Figure 3.

Relaxation of κ-PVIIA block of Shaker currents depends on the permeant cation, Rb⁺ or K⁺. (A) Ratios between toxin and control current traces from the IV experiments in Fig. 2 from IV protocols (V_H = −100 mV, V_P from −50 mV to +70 mV, every 20 mV) in different ionic conditions (symmetrical K⁺ with 200 nM κ-PVIIA, symmetrical Rb⁺ with 500 nM, K_ext/Rb_int with 300 nM, and Rb_ext/K_int with 400 nM). (B) Semilogarithmic plot of the mean values ± SD of the dissociation constants (K^O) versus test potential for symmetrical K⁺ (empty squares) or symmetrical Rb⁺ (filled squares). The continuous lines correspond to the exponential fit with K^O(V) = K^O (0)*exp(−V/vs), with K^O = 146 nM at 0 mV and vs = 43 mV for symmetrical K⁺ and 1023 nM and vs = 76 mV for symmetrical Rb⁺. (C) K^O versus Vp for K_ext/Rb_int and Rb_ext/K_int together with the fits from B.