Deuterium isotope effect of proton pumping in cytochrome c oxidase
| Autor: | Gisela Brändén, Peter Brzezinski, Lina Salomonsson |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
Respiratory chain
Biophysics Photochemistry Crystallography X-Ray Biochemistry Proton transfer Electron transfer Electron Transport Electron Transport Complex IV Cytochrome C1 Cytochrome c oxidase Transmembrane transport Spectroscopy biology Chemistry Cytochrome c Cytochrome aa3 Cell Biology Hydrogen-Ion Concentration Proton Pumps Deuterium Electron transport chain Proton pump Mitochondria Kinetics Membrane protein biology.protein |
| Zdroj: | Biochimica et biophysica acta. 1777(4) |
| ISSN: | 0006-3002 |
| Popis: | In mitochondria and many aerobic bacteria cytochrome c oxidase is the terminal enzyme of the respiratory chain where it catalyses the reduction of oxygen to water. The free energy released in this process is used to translocate (pump) protons across the membrane such that each electron transfer to the catalytic site is accompanied by proton pumping. To investigate the mechanism of electron–proton coupling in cytochrome c oxidase we have studied the pH-dependence of the kinetic deuterium isotope effect of specific reaction steps associated with proton transfer in wild-type and structural variants of cytochrome c oxidases in which amino-acid residues in proton-transfer pathways have been modified. In addition, we have solved the structure of one of these mutant enzymes, where a key component of the proton-transfer machinery, Glu286, was modified to an Asp. The results indicate that the P3→F3 transition rate is determined by a direct proton-transfer event to the catalytic site. In contrast, the rate of the F3→O4 transition, which involves simultaneous electron transfer to the catalytic site and is characteristic of any transition during CytcO turnover, is determined by two events with similar rates and different kinetic isotope effects. These reaction steps involve transfer of protons, that are pumped, via a segment of the protein including Glu286 and Arg481. |
| Databáze: | OpenAIRE |
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