Fig. 3. Key residues involved in the E–M coupling when the VSD adopts the activated conformation.
a A cartoon scheme to illustrate that ML277 specifically enhances AO state E–M coupling27. b Currents of WT KV7.1 and W248R before and after adding 1 µM ML277. Voltage: +40 mV then returned to −40 mV. c 1 µM ML277-induced current increase on KV7.1 WT and with mutations in the VSD, S4-S5L, S5, and S6. The residues were mutated to alanine (A), tryptophan (W), or to known LQTS mutations. The dotted line shows 2X the standard error below the average current increase of WT KV7.1. Mutations that show ML277-induced current increases (mean + SEM) below the dotted line are labeled as red. N.C. mutations show little or no current. Inact. mutations show obvious c-type like inactivation5. Data points are shown in small open circles. d Current ratios of IIKs/IKv7.1 (black) and IE1R/R4E/IE1R/R2E (blue) for WT and mutant KV7.1. Star indicates LQTS-associated mutations. e V50 values of G–V, F1–V, and F2–V relations for WT and mutant KV7.1 channels. Data points are shown in small open circles. f Current ratios of IIKs/IKv7.1 (black) and IE1R/R4E/IE1R/R2E (blue) for WT and the S4c mutant channels. g V50 values of G–V, F1–V, and F2–V relations for WT and S4c mutant channels. Data points are shown in small open circles. h Mapping the residues key to E–M coupling for AO state onto the KV7.1 cryoEM structure2. Only part of two adjacent subunits are shown. Yellow marks the residues in the charge transfer center (CTC) F167 (F0), E170, and D202. S1–S3 are transparent in the inset for clarity. Cyan: the four residues at the S4c, the fifth gating charge H5 (without showing the surface) is in the CTC when the S4c adopts the activated conformation2; blue: the thirteen residues from the ML277-screening. Pink shows eight residues from the neighboring subunit S5' and S6' from the ML277-screening. All averaged data are shown in mean±SEM. Source data are provided as a Source Data file.