title: Cytochrome b of fish mitochondria is strongly resistant to funiculosin, a powerful inhibitor of respiration.
abstract: We report here some unusual properties of ubiquinol: cytochrome c reductase of eel and other fish mitochondria. The turnover rate of the reductase is clearly higher than in mammalian mitochondria and the binding constant for ubiquinone seems to be larger than in other vertebrates. Additionally, the reductase activity of fish mitochondria is resistant to some powerful inhibitors that bind to cytochrome b, in particular to funiculosin. After sequencing most of the gene of eel cytochrome b and comparing the deduced amino acid sequence with that of other fish and animals, we hypothesize that the decreased binding of funiculosin could be due to a few amino acid replacements in the third and fourth transmembrane helix of the protein. In particular, the presence of methionine instead of alanine at position 125 seems to be largely responsible for the strong resistance to funiculosin and also to the partial resistance to myxothiazol in all fish mitochondria. Correlations between some residue substitutions in cytochrome b and the different effects of funiculosin in different species are also considered.
authors.affiliation: Department of Biology, University of Bologna, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Degli Esposti
authors.forename: A
authors.initials: A
authors.lastname: Ghelli
authors.forename: M
authors.initials: M
authors.lastname: Crimi
authors.forename: A
authors.initials: A
authors.lastname: Baracca
authors.forename: G
authors.initials: G
authors.lastname: Solaini
authors.forename: T
authors.initials: T
authors.lastname: Tron
authors.forename: A
authors.initials: A
authors.lastname: Meyer
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000880:Anthraquinones / Q000494:pharmacology; D000935:Antifungal Agents / Q000494:pharmacology; D001665:Binding Sites; D003573:Cytochrome b Group / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D004524:Eels / Q000378:metabolism; D014450:Electron Transport Complex III / Q000187:drug effects / Q000378:metabolism*; D005399:Fishes / Q000378:metabolism*; D008689:Methacrylates; D008928:Mitochondria / Q000201:enzymology; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012689:Sequence Homology, Nucleic Acid; D013844:Thiazoles / Q000494:pharmacology
chemical_list: D000880:Anthraquinones; D000935:Antifungal Agents; D003573:Cytochrome b Group; D008689:Methacrylates; D013844:Thiazoles; C015286:funiculosin (anthraquinone); C030517:myxothiazol; D014450:Electron Transport Complex III