(A) KCNQ1 currents from Xenopus oocytes recorded before (black) and after (blue) adding 1 µM ML277. The test voltages were from −120 mV to 80 mV with 20 mV increments, and then returned to −40 mV for measuring the tail currents. (B) 1 µM ML277 effects on KCNQ1 +KCNE1 channels with injected mRNA weight ratio of KCNQ1:KCNE1 = 300:1 (left, unsaturated KCNE1 binding) and 4:1 (right, saturated KCNE1 binding). The test voltages were 40 mV for 4 s, and then returned to −40 mV. (C) Activation time constants (τ) of KCNQ1 currents recorded at +40 mV before (black) and after (blue) adding ML277. The time constants of the fast component (τf) and slow component (τs) were 48 ± 3 ms and 0.60 ± 0.03 s for control, and 52 ± 3 ms and 0.99 ± 0.07 s for after adding ML277. The p values were 0.37 for τf, and 0.00091 for τs, t-test, n ≥ 4. (D) Averaged results of activation time constants (τf and τs) of KCNQ1 currents recorded at different voltages before (black) and after (blue) adding ML277. n ≥ 4. (E) The increased current by ML277 (IML277-IControl, Δ current) from panel A. The first 1 s activation currents were shown with insets of enlarged scales, and different colors were utilized to show the ‘delay’ of the increased currents at different voltages. (F–G) KCNQ1 currents recorded before (black) and after (blue) adding ML277 with 5 s time duration at −50 mV (F) and 100 ms time duration at +40 mV (G). The tail currents were recorded at −60 mV. Voltage protocols are shown on the top. All error bars in this and other figures are ± SEM.