TCDB is operated by the Saier Lab Bioinformatics Group
TCIDNameDomainKingdom/PhylumProtein(s)
*1.A.62.1.1









The homotrimeric monovalent cation channel, TRIC-A (Mitsugumin-33A; 298 aas; 3-6TMSs; DUF714 domain) (Yazawa et al., 2007). PK+:Na+ = 1.5; impermeable to divalent cations.
Eukaryota
Metazoa
TRIC-A of Mus musculus (Q3TMP8)
*1.A.62.1.2









The homotrimeric monovalent cation channel, TRIC-B (TMEM38B; Mitsugumin-33B; 292 aas; 7 TMSs; DUF714 domain) (Yazawa et al., 2007). PK+:Na+ = 1.5; impermeable to divalent cations. Apparent subconductance openings provide most of the K+ flux when the SR membrane potential is close to zero (Matyjaszkiewicz et al. 2015).  Mutations give rise to osteogenesis imperfecta (OI) in humans, a group of clinically and genetically heterogeneous disorders characterized by decreased bone mass and recurrent bone fractures (Lv et al. 2016).

Eukaryota
Metazoa
TRIC-B of Mus musculus (Q9DAV9)
*1.A.62.1.3









TMEM38B/TRIC-B of 291 aas and 6 TMSs.  Monovalent cation channel required for maintenance of rapid intracellular calcium release. May act as a potassium counter-ion channel that functions in synchrony with calcium release from intracellular stores.  Required for intracellular homeostasis and is responsible for a mild form of recessive osteogenesis imperfecta. TRIC-B is proposed to counterbalance IP3R-mediated Ca2+ release from intracellular stores (Cabral et al. 2016).

Eukaryota
Metazoa
TRIC-B of Homo sapiens
*1.A.62.1.4









TRICB1 and TRICB2 of 313 aas and 295 aas, respectively. Yang et al. 2016 presented the structures of TRIC-B1 and TRIC-B2 channels from Caenorhabditis elegans in complex with endogenous phosphatidylinositol-4,5-biphosphate (PtdIns(4,5)P2, also known as PIP2) lipid molecules. The TRIC-B1/B2 proteins and PIP2 assemble into a symmetrical homotrimeric complex. Each monomer contains an hourglass-shaped hydrophilic por within a seven-transmembrane-helix domain. Structural and functional analyses revealed the central role of PIP2 in stabilizing the cytoplasmic gate of the ion permeation pathway and showed a marked Ca2+-induced conformational change in a cytoplasmic loop above the gate. A mechanistic model was proposed to account for the complex gating mechanism of TRIC channels (Yang et al. 2016).

Eukaryota
Metazoa
TRICB1/B2 of Caenorhabditis elegans
*1.A.62.2.1









Bacterial TRIC family homologue

Bacteria
Bacteroidetes/Chlorobi group
TRIC homologue of Gramella forsetii (A0M015)
*1.A.62.2.2









Uncharacterized protein of 204 aas and 7 TMSs.

Bacteria
Proteobacteria
UP of Yersinia pestis
*1.A.62.2.3









Uncharacterized protein, YicG, of 205 aas and 7 TMSs.

Bacteria
Proteobacteria
YicG of E. coli
*1.A.62.2.4









TRIC family homologue of 213 aas and 7 TMSs; it's high resolution 3-d structure is known (PDB# 5H36). TRIC channels are implicated in Ca2+ signaling and homeostasis. Kasuya et al. 2016 presented crystal structures of two prokaryotic TRIC channels in the closed state and conducted structure-based functional analyses of these channels. Each trimer subunit consists of seven TMSs with two inverted 3 TMS repeats (Silverio and Saier 2011). The electrophysiological, biochemical and biophysical analyses revealed that TRIC channels possess an ion-conducting pore within each subunit, and that trimer formation contributes to the stability of the protein. The symmetrically related TMS2 and TMS5 helices are kinked at conserved glycine clusters, and these kinks are important for channel activity. The kinks in TMS2 and TMS5 generate lateral fenestrations at each subunit interface that are occupied by lipid molecules (Kasuya et al. 2016).

Bacteria
Proteobacteria
TRIC channel of Rhodobacter spheroides
*1.A.62.3.1









Archaeal TRIC family homologue of 205 aas and 7 TMSs.  In animals, Ca2+ release from the sarcoplasmic reticulum (SR) or endoplasmic reticulum (ER) is crucial for muscle contraction, cell growth, apoptosis, learning and memory. The eukaryotic TRIC channels are cation channels balancing the SR and ER membrane potentials, and are implicated in Ca2+ signaling and homeostasis. Kasuya et al. 2016 presented crystal structures of two prokaryotic TRIC channels in the closed state and conducted structure-based functional analyses of these channels. Each trimer subunit consists of seven TMSs with two inverted 3 TMS repeats (Silverio and Saier 2011). The electrophysiological, biochemical and biophysical analyses revealed that TRIC channels possess an ion-conducting pore within each subunit, and that trimer formation contributes to the stability of the protein. The symmetrically related TMS2 and TMS5 helices are kinked at conserved glycine clusters, and these kinks are important for channel activity. The kinks in TMS2 and TMS5 generate lateral fenestrations at each subunit interface that are occupied by lipid molecules (Kasuya et al. 2016).  TRIC channels are involved in K+ uptake in prokaryotes, and have ion-conducting pores contained within each monomer. In a 2.2-Å resolution K+-bound structure, ion/water densities have been resolved inside the pore (PDB# 5H35) (Su et al. 2017). At the central region, a filter-like structure is shaped by the kinks on the second and fifth transmembrane helices and two nearby phenylalanine residues. Below the filter, the cytoplasmic vestibule is occluded by a plug-like motif attached to an array of pore-lining charged residues (Kasuya et al. 2016). The asymmetric filter-like structure at the pore center of SsTRIC may serve as a basis for the channel to bind and select monovalent cations, K+ and Na+ (Ou et al. 2017).

Archaea
Crenarchaeota
TRIC homologue of Sulfolobus solfataricus (Q981D4)
*1.A.62.3.2









UPF0126 of 7 TMSs. Adjacent to genes encoding a putative oligopeptide ABC uptake permease that controls sporulation and actinorhodin production (TC#3.A.1.5.34) (Shin et al. 2007).

Bacteria
Actinobacteria
UPF0126 of Streptomyces coelicolor (Q9RKM3)
*1.A.62.4.1









Putative TRIC channel protein

Eukaryota
Bangiophyceae
Putative TRIC channel of Galdieria sulphuraria
*1.A.62.4.2









Putative TRIC channel protein

Eukaryota
Blastocystis
Putative TRIC channel of Blastocystis hominis
*1.A.62.4.3









Putative TRIC channel protein

Eukaryota
Longamoebia
Putative TRIC channel protein of Acanthamoeba castellanii