title: Redox changes of cytochrome b(559) in the presence of plastoquinones.
abstract: We have found that short chain plastoquinones effectively stimulated photoreduction of the low potential form of cytochrome b(559) and were also active in dark oxidation of this cytochrome under anaerobic conditions in Triton X-100-solubilized photosystem II (PSII) particles. It is also shown that molecular oxygen competes considerably with the prenylquinones in cytochrome b(559) oxidation under aerobic conditions, indicating that both molecular oxygen and plastoquinones could be electron acceptors from cytochrome b(559) in PSII preparations. alpha-Tocopherol quinone was not active in the stimulation of cytochrome photoreduction but efficiently oxidized it in the dark. Both the observed photoreduction and dark oxidation of the cytochrome were not sensitive to 3-(3,4-dichlorophenyl)-1, 1-dimethylurea. It was concluded that both quinone-binding sites responsible for the redox changes of cytochrome b(559) are different from either the Q(A) or Q(B) site in PSII and represent new quinone-binding sites in PSII.
authors.affiliation: Department of Plant Physiology and Biochemistry, The Jan Zurzycki Institute of Molecular Biology, Jagiellonian University, Aleja Mickiewicza 3, 31-120 Kraków, Poland.
authors.forename: J
authors.initials: J
authors.lastname: Kruk
authors.forename: K
authors.initials: K
authors.lastname: Strzalka
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D003573:Cytochrome b Group / Q000737:chemistry / Q000378:metabolism*; D003624:Darkness; D004579:Electron Transport / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000378:metabolism; D007700:Kinetics; D008027:Light; D008954:Models, Biological; D017830:Octoxynol / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D010100:Oxygen / Q000378:metabolism; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism*; D045332:Photosystem II Protein Complex; D010971:Plastoquinone / Q000378:metabolism* / Q000494:pharmacology; D012995:Solubility; D013053:Spectrophotometry; D014810:Vitamin E / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D014812:Vitamin K / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D003573:Cytochrome b Group; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D014812:Vitamin K; D014810:Vitamin E; C002421:tocopherylquinone; D017830:Octoxynol; C019313:cytochrome b559; D006861:Hydrogen Peroxide; D010971:Plastoquinone; D010100:Oxygen; C023885:menadiol