The operation of the alternative electron-leak pathways mediated by cytochrome c in mitochondria.
Low (1 x 10(-9)M) concentrations of cytochrome c inhibit H2O2 production in cytochrome c-depleted mitochondria, purified succinate-cytochrome c reductase (SCR) and antimycin A inhibited cytochrome c-depleted HMP. At higher concentration (2 x 10(-6)M), cytochrome c eliminates pre-existed H2O2 if feeding electrons to it by succinate. Cytochrome c also decreases the OH* produced by succinate-cytochrome c reductase oxidizing succinate. We conclude that the alternative electron-leak pathway mediated by cytochrome c operates very well. In the presence of antimycin A, ferrocytochrome c can suppress the generation of H2O2 in SCR system, but ferricytochrome c cannot. Similar results are obtained on the elimination of pre-existed H2O2 by cytochrome c. For hydroxyl radical, antimycin A abolishes the suppression caused by both ferrocytochrome c and ferricytochrome c. These results indicate that the reductive state of cytochrome c caused by electron-flow is necessary and sufficient for the operation of cytochrome c-mediated electron-leakage pathway.
Zhao
Yungang
Y
Institute of Biophysics, Chinese Academy of Science, Beijing 100101, China.
Xu
Jian-Xing
JX
D000818:Animals; D000968:Antimycin A / Q000494:pharmacology; D045304:Cytochromes c / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004579:Electron Transport; D006861:Hydrogen Peroxide / Q000378:metabolism; D017665:Hydroxyl Radical / Q000378:metabolism; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism*; D013053:Spectrophotometry; D013384:Succinate Cytochrome c Oxidoreductase / Q000378:metabolism; D013552:Swine
D017665:Hydroxyl Radical; D000968:Antimycin A; D045304:Cytochromes c; D006861:Hydrogen Peroxide; D013384:Succinate Cytochrome c Oxidoreductase