G657C and N658C affect both activation and deactivation. (A) Conductance versus voltage relations for G657C and N658C. An empirical double Boltzmann relation was required to fit the curve for G657C (See Materials and methods). (B) Exemplar G657C and N658C currents evoked at +40 mV from a holding potential of −80 mV. (C) Voltage dependence of G657C and N658C activation time constants. (D) Exemplar deactivation traces at −100 mV after a pulse to +40 mV. (E) Average deactivation time constants versus voltage. (F) Closed-state homology model of the closed state shows G657 (blue) and N658 (red) located next to each other in the vestibule. (G) A view from the cytoplasm shows the side chains' proximity to one another. (H) Open-state homology model cross-sectional membrane view shows G657 and N658 at the level of the S4-S5 linker. (I) View of G657 and N658 from the cytoplasm in the closed state.