Tryptophan 334 oxidation in bovine cytochrome c oxidase subunit I involves free radical migration |
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Authors: | Lemma-Gray Patrizia Weintraub Susan T Carroll Christopher A Musatov Andrej Robinson Neal C |
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Affiliation: | Department of Biochemistry, The University of Texas Health Science Center, MC 7760, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA. |
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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. |
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Keywords: | CcO, cytochrome c oxidase HPLC, high-performance liquid chromatography HPLC-ESI/MS/MS, reversed-phase HPLC with electrospray ionization tandem mass spectrometry detection and analysis MALDI-TOF/MS, matrix-assisted laser desorption ionization time-of-flight mass spectrometry ROS, reactive oxygen species |
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