title: Protein-ubiquinone interaction in bovine heart mitochondrial succinate-cytochrome c reductase. Synthesis and biological properties of fluorine substituted ubiquinone derivatives.
abstract: To investigate the protein-ubiquinone interaction in the bovine heart mitochondrial succinate-cytochrome c reductase region of the respiratory chain, three fluorine substituted ubiquinone derivatives, 2,3-dimethoxy-6-(9'-fluorodecyl)-1,4-benzoquinone (9FQ), 2-methoxy-5-trifluoromethyl-6-decyl-1,4-benzoquinone (TFQ), and 2-methoxy-5-trifluoromethyl-6-(9'-fluorodecyl)-1,4-benzoquinone (9FTFQ), were synthesized. 9FQ was synthesized by radical coupling of Q0 and bis(10-fluoroundecanoyl)peroxide. The latter was prepared by fluorination of undecylenic acid followed by thionylchloride treatment and peroxidation. TFQ was synthesized from 2,2,2-trifluoro-p-cresol by methylation, nitration, reduction, acetylation, nitration, reduction, oxidation, and radical alkylation. 9FTFQ was prepared by the radical alkylation of 2-methoxy-5-trifluoromethyl-1,4-benzoquinone with bis(10-fluoroundecanoyl)peroxide. All three fluoro-Q derivatives are active (greater than 50% the activity of 2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone) when used as electron acceptors for succinate-ubiquinone reductase. However, only 9FQ is active when used as an electron donor for ubiquinol-cytochrome c reductase or as an electron mediator for succinate-cytochrome c reductase. Both TFQ and 9FTFQ are competitive inhibitors for ubiquinol-cytochrome c reductase. A 19FNMR peak-broadening effect was observed for 9FQ when it was reconstituted with ubiquinone-depleted ubiquinol-cytochrome c reductase. A drastic up-field chemical shift was observed for TFQ when it was reconstituted with ubiquinone-depleted reductase. These results indicate that the binding environments of the benzoquinone ring and the alkyl side chain of the Q molecule are different. The strong up-field chemical shift for TFQ, and lack of significant chemical shift for 9FQ, suggest that the benzoquinone ring is bound near the paramagnetic cytochrome b heme.
authors.affiliation: Department of Biochemistry, Oklahoma State University, Stillwater 74078.
authors.forename: F
authors.initials: F
authors.lastname: Yang
authors.forename: L
authors.initials: L
authors.lastname: Yu
authors.forename: D Y
authors.initials: DY
authors.lastname: He
authors.forename: C A
authors.initials: CA
authors.lastname: Yu
mesh_terms: D000818:Animals; D002417:Cattle; D004579:Electron Transport; D042963:Electron Transport Complex II; D014450:Electron Transport Complex III / Q000378:metabolism*; D005461:Fluorine; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D008929:Mitochondria, Heart / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism*; D012995:Solubility; D013329:Structure-Activity Relationship; D013385:Succinate Dehydrogenase / Q000378:metabolism*; D014451:Ubiquinone / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism*
chemical_list: D009097:Multienzyme Complexes; D014451:Ubiquinone; D005461:Fluorine; D010088:Oxidoreductases; D042963:Electron Transport Complex II; D013385:Succinate Dehydrogenase; D014450:Electron Transport Complex III; C003741:ubiquinol