al. 2015). These K⁺ channels in bacterial biofilms provide an active, long-range electrical signalling for cellular communities (Prindle et al. 2015). Metabolic co-dependency gives rise to collective electrical oscillations in biofilms (Liu et al. 2015). This oscillatory electrical signalling, due to periodic release of K⁺, giving rise to K⁺ gradients, increasing as swimming cells approach the biofilm that generates the gradiens, allows cells of the same and different speices to find and then incorporate themselves into existing biofilms (Humphries et al. 2017).	Bacteria	Bacillota	BikC of Bacillus subtilis (Q795M8)
1.A.1.13.5	Putative 2 TMS ion channel protein (N-terminus) with C-terminal TrkA_N (NADB Rossman) domain.	Bacteria	Actinomycetota	Ion channel protein of Streptomyces coelicolor
1.A.1.13.6	Ca²⁺-activated K⁺ channel, SynCaK. Functions in the regulation of photosynthesis (Checchetto et al. 2013; Checchetto et al. 2013).	Bacteria	Cyanobacteriota	K⁺ channel of Synechocystis PCC6803
1.A.1.13.7	Putative K⁺ channel, TrkA1, of 365 aas and 2 N-terminal TMSs, with a C-terminal NAD binding domain.	Bacteria	Cyanobacteriota	K⁺ channel of Synechocystis PCC6803
1.A.1.13.8	Potassium channel protein, MjK1 of 333 aas and 6 TMSs. Seems to conduct potassium at low membrane potentials (Hellmer and Zeilinger 2003). Also called TrkA3, a Trk channel with a C-terminal NAD-binding domain.	Archaea	Euryarchaeota	MjK1 of Methanocaldococcus jannaschii (Methanococcus jannaschii)
1.A.1.13.9	K⁺ channel of 387 aas and 2 TMSs, KchA. KchA is essential for growth at low concentrations of K⁺. This K⁺uptake system is essential for gastric colonization and the persistence of H. pyloriin the stomach (Stingl et al. 2007). This protein is of the two-transmembrane RCK (regulation of K⁺ conductance) domain family (Stingl et al. 2007).	Bacteria	Campylobacterota	KchA of Helicobacter pylori
1.A.1.13.10	K⁺ channel protein with 343 aas and 2 N-terminal TMSs, MjK2. Binding of the MjK2 RCK domain to membranes takes place via an electrostatic interaction with anionic lipid surfaces (Ptak et al. 2005).	Archaea	Euryarchaeota	MjK2 of Methanocaldococcus jannaschii (Methanococcus jannaschii)
1.A.1.14.1	Voltage-activated, Ca²⁺ channel blocker-inhibited, Na⁺ channel, NaChBac (Ren et al., 2001; Zhao et al., 2004; Nurani et al, 2008; Charalambous and Wallace, 2011). Arginine residues in the S4 segment play a role in voltage-sensing (Chahine et al. 2004). Transmembrane and extramembrane regions contribute to thermal stability (Powl et al., 2012). Deprotonation of arginines in S4 is involved in NaChBac gating (Paldi, 2012). Hinge-bending motions in the pore domain of NaChBac have been reported (Barber et al., 2012). The C-terminal coiled-coli stabilizes subunit interactions (Mio et al. 2010). Within the 4 TMS voltage sensor, coupling between residues in S1 and S4 determines its resting conformation (Paldi and Gurevitz 2010). The conserved asparagine was changed to aspartate, N225D, and this substitution shifted the voltage-dependence of inactivation by 25 mV to more hyperpolarized potentials. The mutant also displays greater thermostability (O'Reilly et al. 2017). Possibly, the side-chain amido group of asn₂₂₅ forms one or more hydrogen bonds with different channel elements, and these interactions are important for normal channel function. The T1-tetramerization domain of Kv1.2 (TC# 1.A.1.2.10) rescues expression and preserves the function of a truncated form of the NaChBac sodium channel (D'Avanzo et al. 2022). The structure of NaChBac embedded in liposomes has been solved by cryo electron tomography (Chang et al. 2023). The small channel has most of its residues embedded in the membrane, and these are flexible, determining the channel dimensions.	Bacteria	Bacillota	NaChBac of Bacillus halodurans
1.A.1.14.2	Voltage-gated Na⁺ channel, Na_vPZ (Koishi et al., 2004)	Bacteria	Pseudomonadota	Na_vPZ of Paracoccus zeaxanthinifaciens (CAD24429)
1.A.1.14.3	Na⁺ channel, Na_vBP, involved in motility, chemotaxis and pH homeostasis (Ito et al., 2004). Na_vBP colocalizes with a methyl-accepting chemotaxis protein (MCP) at the cell poles (Fujinami et al., 2007).	Bacteria	Bacillota	Na_vBP of Bacillus pseudofirmus (AAT21291)
1.A.1.14.4	Voltage-gated Na⁺ channel, VGSC (Koishi et al., 2004; McCusker et al., 2011) Changing the selectivity filter from LESSM to LDDWSD yielded a Calcium-selective channel (Shaya et al., 2011).	Bacteria	Pseudomonadota	VGSC of Silicibacter pomeroyi (56676695)
1.A.1.14.5	Voltage-gated Na⁺ channel, Na_vCh or Na_vAb. The 3d-structure is known (3ROW; Payandeh et al., 2011; 4MW3A-D; 4+ selectivity through partial dehydration of Na⁺ via its direct interaction with conserved glutamate side chains). The pore is preferentially occupied by two ions, which can switch between different configurations by crossing low free-energy barriers (Furini and Domene, 2012). Jiang et al. 2018 presented high-resolution structures of NavAb with the analogous gating-charge mutations that have similar functional effects as in the human channels that cause hypokalaemic and normokalaemic periodic paralysis. Wisedchaisri et al. 2019 presented a cryo-EM structure of the resting state and a complete voltage-dependent gating mechanism via the voltage sensor (VS). The S4 segment of the VS is drawn intracellularly, with three gating charges passing through the transmembrane electric field. This movement forms an elbow connecting S4 to the S4-S5 linker, tightens the collar around the S6 activation gate, and prevents its opening. This structure supports the classical "sliding helix" mechanism of voltage sensing and provides a complete gating mechanism for voltage sensor function, pore opening, and activation-gate closure based on high-resolution structures of a single sodium channel protein (Wisedchaisri et al. 2019). (see also TC#s 1.A.1.10.4 and 1.A.1.11.32). The transport reaction catalyzed by Na_vCh is: Na⁺ (in) ⇌ Na⁺ (out)	Bacteria	Campylobacterota	Na_vCh of Arcobacter butzleri (A8EVM5)
1.A.1.14.6	Bacterial voltage-gated sodium channel, Nav. 3-d crystal structures of vaious conformations are known (4P_3A A-D; 4PA7_A-D; 4P9P_A-D. etc.) (McCusker et al. 2012). It has its internal cavity accessible to the cytoplasmic surface as a result of a bend/rotation about a central residue in the carboxy-terminal TMS that opens the gate to allow entry of hydrated sodium ions. The molecular dynamics of ion transport through the open conformation has been analyzed (Ulmschneider et al. 2013). The C-terminal four helix coiled coil bundle domain couples inactivation with channel opening, depedent on the negatively charged linker region (Bagnéris et al. 2013). A NaVSp1-specific S4-S5 linker peptide induced both an increase in NaVSp1 current density and a negative shift in the activation curve, consistent with the S4-S5 linker stabilizing the open state (Malak et al. 2020).	Bacteria	Pseudomonadota	Nav of Magnetococcus marinus (also called sp. strain MC-1)
1.A.1.14.7	Tetrameric 6 TMS subunit Na⁺ channel protein, Na_V. Two low resolution cyroEM structures revealed two conformations reconstituted in lipid bilayers (Tsai et al. 2013). Despite a voltage sensor arrangement identical with that in the activated form, Tsai et al. 2013 observed two distinct pore domain structures: a prominent form with a relatively open inner gate, and a closed inner-gate conformation similar to the first prokaryotic Na_v structure. Structural differences, together with mutational and electrophysiological analyses, indicated that widening of the inner gate was dependent on interactions among the S4-S5 linker, the N-terminal part of S5 and its adjoining part in S6, and on interhelical repulsion by a negatively charged C-terminal region subsequent to S6 (Tsai et al. 2013).	Bacteria	Bacillota	Nav of Caldalkalibacillus thermarum
1.A.1.14.8	Voltage-gated Na⁺ channel, Nsv, of 277 aas and 6 TMSs with a structually defined C-terminal regulatory domain (Miller et al. 2016). Voltage-gated sodium channels (Na_Vs) are activated by transiting the voltage sensor from the deactivated to the activated state. Tang et al. 2017 identified peptide toxins stabilizing the deactivated VSM of bacterial Na_Vs. A cystine knot toxin, called JZTx-27, from the venom of the tarantula Chilobrachys jingzhao proved to be a high-affinity antagonist. JZTx-27 stabilizes the inactive form of the voltage sensor, thereby inhibiting channel activity (Tang et al. 2017).		Bacillota	Nsv of Bacillus alcalophilus
1.A.1.14.9	Bacterial type voltage-activated sodium channel of 718 aas, NaV.	Eukaryota	Bacillariophyta	NaV of Phaeodactylum tricornutum
1.A.1.15.1	6 TMS basolateral tracheal epithelial cell/voltage-gated, small conductance, K⁺ α-chain, KCNQ1, [acts with the KCNE3 β-chain]. Mutations in human K_v7 genes lead to severe cardiovascular and neurological disorders such as the cardiac long QT syndrome and neonatal epilepsy (Haitin and Attali, 2008). KCNE3 can co-assemble with KCNQ1 (1.A.1.15.6) (Kang et al., 2010). KCNQ1 regulates insulin secretion in the MIN6 beta-cell line (Yamagata et al., 2011). The S4-S5 linker of KCNQ1 forms a scaffold with S6 controlling gate closure (Labro et al. 2011). The KCNQ1 channel is differentially regulated by KCNE1 and KCNE2 (Li et al. 2014. Slow-activating channel complexes formed by KCNQ1 and KCNE1 are essential for human ventricular myocyte repolarization, while constitutively active KCNQ1-KCNE3 channels are important in the intestine. Inherited sequence variants in human KCNE1 and KCNE3 cause cardiac arrhythmias but by different mechanisms, and each is important for hearing in unique ways (Abbott 2015). The topology and dynamics of the voltage sensor domain of KCNQ1 reconstituted in a lipid bilayer environment has been studied (Dixit et al. 2019). KCNQ1 (Kv 7.1) alpha-subunits and KCNE1 beta-subunits co-assemble to form channels that conduct the slow delayed rectifier K⁺ current (IKs) in the heart. Mutations in either subunit cause long QT syndrome (LQTS), an inherited disorder of cardiac repolarization (Seebohm et al. 2005). KCNE1 modulates KCNQ1 potassium channel activation by an allosteric mechanism (Kuenze et al. 2020). The membrane electric field regulates the PIP₂-binding site to gate the KCNQ1 channel (Mandala and MacKinnon 2023).	Eukaryota	Metazoa, Chordata	KCNQ1 K⁺ channel of Mus musculus
1.A.1.15.2	6 TMS voltage-gated K⁺ channel, KCNQ2 or Kv7.2. Mutations cause benign familial neonatal convulsions (BNFC; epilepsy; Maljevic et al. 2016; Soldovieri et al. 2019). It forms homotetramers or heterotetramers with KCNQ3/Kv7.3) (Soldovieri et al., 2006; Uehara et al., 2008)). Like all other Kv7.2 channels, it is activated by phosphatidyl inositol-4,5-bisphosphate and hence can be regulated by various neurotransmitters and hormones (Telezhkin et al. 2013). Gating pore currents that go through the gating pores in TMSs1-4 (the voltage sensor) may give rise to peripheral nerve hyperexcitability (Moreau et al. 2014). Retigabine and ICA73, two anti-epileptic drugs, act via distinct mechanisms due to interactions with specific residues that underlie subtype specificity of KCNQ channel openers (Wang et al. 2016). A tight spatial and functional relationship between the DAT/GLT-1 transporters and the Kv7.2/7.3 potassium channel immediately readjusts the membrane potential of the neuron, probably to limit the neurotransmitter-mediated neuronal depolarization (Bartolomé-Martín et al. 2019). E-2-dodecenal from cilantro (Coriandrum sativum) is a potent activator and anticonvulsant that binds with an affinity of 60 nM to TMS5 in several KCNQ channels including KCNQ2 and 3 (Manville and Abbott 2019). The activities of Kv7 channels are modulated by polyunsaturated fatty acids (Larsson et al. 2020). Anticancer effects of FS48 from salivary glands of Xenopsylla cheopis via its blockage of voltage-gated K⁺ channels has been demonstrated (Xiong et al. 2023). The drug, ezogabine restoresnormal activity ,decreasing depressive symptoms in major depressive disorder patients (Costi et al. 2021). Both L- and D-isomers of S-nitrosocysteine (CSNO) can bind to the intracellular domain of voltage-gated potassium channels in vitro. CSNO binding inhibits these channels in the carotid body, leading to increased minute ventilation in vivo (Krasinkiewicz et al. 2023).	Eukaryota	Metazoa, Chordata	KCNQ2 K⁺ channel of Homo sapiens (O43526)
1.A.1.15.3	6 TMS voltage-gated K⁺ channel, KCNQ3 or K_v7.3. Mutations cause benign familial neonatal convulsions (BNFC; epilepsy; Maljevic et al. 2016). Forms homotetramers or heterotetramers with KCNQ2 (Soldovieri et al., 2006; Uehara et al., 2008). Retigabine and ICA73, two anti-epileptic drugs, act via distinct mechanisms due to interactions with specific residues that underlie subtype specificity of KCNQ channel openers (Wang et al. 2016). Gabapentin at low concentrations is a activator of KCNQ3, KCNQ2/3 and KCNQ5 but not KCNQ2 or KCNQ4 (Manville and Abbott 2018). At high concentrations it can be inhibitory. A tight spatial and functional relationship between the DAT/GLT-1 transporters and the Kv7.2/7.3 potassium channel immediately readjusts the membrane potential of the neuron, probably to limit the neurotransmitter-mediated neuronal depolarization (Bartolomé-Martín et al. 2019). E-2-dodecenal from cilantro (Coriandrum sativum) is a potent activator and anticonvulsant that binds with an affinity of 60 nM to TMS5 in several KCNQ channels including KCNQ2 and 3 (Manville and Abbott 2019). Pathogenic variants in KCNQ2 and KCNQ3, paralogous genes encoding Kv7.2 and Kv7.3 voltage-gated K⁺ channel subunits, are responsible for early-onset developmental/epileptic disorders characterized by heterogeneous clinical phenotypes ranging from benign familial neonatal epilepsy (BFNE) to early-onset developmental and epileptic encephalopathy (DEE). KCNQ2 variants account for the majority of pedigrees with BFNE, and KCNQ3 variants are responsible for a much smaller subgroup (Miceli et al. 2020). The M240R variant mainly affects the voltage sensitivity, in contrast to previously analyzed BFNE Kv7.3 variants that reduce current density (Miceli et al. 2020).	Eukaryota	Metazoa, Chordata	KCNQ3 K⁺ channel of Homo sapiens (O43525)
1.A.1.15.4	6 TMS cell volume sensitive, voltage-gated K⁺ channel, KCNQ4 or Kv7.4 (mutations cause DFNA2, an autosomal dominant form of progressive hearing loss) (forms homomers or heteromers with KCNQ3) (localized to the basal membrane of cochlear outer hair cells and in several nuclei of the central auditory pathway in the brainstem). Four splice variants form heterotetramers; each subunit has different voltage and calmodulin-sensitivities (Xu et al., 2007). Autosomal dominant mutant forms leading to progressive hearing loss (DFNA2) have been characterized (Kim et al. 2011). Phosphatidylinositol 4,5-bisphosphate (PIP2) and polyunsaturated fatty acids (PUFAs) impact ion channel function (Taylor and Sanders 2016). This channel may be present in mitochondria (Parrasia et al. 2019). Polyunsaturated fatty acids are modulators of KV7 channels (Larsson et al. 2020). The pathogenicity classification of KCNQ4 missense variants in clinical genetic testing has been described (Zheng et al. 2022). KCNQ4 potassium channel subunit deletion leads to exaggerated acoustic startle reflex in mice (Maamrah et al. 2023).	Eukaryota	Metazoa, Chordata	KCNQ4 K⁺ channel of Homo sapiens
1.A.1.15.5	The KCNQ5 K⁺ channel (modulated by Zn²⁺, pH and volume change) (Jensen et al., 2005). A triple cysteine module within M-type K⁺ channels mediates reciptrocal channel modulation by nitric oxide and reactive oxygen species (Ooi et al. 2013). Gabapentin at low concentrations is a activator of KCNQ3, KCNQ2/3 and KCNQ5 but not of KCNQ2 or KCNQ4 (Manville and Abbott 2018). At high concentrations, it can be inhibitory. KCNQ5 controls perivascular adipose tissue-mediated vasodilation (Tsvetkov et al. 2024).	Eukaryota	Metazoa, Chordata	KCNQ5 of Mus musculus (Q9JK45)
1.A.1.15.6	K⁺ voltage-gated channel, LQT-like subfamily; Kv7.1; KvLQT1. KCNQ1 (regulated by KCNE peptides (TC# 8.A.58) affect voltage sensor equilibrium (Rocheleau and Kobertz, 2007). Almost 300 mutations of KCNQ1 have been identified in patients, and most are linked to the long QT syndrome (LQT1), some in the voltage sensor (Peroz et al., 2008; Eldstrom et al. 2010; Qureshi et al. 2013; Ikrar et al. 2008). KCNQ1-KCNE1 complexes may interact intermittently with the actin cytoskeleton via the C-terminal region (Mashanov et al., 2010). The stoichiometry of the KCNQ1 - KCNE1 complex is flexible, with up to four KCNE1 subunits associating with the four KCNQ1 subunits of the channel (Nakajo et al., 2010). A familial mutation in the voltage-sensor of the KCNQ1 channel results in a cardiac phenotype (Henrion et al., 2012). KCNQ1 regulates insulin secretion in the MIN6 beta-cell line (Yamagata et al., 2011; Gofman et al., 2012). Electrostatic interactions of S4 arginines with E1 and S2 contribute to gating movements of S4, but coupling requires the lipid phosphatidylinositol 4,5-bisphosphate (PIP2) as voltage-sensing domain activation failed to open the pore in the absence of PIP2 (Zaydman et al. 2013). The D242N mutation causes impaired action potential adaptation to exercise and an increase in heart rate. Moreover, the D242 amino acyl position is involved in the KCNE1-mediated regulation of the voltage-dependence of activation of the K_V7.1 channel (Moreno et al. 2017). The KCNQ1 channel interacts with MinK (KCNE1) to cause pore constriction, generating the slow delayed rectifier (IKs) current in the heart (Jalily Hasani et al. 2018). KCNQ1 rescues TMC1 plasma membrane expression but not mechanosensitive channel activity (Harkcom et al. 2019). Activation of the neuronal Kv7/KCNQ/M-current represents an attractive therapeutic strategy for treatment of hyperexcitability-related neuropsychiatric disorders such as epilepsy, pain, and depression, and channel openers for treatment of antiepilepsy have been developed (Zhang et al. 2019). The relationship between mutation locations in KCNQ1, which is a major gene in long QT syndrome (LQTS), and phenotype has been analyzed and used for risk stratification (Yagi et al. 2018). The proximal C-terminal regions of KCNQ1 and KCNE1 participate in a physical and functional interaction during channel opening that is sensitive to perturbation (Chen et al. 2019). Retigabine analogs are activators of Kv7 channels (Ostacolo et al. 2020). People with borderline QTc prolongations were carriers of KCNQ1 mutations in TMSs 2 and 5, leading to haploinsufficiency, and they are potentially at risk of developing drug-induced arrhythmia (Gouas et al. 2004). Collision induced unfolding differentiates functional variants of the KCNQ1 voltage sensor domain (Fantin et al. 2020). The activated KCNQ1 channel promotes a fibrogenic response in hereditary gingival fibromatosis via clustering and activation of Ras (Gao et al. 2020). QT syndrome (LQTS) increases the risk of life-threatening arrhythmia in young individuals with structurally normal hearts. It may involve sixteen genes such as the KCNQ1, KCNH2, and SCN5A (Lin et al. 2020). The human KCNQ1 voltage sensing domain (VSD) has been studied in lipodisq nanoparticles by electron paramagnetic resonance (EPR) spectroscopy (Sahu et al. 2020). Structural mechanisms for the activation of the human cardiac KCNQ1 channel by electro-mechanical coupling enhancers have been reviewed (Ma et al. 2022). The pathogenicity of KCNQ1 variants using zebrafish as a model has been reviewed (Cui et al. 2023). Phosphatidyl-inositol-4,5-bisphosphate (PIP₂) is required for coupling between the voltage sensor and the pore of the potassium voltage-gated K_V7 channel family, especially the K_V7.1 channel. Modulation of the I(KS) channel by PIP₂ requires two binding sites per monomer (Kongmeneck et al. 2023). Divergent regulation of the KCNQ1/E1 channel can be accomplished by targeted recruitment of protein kinase A to distinct sites on the channel complex (Zou et al. 2023). Rare missense variants with a clear phenotype of Long QT Syndrome, type 1 (LQTS) have a high likelihood to be present within the pore and adjacent TMSs (S5-Pore-S6) (Novelli et al. 2023). LHFPL5 is a key element in force transmission from the tip link to the hair cell mechanotransducer channel (Harkcom et al. 2019). Activation of the neuronal Kv7/KCNQ/M-current represents an attractive therapeutic strategy for treatment of hyperexcitability-related neuropsychiatric disorders such as epilepsy, pain, and depression, and channel openers for treatment of antiepilepsy have been developed (Zhang et al. 2019). The relationship between mutation locations in KCNQ1, which is a major gene in long QT syndrome (LQTS), and phenotype has been analyzed and used for risk stratification (Yagi et al. 2018). The proximal C-terminal regions of KCNQ1 and KCNE1 participate in a physical and functional interaction during channel opening that is sensitive to perturbation (Chen et al. 2019). Retigabine analogs are activators of Kv7 channels (Ostacolo et al. 2020). People with borderline QTc prolongations were carriers of KCNQ1 mutations in TMSs 2 and 5, leading to haploinsufficiency, and they are potentially at risk of developing drug-induced arrhythmia (Gouas et al. 2004). Collision induced unfolding differentiates functional variants of the KCNQ1 voltage sensor domain (Fantin et al. 2020). The activated KCNQ1 channel promotes a fibrogenic response in hereditary gingival fibromatosis via clustering and activation of Ras (Gao et al. 2020). QT syndrome (LQTS) increases the risk of life-threatening arrhythmia in young individuals with structurally normal hearts. It may involve sixteen genes such as the KCNQ1, KCNH2, and SCN5A (Lin et al. 2020). The human KCNQ1 voltage sensing domain (VSD) has been studied in lipodisq nanoparticles by electron paramagnetic resonance (EPR) spectroscopy (Sahu et al. 2020). Structural mechanisms for the activation of the human cardiac KCNQ1 channel by electro-mechanical coupling enhancers have been reviewed (Ma et al. 2022). The pathogenicity of KCNQ1 variants using zebrafish as a model has been reviewed (Cui et al. 2023). Phosphatidyl-inositol-4,5-bisphosphate (PIP₂) is required for coupling between the voltage sensor and the pore of the potassium voltage-gated K_V7 channel family, especially the K_V7.1 channel. Modulation of the I(KS) channel by PIP₂ requires two binding sites per monomer (Kongmeneck et al. 2023). Divergent regulation of the KCNQ1/E1 channel can be accomplished by targeted recruitment of protein kinase A to distinct sites on the channel complex (Zou et al. 2023). Rare missense variants with a clear phenotype of Long QT Syndrome, type 1 (LQTS) have a high likelihood to be present within the pore and adjacent TMSs (S5-Pore-S6) (Novelli et al. 2023). LHFPL5 is a key element in force transmission from the tip link to the hair cell mechanotransducer channel (Beurg et al. 2024).	Eukaryota	Metazoa, Chordata	KCNQ1 of Homo sapiens (P51787)
1.A.1.15.7	Ion channel transporter of 296 aas and 5 putative TMSs.	Bacteria	Mycoplasmatota	Ion channel of Mycoplasma sp. Pen4
1.A.1.15.8	KCNQ1 of 647 aas and 6 TMSs. Xiong et al. 2022 characterized KCNQ1 which functions in shell biomineralisation of pearl oyster, Pinctada fucata martensii.	Eukaryota	Metazoa, Mollusca	KCNQ1 of Pinctada fucata martensii
1.A.1.16.1	The small conductance Ca²⁺-activated K⁺ channel, SkCa2, Sk2 or Kcnn2 (not inhibited by arachidonate) (activated by three small organic molecules, the 1-EBIO and N5309 channel enhancers and the DCEBIO channel modulation (Pedarzani et al., 2005)). It is inhibited by protonation of outer pore histidine residues (Goodchild et al., 2009). The same is true for SK3 (K(Ca) 2.3 (Q9UGI6)). Regulates endothelial vascular function (Sonkusare et al., 2012). Distinct subcellular mechanisms enhance the surface membrane expression by its interacting proteins, α-actinin 2 (TC# 8.A.66.1.3) and filamin A (TC# 8.A.66.1.4) (Zhang et al. 2016). SK channel activators can compensate for age-related changes of the autorhythmic functions of the cerebellum (Karelina et al. 2017). SK2 proteins are more abundant in Purkinje cells than in the ventricular myocytes of normal rabbit ventricles (Reher et al. 2017). Apamin inhibits and isoproterenol activates this and other SK (KCNN) channels, and activation by isoproterenol is sex-dependent (Chen et al. 2018). Diverse interactions between KCa and TRP channels integrate cytoplasmic Ca²⁺, oxidative, and electrical signaling affecting cardiovascular physiology and pathology (Behringer and Hakim 2019). This channel may be present in mitochondria (Parrasia et al. 2019). A non-neuronal hSK3 isoform has a dominant-negative effect on hSK3 currents (Wittekindt et al. 2004). Medicinal plant products can interact with SKCa (Rajabian et al. 2022). Varients may cause conformational changes that alter the ability of the protein to modulate ion channel activities (d'Apolito et al. 2023).	Eukaryota	Metazoa, Chordata	SkCa2 of Homo sapiens
1.A.1.16.2	The intermediate conductance, Ca²⁺-activated K⁺ channel, IKCa, Kcnn4, SK4, Sk4, Smik, Ik1 hIK1, IKCa or KCa3.1, also called the Gardos channel, of 543 aas and 6 TMSs. It is inhibited by 1 μM arachidonate which binds in the pore (Hamilton et al., 2003)). Nucleoside diphosphate kinase B (NDPK-B) activates KCa3.1 via histidine phosphorylation, resulting in receptor-stimulated Ca²⁺ flux and T cell activation (Di et al., 2010). It regulates endothelial vascular function (Sonkusare et al., 2012). Tissue-specific expression of splice variants of the orthologous rat KCNN4 protein have been reported (Barmeyer et al. 2010). Residues involved in gating have been identified (Garneau et al. 2014). It is also present in the inner mitochondrial membrane where increases of mitochondrial matrix [Ca²⁺] cause mtKCa3.1 opening, thus linking inner membrane K⁺ permeability and transmembrane potential to Ca²⁺ signalling (De Marchi et al. 2009). KCa3.1 (IKCa) channels are expressed in CA1 hippocampal pyramidal cells and contribute to the slow afterhyperpolarization that regulates spike accommodation (Turner et al. 2016). SK channel activators can compensate for age-related changes of the autorhythmic functions of the cerebellum (Karelina et al. 2017). The activation mechanism has been revealed by the cryoEM structure of the SK4-calmodulin complex (Lee and MacKinnon 2018). It is responsible for hyperpolarization in some tumor cells (Lazzari-Dean et al. 2019). Mutations are linked to dehydrated hereditary stomatocytosis (xerocytosis) (Andolfo et al. 2015). This channel is present in mitochondria (Parrasia et al. 2019). KCNN4 promotes the progression of lung adenocarcinoma by activating the AKT and ERK signaling pathways (Xu et al. 2021). KCa3.1 channels in human microglia link extracellular ATP-evoked Ca²⁺ transients to changes in membrane conductance with an inflammation-dependent mechanism, and suggests that during brain inflammation, the KCa3.1-mediated microglial response to purinergic signaling may be reduced (Palomba et al. 2021). Both IK(Ca) and BK(Ca) regulate cell volume in human glioblastoma cells (Michelucci et al. 2023). Lysosomal Ca²⁺ release is sustained by ER→lysosome Ca²⁺ refilling and K⁺ efflux through the KCa3.1 channel in inflammasome activation and metabolic inflammation (Kang et al. 2024).	Eukaryota	Metazoa, Chordata	hIK1 of Homo sapiens (AAC23541)
1.A.1.16.3	Small conductance calcium-gated potassium (SK) channel. Three charged residues in TMS S6 of SK channels near the inner mouth of the pore collectively control the conductance and rectification through an electrostatic mechanism (Li and Aldrich, 2011). The SK channel inhibitors NS8593 and UCL1684 prevent the development of atrial fibrillation via atrial-selective inhibition of sodium channel activity (Burashnikov et al. 2020).	Eukaryota	Metazoa, Arthropoda	SK of Drosophila melanogaster (Q7KVW5)
1.A.1.16.4	Small conductance Ca²⁺-activated K⁺ channel, KCNL-2 of 672 aas. Plays a role in the rate of egg laying (Chotoo et al. 2013).	Eukaryota	Metazoa, Nematoda	KCNL-2 of Caenorhabditis elegans
1.A.1.16.5	Plasma membrane small conductance calcium-activated K⁺ channel of 396 aas, TSKCa; probably involved in immunoregulation (Cong et al. 2009).	Eukaryota	Metazoa, Chordata	TSKCa of Psetta maxima (Turbot) (Pleuronectes maximus)
1.A.1.16.6	Small conductance calcium-activated K⁺ channel, KCNN1 or SK, of 543 aas and 6 TMSs. It is a druggable risk factor for opioid use disorder (OUD) (Kember et al. 2022).	Eukaryota	Metazoa, Chordata	SK of Homo sapiens
1.A.1.16.7	Small conductance calcium-activated potassium channel protein 3 of 736 aas and 6 TMSs, SK3 or KCNN3. It forms a voltage-independent potassium channel, activated by intracellular calcium (Bauer et al. 2019). Activation is followed by membrane hyperpolarization and is thought to regulate neuronal excitability by contributing to the slow component of synaptic after-hyperpolarization. The channel is blocked by apamin. Contrary to its bradycardic effect in the sinus node, blockage of its current by apamin accelerates ventricular automaticity and causes repeated, nonsustained, ventricular tachycardia in normal ventricles. Ryanodine receptor 2 blockage reversed the apamin effects on ventricular automaticity (Wan et al. 2019). Dextran sodium sulfate treatment causes loss of transient relaxation due to downregulation of SK3 channels and may increase contractile responses due to increased Ca²⁺ sensitization of smooth muscle cells via protease-activated receptor_1 (PAR1) [TC# P25116; TC# 9.A.14.13.37] activation (Sung et al. 2022). The specificity of Ca²⁺-activated K⁺ channel modulation in atherosclerosis and aerobic exercise training has been discussed (Mokelke et al. 2022). Small conductance calcium-activated potassium (SK) channel-positive modulators prevent ferroptosis and excitotoxicity in neuronal cells (Zhang et al. 2024).	Eukaryota	Metazoa, Chordata	KCNN3 of Homo sapiens
1.A.1.16.8	Small conductance plasma membrane calcium-activated potassium channel of 553 aas and 6 TMSs (Paul et al. 2021).	Eukaryota	Euglenozoa	BK channel of Leishmania donovani
1.A.1.17.1	The archaeal voltage-regulated K channel, KvAP (Ruta et al., 2003). X-ray and solution structures are available. The latter shows phospholipid interactions with the isolated voltage sensor domain (Butterwick and MacKinnon 2010; Li et al. 2014). The gating-charge arginine in TMS4 of the voltage sensor forms part of the helical hairpin "paddle", and it moves 15-20 Å through the membrane to open the pore (Ruta et al., 2005). The orientation and depth of insertion of the voltage-sensing S4 helix has been determined (Doherty et al., 2010). A synthetic S6 segment derived from the KvAP channel self-assembles, permeabilizes lipid vesicles, and exhibits ion channel activity in bilayer lipid membrane (Verma et al., 2011). Thus the gating mechanism combines structural rearrangements and electric-field remodeling ( Li et al. 2014). KvAP has been reconstituted in Giant Unilamellar Vesicles (GUVs) (Garten et al. 2015). TMS4 (S4) which senses voltage also promotes membrane insertion of the voltage-sensor domain (Mishima et al. 2016). KvAP has a configuration consistent with a water channel, possibly underlying the conductance of protons, and other cations, through voltage-sensor domains (Freites et al. 2006). The structural dynamics of the paddle motif loop in the activated conformation of the KvAP voltage sensor have been studied from biophysical standpoints (Das et al. 2019). The S4 alpha-helix, which is straight in the experimental crystal structure solved under depolarized conditions (Vm approximately 0), breaks into two segments when the cell membrane is hyperpolarized (Vm << 0) and reversibly forms a single straight helix following depolarization (Vm = 0) ((Bignucolo and Bernèche 2020). The outermost segment of S4 translates along the normal to the membrane, bringing new perspective to previously paradoxical accessibility experiments that were initially thought to imply the displacement of the whole VSD across the membrane. The breakage of S4 under (hyper)polarization could be a general feature of Kv channels with a non-swapped topology. The surface charge of the membrane does not significantly affect the topology and structural dynamics of the sensor loop in membranes (Das and Raghuraman 2021). The dynamic variability of the sensor loop is preserved in both zwitterionic (POPC) and anionic (POPC/POPG) lipid membranes. The lifetime distribution analysis for the NBD-labelled residues by the maximum entropy method (MEM) demonstrates that, in contrast to micelles, the membrane environment not only reduces the relative discrete population of sensor loop conformations, but also broadens the lifetime distribution peaks. The local curvature of cellular membranes acts as a driving force for the targeting of membrane-associated proteins to specific membrane domains, as well as a sorting mechanism for transmembrane proteins, as demonstrated for KvAP (Kluge et al. 2022). Conformational heterogeneity of the voltage sensor loop of the K⁺ channel, KvAP, in micelles and membranes has been documented (Das and Raghuraman 2021).	Archaea	Thermoproteota	KvAP of Aeropyrum pernix (Q9YDF8)
1.A.1.17.2	Voltage-gated K⁺channel, Kv (Santos et al., 2008).	Bacteria	Bacillota	Kv of Listeria monocytogenes (Q8Y5K1)
1.A.1.18.1	The two-pore domain potassium channel, TRESK-1 (Czirjak et al., 2004) (provides the background K⁺ current in mouse DRG neurons (Dobler et al., 2007)) TRESK (TWIK-related spinal cord K⁺ channel) is reversibly activated by the calcium/calmodulin-dependent protein phosphatase, calcineurin. Czirjak et al. 2008 reported that 14-3-3 proteins directly bind to the intracellular loop to TRESK and control the kinetics of the calcium-dependent regulation. Cloxyquin (5-chloroquinolin-8-ol) is an activator (Wright et al. 2013). A cytoplasmic loop binds tubulin (Enyedi et al. 2014). Channel activity is modified by phosphorylation (inactive) and dephosphorylation (active) of the unusually long intracellular loop between the 2nd and 3rd TMS (Lengyel et al. 2018). The distal short intracellular C-terminal region (iCtr) following the fourth TMS is a major positive determinant of TRESK function (Debreczeni et al. 2023).	Eukaryota	Metazoa, Chordata	TRESK-1 of Mus musculus (AAQ91836)
1.A.1.18.2	TRESK-2 or potassium channel subfamily K member 18 of 348 aas and 6 TMSs. TRESK-2 is a functional member of the K(2P) channel family and contributes to the background K⁺ conductance in many types of cells (Kang et al. 2004). The distal short intracellular C-terminal region (iCtr) following the fourth TMS is a major positive determinant of TRESK function (Debreczeni et al. 2023). Cloxyquin activates hTRESK by allosteric modulation of the selectivity filter (Schreiber et al. 2023).	Eukaryota	Metazoa, Chordata	TRESK-2 of Homo sapiens
1.A.1.19.1	Alkalinizatioin-activated Ca²⁺-selective channel, sperm-associated cation channel, CatSper, required for male fertility and the hyperactivated motility of spermatozoa (Kirichok et al. 2006). These channels require auxiliary subunits, CatSperβ, γ and δ for activity (Chung et al., 2011). The primary channel protein is CatSper1 (Liu et al., 2007), and it may be a target for immunocontraception (Li et al. 2009). CatSper channels have been reported to regulate sperm motility (Vicente-Carrillo et al. 2017). Sperm competition is selective for a disulfide-crosslinked macromolecular architecture. CatSper channel opening occurs in response to pH, 2-arachidonoylglycerol, and mechanical force. A flippase function is hypothesized, and a source of the concomitant disulfide isomerase activity is found in CatSper-associated proteins beta, delta and epsilon (Bystroff 2018). More recently, it has been reported that rotational motion and rheotaxis of human sperm do not require functional CatSper channels or transmembrane Ca²⁺ signaling (Schiffer et al. 2020). Instead, passive biomechanical and hydrodynamic processes may enable sperm rolling and rheotaxis, rather than calcium signaling mediated by CatSper or other mechanisms controlling transmembrane Ca²⁺ flux. The Ca²⁺ channel CatSper is not activated by cAMP/PKA signaling but directly affected by chemicals used to probe the action of cAMP and PKA (Wang et al. 2020). The cation channel of sperm (CatSper) is essential for sperm motility and fertility. CatSper comprises the pore-forming proteins CATSPER1-4 and multiple auxiliary subunits, including CATSPERbeta, gamma, delta, epsilon, zeta, and EFCAB9. Lin et al. 2021 reported the cryo-EM structure of the CatSper complex isolated from mouse sperm. CATSPER1-4 conform to the conventional domain-swapped voltage-gated ion channel fold, following a counterclockwise arrangement. The auxiliary subunits CATSPERbeta, gamma, delta and epsilon - each of which contains a single transmembrane segment and a large extracellular domain - constitute a pavilion-like structure that stabilizes the entire complex through interactions with CATSPER4, 1, 3 and 2, respectively. The EM map revealed several previously uncharacterized components, exemplified by the organic anion transporter SLCO6C1. Lin et al. 2021 named this channel-transporter ultracomplex the CatSpermasome. The assembly and organizational details of the CatSpermasome lay the foundation for the development of CatSpermasome-related treatments for male infertility and non-hormonal contraceptives. CatSper is a target for inhibition, for use in male contraception, causing inhibition of sperm motility (Mariani et al. 2023). A CUG-initiated CATSPERθ functions in the CatSper channel assembly and serves as a checkpoint for flagellar trafficking (Huang et al. 2023).	Eukaryota	Metazoa, Chordata	CatSper of Homo sapiens CatSper1 (Q96P76) CatSper3 (Q86XQ3) CatSper4 (Q7RTX7) CatSperβ (Q9H7T0) CatSperγ (Q6ZRH7) CatSperδ (Tmem146) (Q86XM0) CatSperε (B1AQM6) CatSperzeta (Q9NTU4) EFCAB9 (A8MZ26) Slco6C1 (mouse; Q3V161)
1.A.1.19.2	Sperm-associated cation channel, CatSper2 with 530 aas and 6 TMSs; it is a voltage-gated calcium channel that plays a central role in calcium-dependent physiological responses essential for successful fertilization, such as sperm hyperactivation, acrosome reaction and chemotaxis towards the oocyte (Strünker et al. 2011). The CatSper calcium channel is indirectly activated by extracellular progesterone and prostaglandins following the sequence: progesterone > PGF1-alpha = PGE1 > PGA1 > PGE2 >> PGD2 (Lishko et al. 2011).	Eukaryota	Metazoa, Chordata	CatSper2 of Homo sapiens (26051223)
1.A.1.19.3	Alkalinization-activated, Ca²⁺-selective cation channel of sperm 1, CatSper1, required for male fertility and the hyperactivated motility of spermatozoa. These channels require auxiliary subunits, CatSper β, γ and δ for activity (Chung et al., 2011; Liu et al., 2007).	Eukaryota	Metazoa, Chordata	CatSper of Mus musculus CatSper1 (Q91ZR5) CatSper3 (Q86XQ3) CatSper4 (Q8BVN3) CatSperβ (Q8C0R2) CatSperγ (C6KI89) CatSperδ (Tmem146) (E9Q9F6)
1.A.1.20.1	K⁺ voltage-gated ether-a-go-go-related channel, H-ERG (KCNH2; Erg; HErg; Erg1, Kv11.1) subunit K_v11.1 (long QT syndrome type 2) (Gong et al., 2006; Chartrand et al. 2010; McBride et al. 2013). Selective expression of HERG and Kv2 channels influences proliferation of uterine cancer cells (Suzuki and Takimoto 2004). H-ERG forms a heteromeric K⁺ channel regulating cardiac repolarization, neuronal firing frequency and neoplastic cell growth (Szabó et al., 2011). Oligomerization is due to N-terminal interactions between two splice variants, hERG1a and hERG1b (Phartiyal et al., 2007). Structure function relationships of ERG channel activation and inhibition have been reviewed (Durdagi et al., 2010). Interactions between the N-terminal domain and the transmembrane core modulate hERG K channel gating (Fernández-Trillo et al., 2011). The marine algal toxin azaspiracid is an open state blocker (Twiner et al., 2012). Verapamil blocks channel activity by binding to Y₆₅₂ and F₆₅₆ in TMS S₆ (Duan et al. 2007). Hydrophobic interactions between the voltage sensor and the channel domain mediate inactivation (Perry et al. 2013), but voltage sensing by the S4 segment can be transduced to the channel gate in the absence of physical continuity between the two modules (Lörinczi et al. 2015). Mutations give rise to long QT syndrome (Osterbur et al. 2015). Polyphenols such as caffeic acid, phenylethyl ester (CAPE) and curcumin inhibit by modification of gating, not by blocking the pore (Choi et al. 2013). Potassium ions can inhibit tumorigenesis through inducing apoptosis of hepatoma cells by upregulating potassium ion transport channel proteins HERG and VDAC1 (Xia et al. 2016). Incorrectly folded hERG can be degraded by Bag1-stimulated Trc-8-dependent proteolysis (Hantouche et al. 2016). The S1 helix regulates channel activity. Thus, S1 region mutations reduce both the action potential repolarizing current passed by Kv11.1 channels in cardiac myocytes, as well as the current passed in response to premature depolarizations that normally helps protect against the formation of ectopic beats (Phan et al. 2017). Interactions of beta1 integrins with hERG1 channels in cancer cells stimulate distinct signaling pathways that depended on the conformational state of hERG1 (Becchetti et al. 2017). ERG1 is sensitive to the alkaloid, ginsenoside 20(S) Rg3 which alters the gating of hERG1 channels by interacting with and stabilizing the voltage sensor domain in an activated state (Gardner et al. 2017). Channels split at the S4-S5 linker, at the intracellular S2-S3 loop, and at the extracellular S3-S4 loop are fully functional channel proteins (de la Peña et al. 2018). IKr is the rapidly activating component of the delayed rectifier potassium current, the ion current largely responsible for the repolarization of the cardiac action potential. Inherited forms of long QT syndrome (LQTS) in humans are linked to functional modifications in the Kv11.1 (hERG) ion channel and potentially life threatening arrhythmias. hERG1b affects the generation of the cardiac Ikr and plays an important role in cardiac electrophysiology (Perissinotti et al. 2018). X-ray crystallography and cryoEM have revealed features of the "nonswapped" transmembrane architecture, an "intrinsic ligand," and small hydrophobic pockets off a pore cavity. Drug block and inactivation mechanisms are discussed (Robertson and Morais-Cabral 2019). It forms a complex with β-integrin (TC#9.B.87.1.25) and NHE1 (TC# 2.A.36.1.13) (Iorio et al. 2020). Cardiotoxicity is caused mainly by the inhibition of human ether-a-go-go related gene (hERG) channel protein which leads to a life-threatening condition known as cardiac arrhythmia and is due to probable collapse of the pore. (Koulgi et al. 2021). Transmembrane hERG channel currents have been measured based on solvent-free lipid bilayer microarrays (Miyata et al. 2021). A computational method for identifying an optimal combination of existing drugs to repair the action potentials of SQT1 ventricular myocytes has been published (Jæger et al. 2021). Ginsenoside Rg3 may be a promising cardioprotective agent against vandetanib-induced QT interval prolongation through targeting hERG channels (Zhang et al. 2021). Insight has been obtained into the potassium currents of hERG (Guidelli 2023). Two novel KCNH2 mutations contribute to long QT syndrome (Owusu-Mensah et al. 2024). Channel activity is affected by moxifloxacin, terfenadine, arsenic, pentamidine, erythromycin, and sotalol (Goineau et al. 2024).	Eukaryota	Metazoa, Chordata	H-ERG of Homo sapiens (Q12809)
1.A.1.20.2	Erg2 (Kv11.2; KCNH6) K⁺ channel with slowly activating delayed rectifier (expressed only in the nervous system) (Shi et al., 1997). The human ortholog of 994 aas and 6 TMSs (Q9H252) is 86% identical to the rat protein. KCNH6 in humans and mice plays a key role in insulin secretion and glucose hemostasis (Yang et al. 2018).	Eukaryota	Metazoa, Chordata	Erg2 of Rattus norvegicus (O54853)
1.A.1.20.3	Erg3, Kv11.3, Eag3, KCNH7, K⁺ channel with a large transient current at positive potentials (expressed only in the nervous system) (Shi et al., 1997). Erg3-mediated suppression of neuronal intrinsic excitability prevents seizure generation (Xiao et al. 2018). The human ortholog (Q9NS40) is 1196 aas long with 6 TMSs and is 94% identical to the rat protein.	Eukaryota	Metazoa, Chordata	Erg3 of Rattus norvegicus (O54852)
1.A.1.20.4	K⁺ voltage-gated channel, rEAG1; K_v10.1; rat ether a go-go channel 1 (962 aas). Blocked by Cs⁺, Ba²⁺ and quinidine (Schwarzer et al., 2008). Cysteines control the N- and C-linker-dependent gating of KCNH1 potassium channels (Sahoo et al., 2012). The 3-d structure has been determined at 3.8 Å resolution using single-particle cryo-EM with calmodulin bound. The structure suggests a novel mechanism of voltage-dependent gating. Calmodulin binding closes the potassium pore (Whicher and MacKinnon 2016). Eag1 has three intracellular domains: PAS, C-linker, and CNBHD. Whicher and MacKinnon 2019 demonstrated that the Eag1 intracellular domains are not required for voltage-dependent gating but likely interact with the VS to modulate gating. Specific interactions between the PAS, CNBHD, and VS domains modulate voltage-dependent gating, and VS movement destabilizes these interactions to promote channel opening. Mutations affecting these interactions render Eag1 insensitive to calmodulin inhibition (Whicher and MacKinnon 2019). The structure of the calmodulin insensitive mutant in a pre-open conformation suggests that channel opening may occur through a rotation of the intracellular domains, and calmodulin may prevent this rotation by stabilizing interactions between the VS and the other intracellular domains. Intracellular domains likely play a similar modulatory role in voltage-dependent gating of the related Kv11-12 channels. The human ortholog, EAG or EAG-1, is 989 aas long and is 95% identical to the rat protein. In ether-a-go-go K⁺ channels, voltage-dependent activation is modulated by ion binding to a site located in an extracellular-facing crevice between transmembrane segments S2 and S3 in the voltage sensor. Silverman et al. 2004 found that acidic residues, D278 in S2 and D327 in S3, are able to coordinate a variety of divalent cations, including Mg²⁺, Mn²⁺, and Ni²⁺, which have qualitatively similar functional effects, but different half-maximal effective concentrations. EAG (ether-a-go-go) voltage-dependent K⁺channels with similarities and Differences in the structural organization and gating (Barros et al. 2020).	Eukaryota	Metazoa, Chordata	EAG1 of Rattus norvegicus (Q63472)
1.A.1.20.5	Potassium voltage-gated channel subfamily H member 3 (Brain-specific eag-like channel 1, BEC1) (Ether-a-go-go-like potassium channel 2) (ELK channel 2, ELK2) (Voltage-gated potassium channel subunit, Kv12.2). Deletion causes hippocampal hyperexcitability and epilepsy (Zhang et al. 2010). A selective inhibitor is ASP2905 (Takahashi et al. 2017). Voltage-sensor movements in the Eag Kv channel under an applied electric field have been measured (Mandala and MacKinnon 2022).	Eukaryota	Metazoa, Chordata	KCNH3 of Homo sapiens
1.A.1.20.6	Cyclic nucleotide-binding, voltage-gated, Mg²⁺-dependent, CaMKII-regulated K⁺ channel, Eag. Eag recruits CASK (TC# 9.B.106.3.2) to the plasma membrane; forms a heterotetramer (Liu et al. 2010). Phosphorylation is catalyzed by CaMKII (TC# 8.A.104.1.11)	Eukaryota	Metazoa, Arthropoda	Eag of Drosophila melanogaster
1.A.1.20.7	Cyclic nucleotide-gated K⁺ channel, CNGC or CNG1 of 894 aas and 6 TMSs (Wheeler and Brownlee 2008).		Viridiplantae, Chlorophyta	CNG1 of Chlamydomonas reinhardtii
1.A.1.20.9	Potassium voltage-gated channel subfamily H member 5 of 988 aas and 6 TMSs, EAG2 or KCNH5. This pore-forming α-subunit of voltage-gated potassium channel elicits a non-inactivating outward rectifying current. The channel properties may be modulated by cAMP and subunit assembly (Bauer and Schwarz 2018).	Eukaryota	Metazoa, Chordata	Eag2 of Homo sapiens
1.A.1.20.10	The KCNH1 K+ channel protein of 989 aas and 6 TMSs. Tian et al. 2023 expanded the phenotypic spectrum of KCNH1 and explored the correlations between epilepsy and molecular sub-regional locations. They found two novel missense variants of KCNH1 in three individuals with isolated FS/epilepsy. Variants caused a spectrum of epileptic disorders ranging from a benign form of genetic isolated epilepsy/FS to intractable form of epileptic encephalopathy. The genotypes and variant locations helped explain the phenotypic variation of patients with KCNH1 variants (Tian et al. 2023).	Eukaryota	Metazoa, Chordata	KCNH1 of Homo sapiens
1.A.1.21.1	K⁺- and Na⁺-conducting NaK channel, NaK2K of 97 aas and 2 TMSs. The 3-D structure has been solved with Na⁺ and K⁺bound (Shi et al., 2006). It exhibits tight structural and dynamic coupling between the selectivity filter and the channel scaffold (Brettmann et al. 2015). A hydrophobic residue at the bottom of the selectivity filter, Phe92, appears in dual conformations. One of the two conformations of Phe92 restricts the diameter of the exit pore around the selectivity filter, limiting ion flow through the channel, while the other conformation of Phe92 provides a larger-diameter exit pore from the selectivity filter. Thus, Phe92 acts as a hydrophobic gate (Langan et al. 2020).	Bacteria	Bacillota	NaK channel of Bacillus cereus (2AHYB) (Q81HW2)
1.A.1.21.2	Two pore domain potassium channel family protein of 122 aas and 2 TMSs.	Bacteria	Chloroflexota	K+ channel of Anaerolineales bacterium
1.A.1.21.3	Two pore domain potassium channel family protein of 140 aas and 2 TMSs.	Archaea	Euryarchaeota	K⁺ channel of Methanosarcina mazei
1.A.1.22.1	The cyclic nucleotide-gated K⁺ channel, MmaK. (Activated by cyclic AMP and cyclic GMP; inactivated at slightly acidic pH (Kuo et al., 2007))	Bacteria	Pseudomonadota	MmaK of Magnetospirillum magnetotacticum (Q2W0I8)
1.A.1.23.1	The pea symbiosis protein, essential for nodulation, mycorrhization, and Nod-factor-induced calcium spiking, SYM8 or DMI1 (Does not make infections 1). (Most similar to 1.A.1.13.2; 894aas; 4 TMSs between residues 136 and 339) (Edwards et al., 2007).	Eukaryota	Viridiplantae, Streptophyta	SYM8 of Pisum sativum (Q4VY51)
1.A.1.23.2	Root nuclear envelope CASTOR: homomeric ion channel (preference of cations such as K⁺ over anions) (Charpentier et al., 2008) (62% identical to 1.A.1.23.1).	Eukaryota	Viridiplantae, Streptophyta	CASTOR of Lotus japonicus (Q5H8A6)
1.A.1.23.3	POLLUX homomeric ion channel (preference for cations over anions) (Charpentier et al., 2008) (81% identical to 1.A.1.23.1).	Eukaryota	Viridiplantae, Streptophyta	POLLUX of Lotus japonicus (Q5H8A5)
1.A.1.23.4	putative ion channel (N-terminal domain) protein with C-terminal TrkA-N domain (DUF1012); NAD-binding lipoprotein.	Bacteria	Actinomycetota	Ion channel protein of Streptomyces coelicolor
1.A.1.24.1	The cyclic nucleotide regulated K⁺ channel, CNR-K⁺ channel (412 aas)	Bacteria	Pseudomonadota	CNR-K⁺ channel of Rhodopseudomonas palustris (Q02006)
1.A.1.24.2	K⁺ channel protein homologue	Bacteria	Myxococcota	K⁺ channels protein homologue of Stigmatella aurantiaca (Q08U57)
1.A.1.24.3	Putative 6 TMS potassium channel	Bacteria	Myxococcota	Potassium ion channel of Myxococcus xanthus
1.A.1.24.4	Putative K⁺ channel	Bacteria	Cyanobacteriota	K channel of Cyanotheca (Synechococcus) sp PCC8801
1.A.1.24.5	Cyclic nucleotide-gated K⁺ channel of 459 aas.	Bacteria	Pseudomonadota	Channel of Labenzia aggregata
1.A.1.24.6	Uncharacterized ion channel protein of 276 aas and 6 TMSs	Bacteria	Bacteroidota	UP of Flavobacterium psychrolimnae
1.A.1.25.1	The 6TMS bacterial cyclic nucleotide-regulated, voltage independent channel, MlotiK1 or MloK1 (Clayton et al., 2008). Gating involves large rearrangements of the cyclic nucleotide-binding domains (Mari et al., 2011). The electron crystalographic structure is available (PDB 4CHW) revealing ligand-induced structural changes (Schünke et al. 2011; Scherer et al. 2014; Kowal et al. 2014). Such changes may be lipid dependent (McCoy et al. 2014). High-speed atomic force microscopy has been used to measure millisecond to microsecond dynamics (Scherer et al. 2014; Kowal et al. 2014). Such changes may be lipid dependent (McCoy et al. 2014). High-speed atomic force microscopy has been used to measure millisecond to microsecond dynamics (Heath and Scheuring 2019).	Bacteria	Pseudomonadota	MlotiK1 of Mesorhizobium loti (Q98GN8)
1.A.1.26.1	The rodent malaria parasite K⁺ channel, PfKch1 (929aas) (Ellekvist et al., 2008).	Eukaryota	Apicomplexa	Kch1 of Plasmodium berghei (Q4YNK7)
1.A.1.26.2	Voltage-gated potassium channel, KCh1, of 1966 aas with 12 TMSs in a 2 (residues 50 - 100) + 10 (residues 550 - 900) TMS arrangement (Wunderlich 2022).	Eukaryota	Apicomplexa	KCh1 of Plasmodium falciparum
1.A.1.26.3	Uncharacterized protein of 1949 aas and 11 - 13 TMSs in a 2 + 8 - 10 +1 TMS arrangement (Wunderlich 2022).	Eukaryota	Apicomplexa	UP of Plasmodium falciparum
1.A.1.27.1	Putative 4 TMS ion channel protein. TMSs 1-2 may not be homologous to TMSs 3-4 which probably form the channel.	Bacteria	Actinomycetota	Hypothetic VIC family member of Streptomyces coelicolor
1.A.1.27.2	Putative 4 TMS potassium ion channel protein. TMSs 1-2 may not be homologous to TMSs 3-4 which probably form the channel.	Bacteria	Actinomycetota	Putative ion channel of Streptomyces coelicolor
1.A.1.27.3	Uncharacterized protein of 114 aas	Bacteria	Pseudomonadota	UP of Rhizobium meliloti
1.A.1.27.4	Uncharacterized protein of 148 aas and 3 or 4 TMSs	Bacteria	Pseudomonadota	UP of Marinobacter hydrocarbonoclasticus
1.A.1.28.1	Putative K⁺ channel	Bacteria	Pseudomonadota	Putative K⁺ channel of Klebsiella varicola (D3RJS6)
1.A.1.28.2	Putative K⁺ channel	Bacteria	Pseudomonadota	Putative K⁺ channel of Pseudomonas fluorescens (C3K1P0)
1.A.1.28.3	Thylakoid membrane 6 TMS voltage-sensitive K⁺ channel, SnyK; important for photosynthesis (Checchetto et al. 2012).	Bacteria	Cyanobacteriota	SynK of Synechocystis sp.
1.A.1.28.4	Putative voltage-dependent K⁺ channel	Bacteria	Pseudomonadota	K⁺ channel of Vibrio alginolyticus
1.A.1.28.5	Putative voltage-dependent K⁺ channel	Bacteria	Pseudomonadota	K⁺ channel of E. coli
1.A.1.28.6	Putative voltage-dependent K⁺ channel	Bacteria	Pseudomonadota	K⁺ channel of Acinetobacter baumannii
1.A.1.28.7	Uncharacterized protein of 228 aas and 6 TMSs	Archaea	Euryarchaeota	UP of Methanoculleus bourgensis (Methanogenium bourgense)
1.A.1.28.8	Two pore domain potassium channel family protein of 246 aas and 6 TMSs.	Bacteria	Planctomycetota	Putative K⁺ channel of Planctomycetes bacterium
1.A.1.29.1	The 2 - 4 TMS K⁺ channel, LctB (Wolters et al. 1999).	Bacteria	Bacillota	LctB of Bacillus stearothermophilus
1.A.1.29.2	Uncharacterized protein of 481 aas and 2 TMSs. (Pfam CL0030)	Archaea	Euryarchaeota	UP of Pyrococcus furiosus
1.A.1.29.3	Uncharacterized protein of 326 aas and 2 TMSs	Bacteria	Pseudomonadota	UP of Pseudoalteromonas luteoviolacea
1.A.1.29.4	C-terminal 2 TMS channel protein of 723 aas with 5 N-terminal pentapeptide repeats in a YjbI domain of unknown function	Archaea	Euryarchaeota	Channel protein of Natrinema altunense
1.A.1.29.5	Ion transport 2 domain-containing protein of 345 aas and 2 TMSs	Archaea	Euryarchaeota	Ion transport 2 domain-containing protein of Halococcus salifodinae
1.A.1.29.6	Putative cation transporting channel-2 of 288 aas with 2 N-terminal TMSs (Hug et al. 2016).	Bacteria	Candidatus Peregrinibacteria	Channel-2 of Candidatus Peribacter riflensis
1.A.1.29.7	Putative K⁺ channel of 317 aas and 2 TMSs with a central P-loop.	Archaea	Candidatus Woesearchaeota	K+ channel of Candidatus Woesearchaeota archaeon (marine sediment metagenome)
1.A.1.30.1	Uncharacterized putative chloride channel protein of 219 aas and 2 TMSs.	Viruses	Heunggongvirae, Uroviricota	UP of Vibrio phage 1.081.O._10N.286.52.C2