title: The multiplicity and stoichiometry of the prosthetic groups in QH2: cytochrome c oxidoreductase as studied by EPR.
abstract: 1. The EPR signal in the g = 2 region of the reduced QH2: cytochrome c oxidoreductase as present in submitochondrial particles and the isolated enzyme is an overlap of two signals in a 1 : 1 weighted ratio. Both signals are due to [2Fe-2S]+1 centers. 2. From the signal intensity it is computed that the concentration of each Fe-S center is half that of cytochrome c1. 3. The line shape of one of the Fe-S centers, defined as center 1, is reversibly dependent on the redox state of the b-c1 complex. The change of the line shape cannot be correlated with changes of the redox state of any of the cytochromes in QH2: cytochrome c oxidoreductase. 4. Lie the optical spectrum, the EPR spectrum of the cytochromes is composed of the absorption of at least three different b cytochromes and cytochrome c1. 5. The molar ratio of the prosthetic groups was found to be c1 : b-562 : b-566 : b-558 : center 1 : center 2 = 2 : 2 : 1 : 1 : 1 : 1. The consequences of this stoichiometry are discussed in relation to the basic enzymic unit of QH2 : cytochrome c oxidoreductase.
mesh_terms: D000818:Animals; D002417:Cattle; D003574:Cytochrome c Group; D004578:Electron Spin Resonance Spectroscopy; D005650:Fumarates / Q000378:metabolism; D066298:In Vitro Techniques; D007506:Iron-Sulfur Proteins; D008928:Mitochondria / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D010084:Oxidation-Reduction; D011808:Quinone Reductases / Q000378:metabolism*; D013367:Submitochondrial Particles / Q000378:metabolism*; D013386:Succinates / Q000378:metabolism; D013696:Temperature
chemical_list: D003574:Cytochrome c Group; D005650:Fumarates; D007506:Iron-Sulfur Proteins; D009097:Multienzyme Complexes; D013386:Succinates; D009247:NADH, NADPH Oxidoreductases; D011808:Quinone Reductases