Figure 1. Proposed chain of residues involved in the voltage sensor selectivity filter gate (VS-SF) coupling.
(A) Schematic representation of residues involved in the VS-SF coupling. Voltage sensor domain (VSD) is depicted in blue, whereas pore domain (PD) is depicted in light purple. (B) Intramembrane view of the active state. (C) Intramembrane view of S4 in resting state and PD in active state. (D) Extracellular view of the active state S4 segment (blue ribbon) and PD (light purple ribbon) are from an adjacent subunit, based on a computational 3D model of crystallographic structures of KV1.2 (Chen et al., 2010) (Shaker-like channel, PDB: 3LUT). The model shows the VSD in the active/relaxed state for B and D. The S4 in the resting state is based on the consensus model (Vargas et al., 2011; Vargas et al., 2012). Residues proposed to be implicated in the VS-SF coupling mechanism are depicted by their van der Waals volumes (Carvalho-de-Souza and Bezanilla, 2019) (Shaker numbering): L361 (vermilion), L366 (black), L409 (green), S411 (blue), S412 (light purple), F433 (orange), W434 (yellow), and Y445 (sky blue). From the consensus model, it is possible to observe that L361 and L366 are practically in the same horizontal plane with the VS-SF coupling residues from the PD.