FIGURE 7.
Binding affinity and voltage sensor-trapping activity of CssIVE15A in WT and mutant rNav1.2a channels. The ratio of the KD of CssIV binding to mutant channels to that of WT channels (KD(mut)/KD(WT), open bars) studied by Cèstele et al. (8, 9) or the IVST ratio for mutant channels studied functionally here (filled bars). For mutant channels that enhance voltage sensor trapping, the IVST ratio was defined as −1[IVST(WT)/IVST(mut)]. For mutant channels that reduce voltage sensor trapping, the IVST ratio was defined as IVST(WT)/IVST(mut). At some loci multiple mutants were studied and the data corresponding to each mutant and its corresponding label are color coded. For instance, E837Q, E837R, and E837C are plotted in black, green, and red, respectively, in the bar graph. Empty bars represent previously studied amino acid residues (8, 9), whereas the filled bars represent new residues whose function was analyzed in this paper.