Mechanisms of proton conduction and gating in influenza M2 proton channels from solid-state NMR.
The M2 protein of influenza viruses forms an acid-activated tetrameric proton channel. We used solid-state nuclear magnetic resonance spectroscopy to determine the structure and functional dynamics of the pH-sensing and proton-selective histidine-37 in M2 bound to a cholesterol-containing virus-envelope-mimetic membrane so as to better understand the proton conduction mechanism. In the high-pH closed state, the four histidines form an edge-face π-stacked structure, preventing the formation of a hydrogen-bonded water chain to conduct protons. In the low-pH conducting state, the imidazoliums hydrogen-bond extensively with water and undergo microsecond ring reorientations with an energy barrier greater than 59 kilojoules per mole. This barrier is consistent with the temperature dependence of proton conductivity, suggesting that histidine-37 dynamically shuttles protons into the virion. We propose a proton conduction mechanism in which ring-flip-assisted imidazole deprotonation is the rate-limiting step.
Department of Chemistry, Iowa State University, Ames, IA 50011, USA.
Fanghao
F
Hu
Wenbin
W
Luo
Mei
M
Hong
D006639:Histidine / Q000737:chemistry / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000737:chemistry / Q000378:metabolism; D009980:Influenza A virus / Q000502:physiology*; D015640:Ion Channel Gating / Q000502:physiology*; D007473:Ion Channels / Q000737:chemistry / Q000502:physiology*; D019906:Nuclear Magnetic Resonance, Biomolecular; D011522:Protons; D014763:Viral Matrix Proteins / Q000737:chemistry / Q000502:physiology*; D014867:Water / Q000737:chemistry; D000086082:Viroporin Proteins
D006639:Histidine; D007093:Imidazoles; D007473:Ion Channels; D011522:Protons; D014763:Viral Matrix Proteins; D014867:Water; C488937:M2 protein, Influenza A virus; D000086082:Viroporin Proteins; C029899:imidazole