Click on image to view larger version.

Figure 5 Biophysical assay. (A) Whole-cell current recordings of wild-type (WT) and mutant sodium (Na) channels. Sodium channels were expressed with transient transfection in HEK293 cells in the presence of hß₁. Currents were recorded at various membrane potentials from –90 to +90 mV in 10-mV increments from a holding potential of –120 mV. No currents were detected in cells expressing each mutant. (B) Voltage dependence of steady-state inactivation and activation of mutant Na channels cotransfected with WT (mutant-hH₁ [or pRcCMV as a control to adjust the total amount of DNA]: WT-hH₁: hß₁ = 1:1:1). The curve was fit with the Boltzmann equation: I/I_max = [1+exp((V-V_1/2)/k)^–1]. (C) Current densities of mutant Na channels. Na currents were elicited at –30 mV from a holding potential of –120 mV. hH₁ = human cardiac Na channel -subunit.