title: Light-induced degradation of cytochrome b559 during photoinhibition of the photosystem II reaction center.
abstract: The behaviour of cytochrome (cyt) b559 during acceptor- and donor-side photoinhibition has been investigated in oxygen-evolving and non-evolving photosystem II (PSII) membranes. Strong illumination at 20 degrees C under aerobiosis induced a strong decrease in the absorbance of the cyt b559 alpha-band in the two preparations. This absorbance decline was observed only in non-oxygen-evolving PSII samples when illumination was performed under aerobiosis but at 4 degrees C, or under anaerobiosis at 20 degrees C. These results suggest that acceptor-side photoinhibition induces the degradation of cyt b559 by a mechanism related to an enzymatic reaction mediated by singlet oxygen. Donor-side photoinhibition may induce, however, a non-enzymatic photocleavage of the protein.
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla y CSIC, Spain. jmortega@cica.es
authors.forename: J M
authors.initials: JM
authors.lastname: Ortega
authors.forename: M
authors.initials: M
authors.lastname: Roncel
authors.forename: M
authors.initials: M
authors.lastname: Losada
mesh_terms: D003573:Cytochrome b Group / Q000737:chemistry / Q000378:metabolism*; D004579:Electron Transport; D004591:Electrophoresis, Polyacrylamide Gel; D007425:Intracellular Membranes / Q000201:enzymology / Q000378:metabolism; D008027:Light; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010782:Photolysis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism*; D045332:Photosystem II Protein Complex; D013053:Spectrophotometry; D018724:Spinacia oleracea / Q000201:enzymology
chemical_list: D003573:Cytochrome b Group; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; C019313:cytochrome b559; D010100:Oxygen