Fig. 1: The CBD-bound KCNQ2-CaM structure (KCNQ2-CaM_CBD).

a The 3D reconstruction and the cartoon model of KCNQ2-CaM_CBD. b The density maps of two CBD molecules in different orientations at the contour level of 3.6 σ. c Interactions between CBD_A and KCNQ2. The dashed lines indicate hydrogen bonds. d Interactions between CBD_B and KCNQ2. The dashed lines indicate hydrogen bonds. e Representative traces of KCNQ2 currents in the absence (black) and presence of 10 μM CBD (red) or 100 nM HN37 (blue). (Inset) The recording protocol. The cell was clamped at −80 mV and the KCNQ2 currents were elicited by a depolarizing voltage step of −40 mV for 1500 ms, followed by a hyperpolarizing step to −120 mV for 500 ms. f The dose-response curve of CBD on the current amplitude of KCNQ2 at −40 mV. Data are presented as mean ± SEM; n = 3 (0.1 μM), 3 (1 μM), 5 (3 μM), 5 (10 μM), and 3 (30 μM) individual cells. g Voltage-dependent activation curves of KCNQ2 before (black) and after (red) application of 10 μM CBD. Data are presented as mean ± SEM; n = 5 individual cells. h The half maximal activation voltage shift (ΔV_1/2) of WT KCNQ2 and mutants by 10 μM CBD. Data are presented as mean ± SEM. An unpaired two-tailed t test was performed to compare WT and each mutant. **p = 0.0036 for F104A, *p = 0.0307 for W236A, **p = 0.0083 for L272A, and p = 0.3123 for T296A. For W236A, n = 3 individual cells; For WT and other mutants, n = 5 individual cells. i CBDs induce a rotamer change of Trp236 in S5. j Structural comparison of VSDs from KCNQ2-CaM_apo and KCNQ2-CaM_CBD when the whole channels are aligned. k The closed activation gate of KCNQ2-CaM_CBD. The dashed lines show diagonal atom-to-atom distance (in Å) at the constriction-lining residues Ser314 and Leu318. For (f–h), source data are provided in the Source Data file.