Fig. 1.

Structure and mechanistic model of the M2 proton channel. A Pore structure in the closed state (Sharma et al. 2010). Three key residues, Val27, His37, and Trp41, are indicated. Light shading indicates the lipid bilayer. B The model for calculating the rate of ion transport. Note that k_e+ and k_i+ are effective rate constants, involving the whole process of a proton starting in the exterior or interior bulk solution, diffusing into the dynamic channel and to the internal site, and finally binding to it. The green boxes indicate the Val27 and Trp41 gates. C Details of the Val27 and Trp41 gates.