Conformational plasticity of the influenza A M2 transmembrane helix in lipid bilayers under varying pH, drug binding, and membrane thickness

►Influenza M2 proton channel shows conformational plasticity due to the environment. ►Thicker lipid membranes and drug binding promote kinked M2TM helices. ►Channel opening promotes a more ideal helical conformation at histidine-37. ►Equilibrium between different conformations is shifted by the environment.