Definition of the catalytic site of cytochrome c oxidase: specific ligands of heme a and the heme a3-CuB center
| Autor: | Younkyoo Kim, James P. Shapleigh, Jonathan P. Hosler, Robert B. Gennis, Mary M. J. Tecklenburg, Gerald T. Babcock, Shelagh Ferguson-Miller |
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| Rok vydání: | 1992 |
| Předmět: |
Hemeprotein
Protein Conformation Molecular Sequence Data Heme Rhodobacter sphaeroides Spectrum Analysis Raman Electron Transport Complex IV chemistry.chemical_compound Cytochrome c oxidase Histidine Amino Acid Sequence Oxidase test Binding Sites Multidisciplinary biology Cytochrome b Spectrum Analysis Membrane Proteins Heme A chemistry Biochemistry Mutagenesis Site-Directed biology.protein Cytochrome aa3 Copper Research Article |
| Zdroj: | Proceedings of the National Academy of Sciences. 89:4786-4790 |
| ISSN: | 1091-6490 0027-8424 |
| DOI: | 10.1073/pnas.89.11.4786 |
| Popis: | The three-subunit aa3-type cytochrome c oxidase (EC 1.9.3.1) of Rhodobacter sphaeroides is structurally and functionally homologous to the more complex mitochondrial oxidase. The largest subunit, subunit I, is highly conserved and predicted to contain 12 transmembrane segments that provide all the ligands for three of the four metal centers: heme a, heme a3, and CuB. A variety of spectroscopic techniques identify these ligands as histidines. We have used site-directed mutagenesis to change all the conserved histidines within subunit I of cytochrome c oxidase from Rb. sphaeroides. Analysis of the membrane-bound and purified mutant proteins by optical absorption and resonance Raman spectroscopy indicates that His-102 and His-421 are the ligands of heme a, while His-284, His-333, His-334, and His-419 ligate the heme a3-CuB center. To satisfy this ligation assignment, helices II, VI, VII, and X, which contain these histidine residues, must be in close proximity. These data provide empirical evidence regarding the three-dimensional protein structure at the catalytic core of cytochrome c oxidase. |
| Databáze: | OpenAIRE |
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