Regulatory subunit of the calcium activated potassium KCNMA1 (maxiK) channel. Modulates the calcium sensitivity and gating kinetics of KCNMA1, thereby contributing to KCNMA1 channel diversity. Acts as a negative regulator that confers rapid and complete inactivation of KCNMA1 channel complex. May participate in KCNMA1 inactivation in chromaffin cells of the adrenal gland or in hippocampal CA1 neurons.
Expressed in kidney, heart and brain. Highly expressed in ovary. Expressed at low level in other tissues.
Belongs to the KCNMB (TC 8.A.14.1) family. KCNMB2 subfamily.
The ball and chain domain mediates the inactivation of KCNMA1. It occludes the conduction pathway of KCNMA1 channels, and comprises the pore-blocking ball domain (residues 1-17) and the chain domain (residues 20-45) linking it to the transmembrane segment. The ball domain is made up of a flexible N-terminus anchored at a well ordered loop-helix motif. The chain domain consists of a 4-turn helix with an unfolded linker at its C-terminus.