Figure 1. Comparison of the main proton channel network in as-isolated F306C mutant and wild-type AxNiR.

(a) The main proton channel of F306C has an additional water molecule, W2, that forms an hydrogen bond with the liganded water of the T2Cu ion. The 2F_o–F_c electron density map for F306C mutant contoured at the 1σ level. Distances from Cu atoms to coordinating protein atoms are shown as dotted red lines. Hydrogen bonds are shown in black dotted lines. Water molecules are shown as red spheres and Cu atoms as blue spheres. Residues are colour coded according to their chain. (b) Comparison between wild-type AxNiR (blue) and F306C mutant (green). Water molecules for the mutant are shown in red, whereas for wild-type protein in blue.