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The steady state behaviour of cytochrome c oxidase in proteoliposomes
Author(s) -
Nicholls Peter
Publication year - 1993
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(93)80168-t
Subject(s) - electron transfer , redox , chemistry , cytochrome , cytochrome c oxidase , electron transport chain , cytochrome c1 , ferrous , steady state (chemistry) , photochemistry , cytochrome b , hemeprotein , oxygen , ferric , cytochrome c , oxidation state , enzyme , crystallography , coenzyme q – cytochrome c reductase , heme , inorganic chemistry , biochemistry , mitochondrion , catalysis , organic chemistry , mitochondrial dna , gene
Electron transfer to oxygen catalysed by cytochrome c oxidase is accompanied by spectral changes at the binuclear a 3 Cu B centre, both in the soluble enzyme and in membranous systems, indicating spin or ligand state transitions of an iron that remains ferric. The other haem group, cytochrome a , does not change its spectral characteristics significantly during the steady state, but remains partially reduced until anaerobiosis. Cytochrome a 3 is fully oxidized in each of its major steady state forms, and reduced upon anaerobiosis to a single ferrous species. Although cytochrome a is normally the immediate electron donor to the binuclear centre, its redox state does not alter under conditions in which the flux through the enzyme is changing significantly. A second electron transfer pathway to the binuclear centre may therefore exist, possibly one in which direct reduction of the binuclear a 3 , Cu B centre by Cu A occurs. Both cytochrome a and Cu A behave as simple electron transfer centres. The energy‐conserving chemistry takes place at the binuclear centre in concert with the four‐electron reduction of molecular oxygen.