Temperature dependence of the reduction potential in CuA in carbon monoxide-inhibited cytochrome c oxidase

• Published in: Biochemistry (Easton) Vol. 25; no. 1; pp. 167 - 171
• Main Authors: Wang, Hsin, Blair, David F, Ellis, Walther R, Gray, Harry B, Chan, Sunney I
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 14.01.1986
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Applied sciences; Binding Sites; Biological and medical sciences; Carbon Monoxide - pharmacology; Cattle; Copper - metabolism; Electron Transport Complex IV - antagonists & inhibitors; Enzymes and enzyme inhibitors; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Kinetics; Metalloproteins - metabolism; Mitochondria, Heart - enzymology; Other techniques and industries; Oxidation-Reduction; Oxidoreductases; Protein Binding; Spectrophotometry, Infrared - methods; Thermodynamics; Heart; Cytochrome c oxidase; Temperature; Enzyme; Ox; Absorption spectrometry; Vertebrata; Respiratory chain; Mammalia; Electrochemistry; Artiodactyla; Carbon monoxide; Inhibition; Redox potential; Copper; Ungulata
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00349a024

The temperature dependence of the reduction potential of the CuA site in carbon monoxide inhibited cytochrome c oxidase has been measured with a spectroelectrochemical method adapted to the relatively weak near-infrared absorption of this copper ion. These measurements, together with parallel measurements on the 604-nm absorption due to Fea, indicate that an interaction between CuA and Fea causes the reduction potential for one of these sites to be decreased by approximately 40 mV upon reduction of the other. The temperature dependence of the CuA reduction potential indicates a relatively large and negative standard entropy of reduction of CuA (delta So' = -48.7 +/- 2.3 eu). Possible implications of the intersite redox interaction and the large standard entropy of reduction of the CuA site are discussed.