Figure 7.

Switching sequence differences in AC region between mSlo1 and dSlo1 either singly or in combination does not switch Ca²⁺ sensitivity of BK_Ca gating. (A) Steady-state G-V relations of m[d-Motif2] and m[d-Motif3]. Dotted lines are G-V relations of mSlo1. Parameters of the Boltzmann fits (solid lines): for m[d-Motif2], at 0 [Ca²⁺]_i, V_1/2 = 195.7 mV, z = 1.1; at 100 μM [Ca²⁺]_i, V_1/2 = 8.2 mV, z = 1.2; for m[d-Motif3], at 0 [Ca²⁺]_i, V_1/2 = 213.2 mV, z = 1.1; at 100 μM [Ca²⁺]_i, V_1/2 = 9.2 mV, z = 1.2. (B) Steady-state G-V relations of m[d-Motif12] and m[d-Motif13]. Dotted lines are G-V relations of mSlo1. Parameters of the Boltzmann fits (solid lines): for m[d-Motif12], at 0 [Ca²⁺]_i, V_1/2 = 186.5 mV, z = 1.2; at 100 μM [Ca²⁺]_i, V_1/2 = 22.2 mV, z = 1.1; for m[d-Motif13], at 0 [Ca²⁺]_i, V_1/2 = 211.9 mV, z = 1.4; at 100 μM [Ca²⁺]_i, V_1/2 = 38.4 mV, z = 1.3. (C) Free energy of activation provided by Ca²⁺ binding for the chimeric channels. Free energy change for each channel was in response to [Ca²⁺]_i change shown in parentheses for mSlo1 plotted alongside each group.