Potassium Large Conductance Calcium Activated Channel Subfamily M Beta 4 (KCNMb4)

Sequence analysis predicted that the 210-amino acid KCNMB4 protein contains 2 conserved transmembrane domains and an extracellular domain containing an N-glycosylation site and 4 cys residues; however, like KCNMB3, KCNMB4 lacks the putative charybdotoxin/iberiotoxin-binding site.

Functional analysis of the effects of KCNMB4 on KCNMA1 showed that KCNMB4 slows activation kinetics, leads to steeper calcium sensitivity, and shifts the voltage range of BK current activation to more negative potentials than does KCNMB1. KCNMA1/KCNMB4 channels were not blocked by charybdotoxin or iberiotoxin and were activated by 17-beta-estradiol .