Effects of E119/E^1.58 mutations on potency for Zn²⁺ modulation of Hv1 gating. (A) Representative currents in a cell expressing Hv1 E119A or E119H elicited by the indicated voltage protocol are shown in the absence (Control) or presence of the indicated [Zn²⁺]. (B) Normalized G_STEP-V relations are shown for representative cells expressing WT Hv1 (data from Fig. 2B), E119A, or E119H. Colored lines represent fits of the mean data to a Boltzmann function: WT Hv1 (dashed black line, V_0.5 = 61.9 mV, dx = 23.6), E119A (aqua line, V_0.5 = 98.5 mV, dx = 17.8), and E119H (orange line, V_0.5 = 92.4 mV, dx = 15.8). (C) Normalized Zn²⁺ concentration responses are shown for representative cells expressing E119A or E119H. Colored lines represent fits of the mean data to a Hill function: E119A (solid aqua line, IC₅₀ = 6.7 µM, n_H = 0.8) and E119H (solid orange line, IC₅₀ = 0.60 µM, n_H = 0.9). Dashed lines represent fits to WT Hv1, H140A, H193A, and H140A-H193A data, as shown in Fig. 2. Data points represent means ± SEM.