Fig. 4.

Gating of α₀β channels. Patches containing BK channels formed by co-expressing both α₀and β (henceforth referred to as α₀β) were subject to voltage protocols as in Figure 3. A, Currents across the patch exposed to 5 μm Ca²⁺ for activation voltages ranging from −100 to +100 mV (steps of 10 mV). Tail currents were measured at −100 mV. B,G–V relationships obtained at four different calcium concentrations (1, 5, 25, and 50 μm) were fit with Boltzmann functions described in Equation 1. Notice that α₀β activates at more negative voltages than does α alone, and increasing the calcium concentration causes a greater leftward shift in the activation curve for α₀β.