The c.d. spectra of Pseudomonas aeruginosa cytochrome c oxidase in the oxidized state and the reduced state are reported in the visible- and u.v. absorption regions. In the visible region the comparison between the spectra of reduced cytochrome c oxidase and ferrocytochrome c-551 allows the identification of the c.d. bands mainly due to the d1 haem chromophore in cytochrome c oxidase. In the near-u.v. region the assignment of some of the observed peaks to the haem groups and to the aromatic amino acid residues is proposed. A careful analysis of the data in the far-u.v. region leads to the determination of the relative amounts of alpha-helix and beta-sheet in the enzyme, giving for the first time a picture of its secondary structure. A significant difference in this respect between the reduced and the oxidized species is observed and discussed in the light of similar conclusions reported by other workers.
Circular-dichroic properties and secondary structure of Pseudomonas aeruginosa soluble cytochrome c oxidase
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M G Tordi, M C Silvestrini, A Colosimo, S Provencher, M Brunori; Circular-dichroic properties and secondary structure of Pseudomonas aeruginosa soluble cytochrome c oxidase. Biochem J 15 March 1984; 218 (3): 907–912. doi: https://doi.org/10.1042/bj2180907
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