Slow gating charge recovery of WT and F380A. (A) Representative recording of gating currents evoked by 200-mV pulses with different durations from 0.04 to 120 ms. (B and C) Slow gating charge kinetics of BK and BK-F380A. The OFF charge (Q_OFF; filled circles; mean ± SEM) was integrated in a range of 1 ms, normalized to the Q_MAX for each patch, and plotted against the pulse duration (time; logarithmic scale) for different voltage steps (40, 80, 120, 160, and 200 mV). The Q_OFF/Q_MAX − t relations were fitted with a two-component exponential function (solid line) with time constant and amplitude of the fast component constrained to the exponential fit of I_gON at these voltages. (D and E) 10-state allosteric model proposed for WT and mutant F380A channel, respectively. Darkness of the arrows indicates the probability of transitions.