Time-resolved single-turnover of ba3 oxidase from Thermus thermophilus (original) (raw)

The kinetics of the oxidation of fully-reduced ba 3 cytochrome c oxidase from Thermus thermophilus by oxygen were followed by timeresolved 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 aa 3 -type oxidases. However the F intermediate in ba 3 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 ba 3 oxidase is close to that observed during the F → O transition in the aa 3 oxidases. However, the P R → F transition is characterized by significantly lower charge translocation, which probably reflects the overall lower measured pumping efficiency during multiple turnovers.