Atomistic mechanism of noncanonical voltage gating in K_2P channels

In classical voltage-gated cation channels, the movement of a voltage-sensing domain (VSD) opens a gate in the pore domain. However, two-pore domain K⁺ (K_2P) channels lack a VSD and instead rely on K⁺ movement within the selectivity filter (SF) to convert voltage changes into pore opening. To uncover the atomistic basis of voltage gating in TREK K_2P channels, we integrated large-scale atomistic molecular dynamics simulations with extensive mutagenesis and patch-clamp electrophysiology, including sucrose-based experiments. Simulations revealed an asymmetric stability difference along the SF that results in a water-permeable extracellular side and a watertight intracellular side. Inactivation during inward flux occurs when water penetrates into the inner binding site and halts ion permeation, followed by the unbinding of three K⁺ ions, consistent with gating charge analysis. Our findings provide unprecedented atomistic insights into the C-type inactivation of TREK K_2P channels and establish a framework for investigating noncanonical voltage gating mechanisms in other ion channels.