title: Structural and functional characteristics of polypeptide subunits of the bovine heart ubiquinol--cytochrome-c reductase complex.
abstract: Structural and functional characteristics of subunits of bovine heart cytochrome-c reductase have been investigated by controlled digestion of soluble and membrane-reconstituted purified bc1 complex and direct amino acid sequencing of native and digested protein subunits. The results obtained show that the N-terminal segments of core protein II and the 14-kDa protein extend at the periphery of the complex, protruding into the inner matrix space. The Fe-S protein, located at the outer C-periphery of the complex, is shown to be anchored to other subunits of the complex by the amphipathic N-terminal region. Proteolytic cleavage of 7-11 residues from the N-terminal segment of the 14-kDa protein is apparently associated with decoupling of redox-linked proton pumping. Partial digestion of core protein II, the 6.4-kDa protein, and the C-terminal region of the 9.2-kDa protein, is without effect on the redox and proton-motive activity of the complex.
authors.affiliation: Institute of Medical Biochemistry and Chemistry, University of Bari, Italy.
authors.forename: T
authors.initials: T
authors.lastname: Cocco
authors.forename: M
authors.initials: M
authors.lastname: Lorusso
authors.forename: A M
authors.initials: AM
authors.lastname: Sardanelli
authors.forename: M
authors.initials: M
authors.lastname: Minuto
authors.forename: S
authors.initials: S
authors.lastname: Ronchi
authors.forename: G
authors.initials: G
authors.lastname: Tedeschi
authors.forename: S
authors.initials: S
authors.lastname: Papa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D014450:Electron Transport Complex III / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D008929:Mitochondria, Heart / Q000201:enzymology*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000302:isolation & purification; D014357:Trypsin
chemical_list: D010446:Peptide Fragments; D014357:Trypsin; D014450:Electron Transport Complex III