Voltage sensor-trapping activity of CssIVE15A on A841N and L846A mutant channels. A and C, I-V plots in the absence of toxin; B and D, I-V plots in the presence of 500 nm CssIVE15A with or without a prepulse. A, WT rNav1.2a (open circles) and A841N (open squares). B, A841N, in the absence (open squares, −Pre) and presence (filled squares, +Pre) of the prepulse. C, WT rNav1.2a (open circles) and L846A (open triangles). D, L846A in the absence (open triangles, −Pre) and presence (filled triangles, +Pre) of the prepulse.