Comparison of S209F currents with and without KCNE1. (A) S209F+KCNE1 or (B) S209F without KCNE1 ionic currents were recorded at 35°C during 2-s depolarizing pulses to between −100 and +100 mV, followed by a 1-s repolarizing pulse to −50 mV. (C) g-V relationships from the peak tail currents. The V_1/2 of activation and slope factor was −39.0 ± 4.3 and 16.6 ± 2.3 for S209F and −31.0 ± 2.3 and 14.9 ± 1.2 for S209F+KCNE1. (D) Activation time constants (τ_act) from fits to currents (A and B) at each potential (S209F+KCNE1, n = 8; S209F alone, n = 5). Note that for S209F expressed alone, the cells were cultured at 30°C to rescue expression; coexpressing with KCNE1 allowed expression at a culture temperature of 37°C.