The gating curves in the wild-type (WT), G1715E, F1764R, and G1715E/F1764R (GEFR) mutant channels. The activation (left) and inactivation curves (right; inactivating pulse duration = 5 s) were documented by the protocols described in Materials and methods. The data for the wild-type channel are from Fig. 1 A and shown as gray symbols with gray lines. The activation curves are fits with a Boltzmann function with V_1/2 values (in mV) of −27.2, −17.5, and 4.9 and k values of 3.9, 5.9, and 6.4 for G1715E (n = 3), F1764R (n = 6), and GEFR (n = 7) mutant channels, respectively. The inactivation curves are fits with a Boltzmann function with V_1/2 values (in mV) of −54.2, −52.3, and −54.2 and k values of 4.3, 4.6, and 5.8 for G1715E (n = 6), F1764R (n = 8), and GEFR (n = 6) mutant channels, respectively.