title: Superoxides from mitochondrial complex III: the role of manganese superoxide dismutase.
abstract: In this report we show that ubiquinone cytochrome c reductase (complex III) from isolated rat heart mitochondria when inhibited with antimycin A, produces a large amount of superoxide as measured by the chemiluminescent probe coelenterazine. When mitochondria are inhibited with myxothiazol or stigmatellin, there is no detectable formation of superoxide. The antimycin A-sensitive free radical production can be dramatically reduced using either myxothiazol or stigmatellin. This suggests that the antimycin A-sensitive generation of superoxides originates primarily from the Q(o) semiubiquinone. When manganese superoxide dismutase depleted submitochondrial particles (SMP) were inhibited with myxothiazol or stigmatellin, a large superoxide signal was observed. These two inhibitors likely increase the concentration of the Q(i) semiquinone at the N center. The antimycin A-sensitive signal can, in the case of both the mitochondria and the SMP, be dissipated by the addition of copper zinc superoxide dismutase, suggesting that the measured coelenterazine signal was a result of superoxide production. Taken together, this data suggests that free radicals generated from the Q(i) species are more effectively eliminated by MnSOD in intact mitochondria.
authors.affiliation: Hospital for Sick Children, Metabolism Research Programme, Toronto, ON, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Raha
authors.forename: G E
authors.initials: GE
authors.lastname: McEachern
authors.forename: A T
authors.initials: AT
authors.lastname: Myint
authors.forename: B H
authors.initials: BH
authors.lastname: Robinson
mesh_terms: D000818:Animals; D000968:Antimycin A / Q000494:pharmacology; D014450:Electron Transport Complex III / Q000378:metabolism*; D005609:Free Radicals / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D008689:Methacrylates; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism*; D008956:Models, Chemical; D011090:Polyenes / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013367:Submitochondrial Particles / Q000187:drug effects / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism*; D013844:Thiazoles / Q000494:pharmacology
chemical_list: D005609:Free Radicals; D007527:Isoenzymes; D008689:Methacrylates; D011090:Polyenes; D013844:Thiazoles; D013481:Superoxides; D000968:Antimycin A; C030517:myxothiazol; C041573:stigmatellin; D013482:Superoxide Dismutase; D014450:Electron Transport Complex III