R294H-D352H forms a lower affinity Zn²⁺ site but is still able to promote the activated conformational state. (A and B) Normalized G-V relationships from oocytes expressing (A) Kv1.2-R294H-D352H (n = 7) and (B) Kv1.2-D352H (n = 7) channels recorded in the absence (solid squares) and presence (open circles) of 1 μM Zn²⁺. (C) A plot of ΔV_1/2 versus Zn²⁺ concentration in oocytes expressing Kv1.2-R294H-D352H channels, where ΔV_1/2 is the difference between the fitted V_1/2 values obtained in the absence and presence of varying concentrations of Zn²⁺. The data were fitted with a hyperbolic function (solid curve) with a half-maximal concentration of 470 nM (n = 5–10).