Figure 7. Proposed proton channel in Gt cyt bd.
A series of conserved hydrophilic residues along with the propionate of heme d and internal water molecules that are not observed in the X-ray structure line a proton channel conveying protons from the cytoplasm to GtE378 (EcE445) and from there to the oxygenated species at the active site. (Figure made with VMD)