Redox-linked conformational changes in cytochromecoxidase

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Abstract
The CD spectrum of oxidized cytochrome oxidase in the wavelength region 185–260 nm shows that the secondary structure of the protein consists of close to 60% α-helix and slightly less than 20% β-structure. CD spectra of oxidized cytochrome oxidase, of half and fully reduced carboxycytochrome oxidase as well as of fully reduced cytochrome oxidase, have been recorded in the wavelength region 200–260 nm. The results demonstrate a conformational change on going from the oxidized to the half reduced state in carboxycytochrome oxidase; no further change occurs on full reduction. A conformational change is also seen in the fully reduced enzyme without bound CO. The conformational transitions are suggested to be part of the proton pumping mechanism of cytochrome oxidase.