FIGURE 5.

An allosteric model of BK channel activation. The schematic representation of the model includes a pore domain and three regulatory domains: the VSD and two Ca²⁺-sensing domains (RCK1 and RCK2) per subunit. Intrinsic gating between closed (C) and open (O) states of the pore domain is specified by the voltage-dependent equilibrium constant L; the VSD can be found either in the resting (R) or active (A) state according to equilibrium constant J; Ca²⁺ sensors can exist in unbound or Ca²⁺-bound states according to equilibrium constants K₁ and K₂. D, C₁, C₂, E₁, E₂, and F are allosteric factors (see supplemental data).