Electron Transfer in Monomeric Forms of Beef and Shark Heart Cytochrome c Oxidase

Academic Article


  • Beef heart cytochrome c oxidase is dimeric in reconstituted membranes and in nonionic detergents at physiological pH [Henderson, R., Capaldi, R. A., & Leigh, J. (1977) J. Mol. Biol. 112, 631; Robinson, N. C., & Capaldi, R. A. (1977) Biochemistry 16, 375], raising the possibility that this aggregation state is a prerequisite for enzymatic activity. A procedure for dissociating the enzyme into monomers is presented. This involves treating the protein with high concentrations of Triton X-100 at pH 8.5. The electron transfer activity of the monomer is comparable to that of the dimer under identical assay conditions. The beef heart cytochrome c oxidase monomer was found to be heterogeneous in hydro-dynamic studies, probably due to dissociation of associated polypeptides, including subunit III. Monomer molecular weights in the range 129000–160000 were obtained. Previous studies have indicated that shark heart cytochrome c oxidase is monomeric under physiological conditions. Sedimentation equilibrium studies reported here confirm this. The elasmobranch enzyme, with a similar polypeptide composition to that of the beef enzyme, was determined to have a molecular weight of 158 000. © 1983, American Chemical Society. All rights reserved.
  • Published In

  • Biochemistry  Journal
  • Digital Object Identifier (doi)

    Author List

  • Georgevich G; Darley-Usmar VM; Malatesta F; Capaldi RA
  • Start Page

  • 1317
  • End Page

  • 1322
  • Volume

  • 22
  • Issue

  • 6