Mutation of I696 to hydrophobic amino acids affects voltage sensing and the energetics of channel gating. (A) Normalized g-V relationships for I696X voltage-responsive mutants. Solid lines depict the best fit to a Boltzmann distribution to obtain the V_0.5 and z_g values. (B) V_0.5 values of the different I696X mutants obtained from the g-V curves. (C) z_g values of the different I696X mutants obtained from the g-V curves. (D) ΔG_o values at 0 mV for the I696X obtained considering a simple two-state model between a closed and an open state. g-V curves were normalized with respect to the true g_max of the channel obtained in the presence of 100 µM capsaicin (Table 1). Data are given as mean ± SEM (error bars), with n (number of cells) ≥ 5. *, P < 0.05 as compared with wild type, using the nonparametric Wilcoxon test.