Fig. 4.
The Q-V and G-V curves were well fitted to the empirical equation accounting for the ΔpH-dependent shifts. The normalized charge or conductance was globally fitted using a least-squares minimization method to the empirical equation 1/{1 + exp[(ΔG0 − 2.3εRTΔpH − zFV)/RT]} (Eq. 6). (A) Q-V curves of the monomeric D160N Hv1 mutant at different ΔpHs shown in Fig. 3D were globally fitted to Eq. 6. The lines are the curves obtained from the fit at the indicated ΔpH using the parameters ΔG0 = 12.3 ± 0.3 kJ/mol, ε = 0.57 ± 0.02, and z = 0.91 ± 0.02. (B) G-V curves of the monomeric Hv1 at different ΔpHs shown in Fig. 1D were globally fitted to Eq. 6. The lines are the curves obtained from the fit at the indicated ΔpH using the parameters ΔG0 = 8.9 ± 0.1 kJ/mol, ε = 0.51 ± 0.01, and z = 0.75 ± 0.01. V0.5 and V0 values calculated from the global fit parameters using Eq. 11 are listed in SI Appendix, Table S3.