Time-resolved single-turnover of ba3 oxidase from Thermus thermophilus

The kinetics of the oxidation of fully-reduced ba3 cytochrome c oxidase from Thermus thermophilus by oxygen were followed by time-resolved optical spectroscopy and electrometry. Four catalytic intermediates were resolved during this reaction. The chemical nature and the spectral properties of three intermediates (compounds A, P and O) reproduce the general features of aa3-type oxidases. However the F intermediate in ba3 oxidase has a spectrum identical to the P state. This indicates that the proton taken up during the P → F transition does not reside in the binuclear site but is rather transferred to the covalently cross-linked tyrosine near that site. The total charge translocation associated with the F → O transition in ba3 oxidase is close to that observed during the F → O transition in the aa3 oxidases. However, the PR → F transition is characterized by significantly lower charge translocation, which probably reflects the overall lower measured pumping efficiency during multiple turnovers.