The voltage dependence of gating charge movement correlates to the voltage dependence of fast inactivation but not conductance. (A) Midpoint of the GV relationship for residue 1784 mutants plotted versus the midpoint of the QV relationship (n = 4–10). (B) Midpoint of the voltage dependence of fast inactivation for residue 1784 mutants plotted versus the midpoint of the QV relationship (n = 4–9). (C) Midpoint of the GV relationship for residue 1784 mutants plotted versus the time constant of open state fast inactivation at −10 mV (n = 4–10). (D) Fraction of maximal conductance blocked by decreasing extracellular pH to pH 6.0 for residue 1784 mutants plotted versus the time constant of closed-state inactivation onset at −50 mV (n = 3–10).