The protein effect in the structure of two ferryl-oxo intermediates at the same oxidation level in the heme copper binuclear center of cytochrome c oxidase.

Identification of the intermediates and determination of their structures in the reduction of dioxygen to water by cytochrome c oxidase (CcO) are particularly important to understanding both O2 activation and proton pumping by the enzyme. In this work, we report the products of the rapid reaction of O2 with the mixed valence form (CuA(2+), heme a(3+), heme a3(2+)-CuB(1+)) of the enzyme. The resonance Raman results show the formation of two ferryl-oxo species with characteristic Fe(IV)=O stretching modes at 790 and 804 cm(-1) at the peroxy oxidation level (PM).

The role of tryptophan 272 in the Paracoccus denitrificans cytochrome c oxidase.

The mechanism of electron coupled proton transfer in cytochrome c oxidase (CcO) is still poorly understood. The P(M)-intermediate of the catalytic cycle is an oxoferryl state whose generation requires one additional electron, which cannot be provided by the two metal centres. The missing electron has been suggested to be donated to this binuclear site by a tyrosine residue.

Tyrosine 167: the origin of the radical species observed in the reaction of cytochrome c oxidase with hydrogen peroxide in Paracoccus denitrificans.

Determination of the three-dimensional structure of cytochrome c oxidase, the terminal enzyme of the respiratory chain, from Paracoccus denitrificans offers the possibility of site-directed mutagenesis studies to investigate the relationship between the structure and the catalytic function of the enzyme. The mechanism of electron-coupled proton transfer is still, however, poorly understood. The P(M) intermediate of the catalytic cycle is an oxoferryl state the generation of which requires one additional electron, which cannot be provided by the two metal centers.