Specific Modification of Two Tryptophans within the Nuclear-Encoded Subunits of Bovine Cytochrome c Oxidase by Hydrogen Peroxide
Hydrogen peroxide does more than react with the binuclear center of oxidized bovine cytochrome c oxidase and generate the well-characterized “peroxy” and “ferryl” forms. Hydrogen peroxide also inactivates detergent-solubilized cytochrome c oxidase in a time- and concentration-dependent manner. There...
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Published in | Biochemistry (Easton) Vol. 43; no. 4; pp. 1003 - 1009 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
United States
American Chemical Society
03.02.2004
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Subjects | |
Online Access | Get full text |
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Summary: | Hydrogen peroxide does more than react with the binuclear center of oxidized bovine cytochrome c oxidase and generate the well-characterized “peroxy” and “ferryl” forms. Hydrogen peroxide also inactivates detergent-solubilized cytochrome c oxidase in a time- and concentration-dependent manner. There is a 70−80% decrease of electron-transport activity, peroxidation of bound cardiolipin, modification of two nuclear-encoded subunits (IV and VIIc), and dissociation of ∼60% of subunits VIa and VIIa. Modification of subunit VIIc and dissociation of subunit VIIa are coupled events that probably are responsible for the inactivation of cytochrome c oxidase. When cytochrome c oxidase is exposed to 500 μM hydrogen peroxide for 30 min at pH 7.4 and room temperature, subunits IV (modified up to 20%) and VIIc (modified up to 70%) each have an increased mass of 16 Da as detected by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and electrospray ionization mass spectrometry. In each case, the increased mass is caused by oxidation of a tryptophan (Trp19 within subunit VIIc and Trp48 within subunit IV), almost certainly due to formation of hydroxytryptophan. We conclude that hydrogen peroxide-induced oxidation of tryptophan and cardiolipin proceeds via the binuclear center since both modifications are prevented if the binuclear center is first blocked with cyanide. Bound cardiolipin and oxidized tryptophans are localized relatively far from the binuclear center (30−60 Å); therefore, oxidation probably occurs by migration of a free radical generated at the binuclear center to these distal reaction sites. |
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Bibliography: | istex:387479D32D4C6A7592656247824E2C1193F5063A ark:/67375/TPS-139RBR96-L This work was supported by grants from the National Institutes of Health (NIH GMS 24795), the Robert A. Welch Foundation (AQ1481), and the American Heart AssociationTexas Affiliate (0160115Y). Some aspects of this work were presented in preliminary form at the 12th European Bioenergetics Conference and 6th International Symposium on Mass Spectrometry in the Health and Life Sciences. ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0006-2960 1520-4995 |
DOI: | 10.1021/bi0358925 |