Purification and Characterization of the Cytochrome c Oxidase from Rhodopseudomonas sphaeroides

Robert B. GENNIS, Robert P. CASEY, Angelo AZZI, Bernd LUDWIG

Research output: Contribution to journalArticlepeer-review

Abstract

When grown aerobically in the dark, Rhodopseudomonas sphaeroides develops a respiratory chain similar to that in mitochondria and the photosynthetic apparatus is suppressed. The aa3‐type cytochrome c oxidase from Rps. sphaeroides has been purified in Triton X‐100 by affinity chromatography with Sepharose 4B coupled to yeast cytochrome c. The oxidase contains 14 nmol heme a/mg protein and is composed of three polypeptide subunits with relative molecular masses of 45000, 37000 and 35000. The enzyme is highly active in the presence of detergents, with a maximal velocity of 300s−1/mol oxidase using either yeast or horse‐heart cytochrome c. The Rps. sphaeroides oxidase is cross‐reactive with antibodies directed against the oxidases from Paracoccus denitrificans and Saccharomyces cerevisiae. A particularly close relationship is indicated in the case of P. denitrificans. The Rps. sphaeroides oxidase has been incorporated into phospholipid vesicles. The resulting oxidase in these vesicles demonstrates high enzymatic activity and a respiratory control ratio of 5. Using these vesicles, no evidence for proton extrusion accompanying cytochrome c oxidation was observed. The data suggest that the Rps. sphaeroides oxidase does not function as a proton pump.

Original languageEnglish (US)
Pages (from-to)189-195
Number of pages7
JournalEuropean Journal of Biochemistry
Volume125
Issue number1
DOIs
StatePublished - Jun 1982

ASJC Scopus subject areas

  • Biochemistry

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