Conductance-voltage relationships of wild-type Nav1.2 and mutant channels in the presence of 200 nm Css IV with a 1-ms prepulse to +50 mV that preceded the test pulse by 60 ms. a, Nav1.2, V484A, and L849C. b, Nav1.2, F852A, and L855C. c, Nav1.2, L854C/PRE with a prepulse, and L854C/NP without a prepulse. d, Nav1.2, V857C, F858C, and L860C.