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).