| 18555026 |
Thariat J, Collin F, Marchetti C, Ahmed-Adrar NS, Vitrac H, Jore D, Gardes-Albert M: Marked difference in cytochrome c oxidation mediated by HO (*) and/or O (2)(*-) free radicals in vitro. Biochimie. 2008 Oct;90(10):1442-51. Epub 2008 May 27.
Cytochrome c (cyt c) is an electron carrier involved in the mitochondrial respiratory chain and a critical protein in apoptosis. The oxidation of cytochrome c can therefore be relevant biologically. We studied whether cytochrome c underwent the attack of reactive oxygen species (ROS) during ionizing irradiation-induced oxidative stress. ROS were generated via water radiolysis under ionizing radiation (IR) in vitro. Characterization of oxidation was performed by mass spectrometry, after tryptic digestion, and UV-visible spectrophotometry. When both hydroxyl and superoxide free radicals were generated during water radiolysis, only five tryptic peptides of cyt c were reproducibly identified as oxidized according to a relation that was dependent of the dose of ionizing radiation. The same behavior was observed when hydroxyl free radicals were specifically generated (N (2) O-saturated solutions). Specific oxidation of cyt c by superoxide free radicals was performed and has shown that only one oxidized peptide (MIFAGIK+16), corresponding to the oxidation of Met80 into methionine sulfoxide, exhibited a radiation dose-dependent formation. In addition, the enzymatic site of cytochrome c was sensitive to the attack of both superoxide and hydroxyl radicals as observed through the reduction of Fe (3+), the degradation of the protoporphyrin IX and the oxidative disruption of the Met80-Fe (3+) bond. Noteworthy, the latter has been involved in the conversion of cyt c to a peroxidase. Finally, Met80 appears as the most sensitive residue towards hydroxyl but also superoxide free radicals mediated oxidation. |
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