Structure of the transmembrane region of the M2 protein H+ channel

The transmembrane domain of the M2 protein from influenza A virus forms a n early uniform and ideal helix in a liquid crystalline bilayer environment. The exposure of the hydrophilic backbone structure is minimized through uni form hydrogen bond geometry imposed by the low dielectric lipid environment . A high-resolution structure of the monomer backbone and a detailed descri ption of its orientation with respect to the bilayer were achieved using or ientational restraints from solid-state NMR. With this unique information, the tetrameric structure of this H+ channel is constrained substantially. F eatures of numerous published models are discussed in light of the experime ntal structure of the monomer and derived features of the tetrameric bundle .