Charge movement and fluorescence signals arise from the same conformational changes. (A and B) Gating current and fluorescence recordings are shown in the same time scale (enlarged view in B). Note that VSD-I barely activates during the time course of gating current measurements (10 ms). (C) Mean voltage dependence of charge movement (Q(V)), channel activation (G(V)), and individual VSD activations (F(V)) are shown. For clarity, only Boltzmann distributions describing G(V) and F(V) datasets are plotted (data points were already presented in Fig. S1 C and Fig. 3 C, respectively). The sum of F(V) curves weighed by their respective valence (pink diamonds) resembles the voltage dependence of the mean Q(V) curve (black circles; SEM bars are within the symbols, when not visible, n = 5).