8.A.14.1.1
Sloβ auxiliary subunit; also called KCMNB4, of 210 aas and 2 TMSs, at the N- and C-termini (Behrens et al. 2000). It is 94% identical to the human ortholog and 100% identical to the rat ortholog. It is a regulatory subunit of the calcium activated potassium KCNMA1 (maxiK) channel as it modulates the calcium sensitivity and gating kinetics of KCNMA1 (Brenner et al. 2000). It decreases the gating kinetics and calcium sensitivity of the KCNMA1 channel, but with fast deactivation kinetics. It may also decrease KCNMA1 channel openings at low calcium concentrations but increases channel openings at high calcium concentrations (Ha et al. 2004). beta4 also makes the KCNMA1 channel resistant to 100 nM charybdotoxin (CTX) toxin concentrations (Meera et al. 2000). It's 3-d structure in complex with Slo1 shows it forms a tetramer on the periphery of Slo1 (see TC# 1.A.1.3.10; Tao and MacKinnon 2019).