Fig. 1

K525N&F627Y is a hyperpolarization-activated channel. a Representative currents of WT hERG overexpressed in CHO cells. The step voltage protocol (below) varies from -60 to +60 mV with a holding potential of -90 mV. The green arrow and red arrowhead indicate the measurement region of outward currents and tail currents, respectively. The 0 pA is indicated by a dashed line. b The normalized current-voltage (I-V) curve of WT hERG (n≥6) and F627Y (n≥6). Measured currents are indicated by the green arrow in Fig. 1a. c The normalized conductance-voltage (G-V) curve of WT hERG (n≥6). Measured currents are indicated by the red arrowhead in Fig. 1a. d Diagram of an hERG channel subunit that can be divided into a VSD (S1-S4) and a PD (S5-S6). K525 in the S4 helix and F627 in the selective filter is indicated by a red and purple star, respectively. The potential interacting residues (F431, C566, I607, and Y611) are also labelled with black dots. F431 is in S1, C566 is in S5, I607 and Y611 are in the pore helix. e Representative currents of F627Y. Step voltage protocol (below) varies from -165 to +30 mV with a holding potential at -70 mV. f Representative currents of K525N&F627Y. Step voltage protocol (below) varies from -130 to +30 mV with a holding potential at -70 mV. g The normalized I-V curve (n≥6) and h The normalized G-V curve (n≥6) of K525N&F627Y. i V_1/2 values of WT hERG and K525N&F627Y (n=12). Error bars represent mean ± SEM