Effect of ATP on the gating of hClC-1 at pH 6.2. Top panel, macroscopic current recordings from an inside-out patch upon perfusion with control internal solution at pH 7.3 (A), pH 6.2 (B), solution at pH 6.2 with 1 mM ATP (C), and after washout (D). (E) Voltage dependence of the overall open probability obtained from the macroscopic currents in the top panel as described in Materials and methods. Symbols are: square, internal solution at pH 6.2; circle, solution at pH 6.2 with 1 mM ATP. Lines are fits of Eq. 1 with the following parameters: solution at pH 6.2, V_1/2 = −94 mV, P_min = 0.50; solution at pH 6.2 with 1 mM ATP, V_1/2 = −95 mV, P_min = 0.43. (F) Effect of ATP at pH 6.2 on the slow gating mechanism of hClC-1. Data are from the same patch and were obtained from tail currents preceded by a 200-μs pulse to 160 mV. Symbols are as in E. Lines are fits of Eq. 1 with the following parameters: solution at pH 6.2, V_1/2 = −98 mV, P_min = 0.74; solution at pH 6.2 with 1 mM ATP, V_1/2 = −93 mV, P_min = 0.74.