title: Tryptophan 334 oxidation in bovine cytochrome c oxidase subunit I involves free radical migration.
abstract: A single tryptophan (W(334(I))) within the mitochondrial-encoded core subunits of cytochrome c oxidase (CcO) is selectively oxidized when hydrogen peroxide reacts with the binuclear center. W(334(I)) is converted to hydroxytryptophan as identified by reversed-phase HPLC-electrospray ionization tandem mass spectrometry analysis of peptides derived from the three SDS-PAGE purified subunits. Total sequence coverage of subunits I, II and III was limited to 84%, 66% and 54%, respectively. W(334(I)) is located on the surface of CcO at the membrane interface. Two other surface tryptophans within nuclear-encoded subunits, W(48(IV)) and W(19(VIIc)), are also oxidized when hydrogen peroxide reacts with the binuclear center (Musatov et al. (2004) Biochemistry 43, 1003-1009). Two aromatic-rich networks of amino acids were identified that link the binuclear center to the three oxidized tryptophans. We propose the following mechanism to explain these results. Electron transfer through the aromatic networks moves the free radicals generated at the binuclear center to the surface-exposed tryptophans, where they produce hydroxytryptophan.
authors.affiliation: Department of Biochemistry, The University of Texas Health Science Center, MC 7760, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Lemma-Gray
authors.forename: Susan T
authors.initials: ST
authors.lastname: Weintraub
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Carroll
authors.forename: Andrej
authors.initials: A
authors.lastname: Musatov
authors.forename: Neal C
authors.initials: NC
authors.lastname: Robinson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005609:Free Radicals / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000378:metabolism; D066298:In Vitro Techniques; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits; D021241:Spectrometry, Mass, Electrospray Ionization; D014364:Tryptophan / Q000737:chemistry
chemical_list: D005609:Free Radicals; D010446:Peptide Fragments; D021122:Protein Subunits; D014364:Tryptophan; D006861:Hydrogen Peroxide; D003576:Electron Transport Complex IV