Figure 1. Voltage dependence of activation and fast inactivation kinetics for wild-type and Ile693Thr mutant Na⁺ channel recorded in 3 mm (A-C) or 30 mm (D-F) external K⁺.

A and D, representative traces of wild-type and Ile693Thr mutant channels elicited at two different command potentials as indicated below the traces. Note the lower threshold for mutant channel activation than for wild-type. B and E, normalized current-voltage relationships obtained from HEK 293 cells expressing either wild-type (○, n = 7 and n = 5 in B and E, respectively) or Ile693Thr mutant channels (•, n = 8 and n = 5 in B and E, respectively); data are expressed as means ±s.e.m. C and F, voltage dependence of the fast inactivation time constant for wild-type (^) and mutant channels (•); data shown in C and F were respectively computed from the same recordings as those used in B and E.