Binding and oxidation of mutant cytochromes c by cytochrome-c oxidase.
Mutation of conserved Phe-82 of yeast iso-1 cytochrome c to Tyr, Gly, Ser, Leu, or Ile affects binding to and reaction with cytochrome-c oxidase from beef heart. The observed changes of binding and kinetic constants reflect mutation-induced rearrangements in the heme vicinity brought about by the replacement of Phe-82. Such conformational rearrangements are also revealed by altered circular dichroism spectra of the oxidase-bound mutant cytochromes c. Variations in Km for cytochrome c oxidation do not parallel variations in Kd, the dissociation constant for binding of cytochrome c to the oxidase. This observation does not support an enzymatic mechanism in which the rate of cytochrome c oxidation is governed by product dissociation.
Michel
B
B
Department of Biochemistry, University of Zürich, Switzerland.
Mauk
A G
AG
Bosshard
H R
HR
D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D003574:Cytochrome c Group / Q000235:genetics / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000378:metabolism*; D007700:Kinetics; D009206:Myocardium / Q000201:enzymology; D010084:Oxidation-Reduction; D011485:Protein Binding; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000201:enzymology
D003574:Cytochrome c Group; D003576:Electron Transport Complex IV