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. 2011 Jul 27;286(38):33641–33651. doi: 10.1074/jbc.M111.282509

FIGURE 5.

FIGURE 5.

Voltage sensor trapping activity of CssIVE15A on V843A and E844N mutant channels. A, I-V plots obtained in the absence of toxin for WT rNav1.2a channels (circles) and V843A mutant channels (triangles). B, I-V plots for V843A mutant channels in the presence of 500 nm CssIVE15A with (filled triangles, +Pre) or without (open triangles, −Pre) a +50-mV, 1-ms prepulse applied 60 ms earlier. Inset, IVST traces recorded in the presence of 500 nm CssIVE15A with a 15-ms test pulse to −60 mV in the absence or presence of the prepulse. The solid lines are global fits to I-V curves with and without prepulses with parameters Va1 = −21.1 mV, k1 = −7.9 mV, Va2 = −59.5 mV, k2 = −8.2 mV. Without a prepulse, no current activated with the more negative voltage dependence. With a prepulse, 43.2% of the conductance activated with the negative voltage dependence. The line without symbols is the toxin-free data for V843A from panel A. C, I-V plots obtained in the absence of toxin for WT rNav1.2a channels (circles) and E844N mutant channels (squares). D, I-V plots for E844N mutant channels in the presence of 500 nm CssIVE15A with (filled squares, +Pre) or without (open squares, −Pre) the prepulse. Inset, IVST traces recorded in the presence of 500 nm CssIVE15A with a test pulse depolarizing to −60 mV for 15 ms in the absence or presence of a +50-mV, 1-ms prepulse 60 ms earlier. The solid lines are global fits to I-V curves with and without prepulses with parameters Va1 = 23.3 mV, k1 = −7.0 mV, Va2 = −60.7 mV, k2 = −8.1 mV. Without a prepulse, no current was activated with the more negative voltage dependence. With a prepulse, 43.2% of the conductance activated with the negative voltage dependence. The line without symbols is the toxin-free data for E844N from panel C. E, concentration-response curves for normalized IVST of V843A (open triangles) and E844N (open squares) mutant channels by CssIVE15A with the prepulse. IVST values were normalized to the current at the peak of the I-V curves for the corresponding mutants in the absence of toxin. The concentration-response data were fit with first-order Hill equations (n ≥ 4).