Cytochrome c binding affects the conformation of cytochrome a in cytochrome c oxidase

J Biol Chem. 1992 Jan 5;267(1):298-302.

Abstract

Second derivative absorption spectroscopy has been used to assess the effects of complex formation between cytochrome c and cytochrome c oxidase on the conformation of the cytochrome a cofactor. When ferrocytochrome c is complexed to the cyanide-inhibited reduced or mixed valence enzyme, the conformation of ferrocytochrome a is affected. The second derivative spectrum of these enzyme forms displays two electronic transitions at 443 and 451 nm before complex formation, but only the 443-nm transition after cytochrome c is bound. This effect is not induced by poly-L-lysine, a homopolypeptide which is known to bind to the cytochrome c binding domain of cytochrome c oxidase. The effect is limited to cyanide-inhibited forms of the enzyme; no effect was observed for the fully reduced unliganded or fully reduced carbon monoxide-inhibited enzyme. The spectral signatures of these changes and the fact that they are exclusively associated with the cyanide-inhibited enzyme are both reminiscent of the effects of low pH on the conformation of cytochrome a (Ishibe, N., Lynch, S., and Copeland, R. A. (1991) J. Biol. Chem. 266, 23916-23920). These results are discussed in terms of possible mechanisms of communication between the cytochrome c binding site, cytochrome a, and the oxygen binding site within the cytochrome c oxidase molecule.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cattle
  • Cyanides / pharmacology
  • Cytochrome c Group / metabolism*
  • Electron Transport Complex IV / antagonists & inhibitors
  • Electron Transport Complex IV / chemistry
  • Electron Transport Complex IV / metabolism*
  • Oxidation-Reduction
  • Protein Conformation
  • Spectrum Analysis, Raman

Substances

  • Cyanides
  • Cytochrome c Group
  • Electron Transport Complex IV