Electron transfer between cytochrome. alpha. and copper A in cytochrome c oxidase: A perturbed equilibrium study

Journal Article · Tue Aug 22 00:00:00 EDT 1989 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00443a030· OSTI ID:5435782

Morgan, J E; Li, P M; Jang, D J; El-Sayed, M A; Chan, S I ^[1]

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1. California Institute of Technology, Pasadena (USA)

Intramolecular electron transfer in partially reduced cytochrome c oxidase has been studied by the perturbed equilibrium method. The authors have prepared a three-electron-reduced, CO-inhibited form of the enzyme in which cytochrome a and copper A are partially reduced and in an intramolecular redox equilibrium. When these samples were irradiated with a nitrogen laser to photodissociate the bound CO, changes in absorbance at 598 and 830 nm were observed which were consistent with a fast electron transfer from cytochrome a to copper A. The absorbance changes at 598 nm gave an apparent rate of 17,000 {plus minus} 2,000 s{sup {minus}1} (1 {sigma}), at pH 7.0 and 25.5{degree}C. These changes were not observed in either the CO mixed-valence or the CO-inhibited fully reduced forms of the enzyme. The rate was fastest at about pH 8.0, falling off toward both lower and higher pHs. There was a small but clear temperature dependence. The process was also observed in the cytochrome c-cytochrome c oxidase high-affinity complex. The electron equilibration measured between cytochrome {alpha} and copper A is far faster than any rate measured or inferred previously for this process.

• OSTI ID: 5435782
• Journal Information: Biochemistry; (USA), Vol. 28:17; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CARBON MONOXIDE
PHOTOLYSIS
CYTOCHROME OXIDASE
BIOCHEMICAL REACTION KINETICS
ELECTRON TRANSFER
STOICHIOMETRY
ABSORPTION SPECTROSCOPY
COPPER COMPOUNDS
CYTOCHROMES
GAS LASERS
IRON COMPOUNDS
LASER RADIATION
PH VALUE
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
DECOMPOSITION
ELECTROMAGNETIC RADIATION
ENZYMES
HAEM DEHYDROGENASES
KINETICS
LASERS
ORGANIC COMPOUNDS
OXIDES
OXIDOREDUCTASES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PIGMENTS
PROTEINS
RADIATIONS
REACTION KINETICS
SPECTROSCOPY
TRANSITION ELEMENT COMPOUNDS
550200* - Biochemistry