Figure 1. Schematic structure of β1 subunit-containing BK channel.

Cartoon showing a slo1-β1 subunit heterodimer. The channel-forming slo1 subunit includes transmembrane (TM) segments S0-S6 and intracellular Regulatory of Conductance for K⁺ (RCK) domains, these domains including distinct residues that participate in sensing changes in Ca²⁺ _i. Four slo1 monomers assemble to render fully functional BK channels. All four types of β subunits identified so far contain a similar design that includes intracellular N- and C-terminals, two transmembrane domains (TM1 and TM2), and an EC loop. EC and IC correspond to the extracellular and intracellular sides of the membrane.