X-Ray Absorption Edge Studies on Oxidized and Reduced Cytochrome c Oxidase

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 74; no. 9; pp. 3821 - 3825
• Main Authors: Hu, Valerie W., Chan, Sunney I., Brown, George S.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 01.09.1977; National Acad Sciences
• Subjects: Absorption spectra; Animals; Atoms; Cattle; Chick Embryo; Copper; Cytochrome c Group; Cytochromes; Dogs; Electron Transport Complex IV; Energy levels; Iron; Ligands; Myocardium - enzymology; Oxidases; Oxidation; Oxidation-Reduction; Plastocyanin; Spectrum Analysis; Synchrotron radiation; X ray spectrum; X-Rays
• DOI: 10.1073/pnas.74.9.3821
• ISSN: 0027-8424

The x-ray absorption edge spectra of the Cu and Fe centers in oxidized and reduced cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase; EC 1.9.3.1) have been obtained using synchrotron radiation from the SPEAR storage ring at the Stanford Linear Accelerator Center. In addition, oxidized and reduced plastocyanin as well as a number of model copper compounds in various oxidation states were also examined. A comparison of the absorption edge fine structure of cytochrome oxidase with those of the models indicates that one of the two coppers in the oxidized protein is in the + 1 oxidation state. Upon reduction of the protein with dithionite, the second copper becomes Cu(I). The shift in the Fe K-edge of cytochrome oxidase upon reduction is small (about 2 eV or 3 × 10-19J) and is comparable to that previously observed for the reduction of the heme iron of cytochrome c.