Fig. 1
Time and voltage dependence of KCNQ1 hook currents. a Left, representative KCNQ1 fast decay current recorded in ND96 solution from a triple pulse protocol. The hyperpolarizing pulse was for 20 ms at −120 mV, and the depolarizing pulse was to +40 mV. The inset shows the fast decaying currents in response to the return of the voltage to +40 mV after hyperpolarization, with expanded current and time scales. Right, representative KCNQ1 + KCNE1 current recorded under the same conditions. b Left, time dependence of KCNQ1 hook currents recorded in high potassium (100 mM K+) solution. The pre-pulses were +40 mV with time durations ranging between 0.02 and 4.355 s, and the test pulse was 2 s long at −120 mV. The inset shows the hook in tail currents with an expanded time scale. Right, representative KCNQ1 + KCNE1 current recorded under the same conditions. c Voltage dependence of KCNQ1 hook currents recorded in high potassium (100 K+) solution. The pre-pulse was 4 s with voltages ranging from −80 to +60 mV, and the test pulse was 2 s at −120 mV. The inset shows tail currents with an expanded time scale. d KCNQ1 hook current (black) fitted with the double exponential function F(t) = A 1 × exp(−t/τ 1) + A 2 × exp(−t/τ2) + C. The fitting curve, slow component (A 1 × exp(−t/τ 1) + C), and hook component (A 2 × exp(−t/τ 2)) are shown in red, cyan, and blue, respectively. e Normalized A 1 (top) and A 2 (bottom) of KCNQ1 hook currents vs. time durations of the pre-pulse, with voltages ranging from −60 to +60 mV (n ≥ 4). Error bars are SEM
