This view of coevolving sites and proposed proton channels in the COI crystal structure shows the close co-localization of sites coevolving according to polarity and hydrophobicity (green spheres) with the H channel. The H, D and K channels are shown with red, cyan and yellow dots, respectively.

This view of coevolving sites and proposed proton channels in the COI crystal structure shows sites coevolving according to volume but not according to polarity or hydrophobicity (purple spheres). The H, D and K channels are shown with red, cyan and yellow dots, respectively.