An effective electron donor to cytochrome oxidase. Purification, identification, and kinetic characterization of a contaminant of ruthenium red, hexaamineruthenium II/III

When the calcium-transport inhibitor, ruthenium red, is chromatographed on a cation exchange resin, it yields a number of colored fractions and a colorless component that absorbs in the ultraviolet. The electron transfer activity previously ascribed to ruthenium red (Schwerzmann, K., Gazzotti, P., a...

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Bibliographic Details
Published in:The Journal of biological chemistry 1981-08, Vol.256 (16), p.8693-8698
Main Authors: Hochman, J.H., Partridge, B., Ferguson-Miller, S.
Format: Article
Language:English
Subjects:
Animals
Cattle
Electron Transport
Electron Transport Complex IV - metabolism
Kinetics
Mitochondria - enzymology
Mitochondria, Heart - enzymology
Ruthenium - isolation & purification
Ruthenium Compounds
Ruthenium Red - isolation & purification
Spectrophotometry, Infrared
Spectrophotometry, Ultraviolet
Submitochondrial Particles - enzymology
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Summary:When the calcium-transport inhibitor, ruthenium red, is chromatographed on a cation exchange resin, it yields a number of colored fractions and a colorless component that absorbs in the ultraviolet. The electron transfer activity previously ascribed to ruthenium red (Schwerzmann, K., Gazzotti, P., and Carafoli, E. (1976) Biochem. Biophys. Res. Commun. 69, 812) fractionates exclusively with the UV-absorbing material. On the basis of spectral, physical, and activity studies, we have identified this compound as Ru(NH3)62+/3+. It is shown that Ru(NH3)62+/3+ is an efficient electron donor directly to cytochrome oxidase, without mediation by cytochrome c. The steady state kinetics of electron transfer from Ru(NH3)62+ to purified oxidase resembles that of cytochrome c, showing a biphasic pattern but higher apparent Km values (Km1 = 8 microM, Km2 = 88 microM). Under conditions that favor tight binding to the oxidase, cytochrome c acts as a competitive inhibitor of Ru(NH3)62+, indicating that the two electron donors interact with cytochrome oxidase at the same site(s). The efficiency of Ru(NH3)62+ as an electron mediator to cytochrome aa3 and the similarity of its kinetic behavior to that of cytochrome c, make it a potentially valuable tool for investigating the mechanism of energy conservation in the terminal segment of the mitochondrial respiratory chain.
ISSN:0021-9258
1083-351X
DOI:10.1016/S0021-9258(19)68899-X