Figure 1.

Structural domains in BK_Ca channels and regulatory subunits. (A) BK_Ca is composed by 7 transmembrane domains (S0–S7) and a long intracellular C-terminus. S0–S4 form the voltage sensing domain, and S5–S6 conform the pore-gating domain. Ca²⁺ biding sites are highlighted in the Regulator of Potassium Conductance (RCK) 1 and RCK2 domains. A C-terminal 50 amino acid splice insert, DEC, is highlighted. (B) Regulatory BK_Ca subunits. Homotetramer model of the pore-forming α subunit, the two spanning domain regulatory β subunits (1–4), and single spanning domain γ (1–4) subunits. The loop of β4 subunit confers to BK_Ca α subunit its resistance to toxin inhibition (Meera et al., 2000).