Figure 1.

BK channel structure. (A) Topology of the pore-forming Slo1 subunit, including VSD, PGD, and CTD. Charged residues in the VSD that are important for voltage sensing are highlighted in yellow. The CTD contains binding sites for Ca²⁺, Mg²⁺, and heme. (B) Schematic organization of functional domains in the tetrameric channel. S6 segments in the PDG are connected to the CTD gating ring through S6-RCK1 linkers.