Identification of Gating Sensitive Residues in TREK-2

Abstract

TREK-2, a two-pore domain potassium (K2P) channel, is known to respond to a wide range of stimuli, such as pH, membrane tension, and binding of small ligands. Moreover, an “up” and a “down” x-ray crystallographic states have been resolved and it has been shown that the “up” state has higher ion conductance. However, molecular explanations for gating mechanisms and whether transitions between these two states play an important role in gating remain elusive. We initiate the study by free energy calculations with mutants of TREK-2 to predict how the conformational equilibrium between the “up” and the “down” states is shifted by mutations at the distal TM4 segment. We identify several mutants that exhibit a considerable shift towards the “up” state. Furthermore, additional free energy calculations suggest that the conformational shift is critically determined by the extent of steric clashes between two of the lower bundle helices. These findings shed light on the molecular roles of the identified gating sensitive residues in governing transitions between the two states, which potentially serve as a gating mechanism of TREK-1 and TREK-2 under different physiological conditions.