F463 may interact with K525 and K538 to modulate activation gating. (A) Comparison of the mean G-V relationship for the F463W/K525R double mutation with those of the single mutants. (B) Comparison of the mean G-V relationships for the F463W/K538R double mutation with those of the single mutants. (C) Comparison of the G-V relationships for the F463W/R537K double mutation with those of the single mutants. Lines in A–C represent Boltzmann function descriptions of the data; n values and Boltzmann parameters are shown in Table 1. (D) Plot of the τ_act values against the electrochemical potential for activation for the channel constructs described in A and B. Data points represent mean ± SEM (error bars).