title: A cytochrome f/b6 complex of five polypeptides with plastoquinol-plastocyanin-oxidoreductase activity from spinach chloroplasts.
abstract: The isolation of a cytochrome f/b6 complex from spinach chloroplasts, with high yield and purity is reported. The complex consists of five polypeptides with a molecular mass of 34, 33, 23.5, 20 and 17.5 kDa, and contains one cytochrome f, two cytochromes b6 and the Rieske Fe-S center with two non-heme irons. It does not contain plastocyanin and is almost completely devoid of chlorophyll and carotenoids, but lipid and detergent are present. It is lacking cytochrome b-559, although three of the five polypeptides seem to carry heme groups. The preparation has plastoquinol-plastocyanin oxidoreductase activity with plastoquinol-1 and plastoquinol-9, which is sensitive to 2,5-dibromomethylisopropyl-p-benzoquinone, to 2-iodo-6-isopropyl-3-methyl-2',4',4'-trinitrodiphenyl ether, to 5-n-undecyl-6-hydroxy-4,7-dioxobenzothiazole, and to bathophenanthroline. Characteristics of this activity with respect to substrate concentrations, pH, detergent effect and other parameters are described.
mesh_terms: D002736:Chloroplasts / Q000378:metabolism*; D003580:Cytochromes / Q000302:isolation & purification / Q000378:metabolism*; D045348:Cytochromes f; D003902:Detergents / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D007700:Kinetics; D046911:Macromolecular Substances; D008970:Molecular Weight; D017830:Octoxynol; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000302:isolation & purification / Q000378:metabolism*; D010944:Plants / Q000378:metabolism; D011092:Polyethylene Glycols / Q000494:pharmacology
chemical_list: D003580:Cytochromes; D003902:Detergents; D046911:Macromolecular Substances; D011092:Polyethylene Glycols; D017830:Octoxynol; D045348:Cytochromes f; D010088:Oxidoreductases