Cytochrome Oxidase: An Alternative Model

Oxidative titration of reduced cytochrome oxidase (cytochrome c oxidase; ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1) in the presence of carbon monoxide and sulfide, at potentials greater than +500 mV (vs. the neutral hydrogen electrode), have failed to produce new copper signals in the elec...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1980-04, Vol.77 (4), p.1806-1808
Main Authors: Seiter, C. H. A., Angelos, S. G.
Format: Article
Language:English
Subjects:
Animals
Biochemistry
Carbon Monoxide
Cattle
Copper
Cytochromes
Electron Spin Resonance Spectroscopy
Electron Transport Complex IV
Enzymes
Ligands
Mitochondria, Heart - enzymology
Oxidases
Oxidation
Oxidation-Reduction
Oxides
Porphyrins
Protein Conformation
Spectrum Analysis, Raman
Sulfides
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Summary:Oxidative titration of reduced cytochrome oxidase (cytochrome c oxidase; ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1) in the presence of carbon monoxide and sulfide, at potentials greater than +500 mV (vs. the neutral hydrogen electrode), have failed to produce new copper signals in the electron paramagnetic resonance spectrum of this enzyme. This observation implies that one of the copper centers in cytochrome oxidase remains Cu(I) under strongly oxidizing conditions. The rationalization of this fact, and the possible explanation of a great accumulation of spectroscopic data, is that cytochrome a3may be a two-electron redox center, with stable Fe(IV), Fe(III), and Fe(II) states during its redox cycle. This oxidase model does not require an antiferromagnetic coupling scheme, in contrast to currently prevalent models.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.77.4.1806