Binuclear centre structure of terminal protonmotive oxidases.

The recent proliferation of data obtained from mutant forms of cytochrome oxidase and analogous enzymes has necessitated a re-examination of existing structural models. A new model is proposed, consistent with these data, which brings several protonatable residues (Y244, D298, D300, T309, T316, K319, T326) into the vicinity of the binuclear centre, suggestive of a proton-transferring function. In addition, we also consider those residues which may participate in electron transport between CuA and haem a. We suggest several potential lines of investigation.