Fig. 1: Classic interactions are necessary for E–M coupling when the VSD transitions into the intermediate state.
From: Two-stage electro–mechanical coupling of a KV channel in voltage-dependent activation
a VCF recordings of pseudo-WT KV7.1* (KV7.1-C214A/G219C/C331A). KV7.1+KCNE1 currents are shown at the same scale. The F–V relationships (blue circles) are fitted with a double Boltzmann function. F1–V represents the VSD transition from resting to intermediate state; F2–V represents the VSD transition from the intermediate to activated state. G-V represents channel opening with VSD transition at both the intermediate (IO) and the activated (AO) states. b Cartoon scheme illustrating the gating mechanism of two-step VSD movements and distinct two open states. c VCF recordings of V254M in KV7.1*. V254M+KCNE1 currents are shown at the same scales. The F–V relationships of KV7.1* and V254M are shown in gray and blue, respectively. d Cartoon scheme illustrating that V254M disrupts E–M couplings for both IO and AO. e Summary of data for WT and mutant KV7.1. VSD activation (blue, percentage change in fluorescence) and pore opening (black, current amplitude) are normalized to the WT. n ≥ 3. Blank: cells not injected with channel mRNA. Data points are shown in small open circles. f V50 values for the F1–V and F2–V. n ≥ 3. Data points are shown in small open circles. g Western blot results showing the membrane (top) and total (middle) expression of some mutants that eliminated both fluorescence and ionic currents. Gβ (bottom) from total protein is shown as negative control. WT KV7.1, H258W, and P343A are shown as positive controls. h Mapping the key residues V254, H258, A341, P343, and G345 (green) onto the S4-S5L/S6c interface in the KV7.1 cryoEM structure (PDB: 5VMS)2. All averaged data are shown in mean±SEM. Source data are provided as a Source Data file.
