FIGURE 1. Activation of SkM1 and SCN5A in HEK293 cells.

(A) Expression of SkM1 or SCN5A in HEK293 cells. Na⁺ currents were recorded in low Na⁺ (15 mM) Tyrode’s solution at room temperature. Cells were held at -100 mV and then pulsed to test potentials from -80 mV to +40 mV, with a 5 mV increment. (B) Current-voltage relationship of SkM1 (n=8) and SCN5A (n=10) in HEK293 cells. Data are normalized to the maximum peak current (mean±SE). (C), (D) Study of the m gates of SkM1 and SCN5A. Data of m³ are normalized to the maximal value and fitted to the equation $\mathrm{f}=\frac{1}{1+\exp [-(\mathit{Em}-\mathit{Vh})/K]}$, giving a midpoint of -21.1±0.5 mV and a slope of 5.9±0.4 mV (mean±SE, n = 8) for SkM1 (C), and a midpoint of -39.0±0.4 mV and a slope of 3.6±0.4 mV (mean±SE, n = 10) for SCN5A (D). The m curves were calculated from the curve fit.