The Membrane-Bound State of K_2P Potassium Channels

Potassium channel subunits composed of two-pore domains arranged in tandem (K2P) are of paramount importance for neural function. A variety of stimuli, such as membrane depolarization and tension, acidification, and anesthetic action, activate K2P channels. Most of the channel sensitivity is attributed to its intracellular C-terminal moiety, which works as a sensor domain required for proper integration of the electrical, chemical, and mechanical signals into channel activity. Herein, the structure of K2P in a membrane environment has been studied using molecular dynamics (MD). Two distinct fully atomistic models for the most studied K2P channel, namely, the TWIK-related (TREK)-1 channel have been built. These constructs were then inserted into a fully hydrated zwitterionic lipid bilayer, and each relaxed by means of MD simulations spanning ∼0.3 μs. Both simulated TREK-1 structures converged to a final conformation characterized by a closed pore and a C-terminal domain adsorbed onto the lipid bilayer surface. The C-terminus, which is physically linked to the pore and energetically coupled to the bilayer, is poised to gate the channel in response to membrane stimulation. The present study indicates the nature of the direct coupling between the C-terminal domain and the membrane, which is a key structural feature underlying K2P channel function.