Time-resolved optical absorption studies of cytochrome oxidase dynamics

Biochim Biophys Acta. 2004 Apr 12;1655(1-3):263-73. doi: 10.1016/j.bbabio.2003.07.011.

Abstract

Time-resolved spectroscopic studies in our laboratory of bovine heart cytochrome c oxidase dynamics are summarized. Intramolecular electron transfer was investigated upon photolysis of CO from the mixed-valence enzyme, by pulse radiolysis, and upon light-induced electron injection into the cytochrome c/cytochrome oxidase complex from a novel photoactivatable dye. The reduction of dioxygen to water was monitored by a gated multichannel analyzer using the CO flow-flash method or a synthetic caged dioxygen carrier. The pH dependence of the intermediate spectra suggests a mechanism of dioxygen reduction more complex than the conventional unidirectional sequential scheme. A branched model is proposed, in which one branch produces the P form and the other branch the F form. The rate of exchange between the two branches is pH-dependent. A cross-linked histidine-phenol was synthesized and characterized to explore the role of the cross-linked His-Tyr cofactor in the function of the enzyme. Time-resolved optical absorption spectra, EPR and FTIR spectra of the compound generated after UV photolysis indicated the presence of a radical residing primarily on the phenoxyl ring. The relevance of these results to cytochrome oxidase function is discussed.

Publication types

  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Animals
  • Cattle
  • Electron Spin Resonance Spectroscopy
  • Electron Transport
  • Electron Transport Complex IV / chemistry*
  • Electron Transport Complex IV / metabolism*
  • Hydrogen-Ion Concentration
  • In Vitro Techniques
  • Models, Chemical
  • Myocardium / enzymology
  • Oxidation-Reduction
  • Oxygen / metabolism
  • Photolysis
  • Proton-Motive Force
  • Spectrophotometry
  • Spectroscopy, Fourier Transform Infrared
  • Tyrosine / chemistry
  • Water / metabolism

Substances

  • Water
  • Tyrosine
  • Electron Transport Complex IV
  • Oxygen