title: Absence of the psbH gene product destabilizes photosystem II complex and bicarbonate binding on its acceptor side in Synechocystis PCC 6803.
abstract: The PsbH protein, a small subunit of the photosystem II complex (PSII), was identified as a 6-kDa protein band in the PSII core and subcore (CP47-D1-D2-cyt b-559) from the wild-type strain of the cyanobacterium Synechocystis PCC 6803. The protein was missing in the D1-D2-cytochrome b-559 complex and also in all PSII complexes isolated from IC7, a mutant lacking the psbH gene. The following properties of PSII in the mutant contrasted with those in wild-type: (a) CP47 was released during nondenaturing electrophoresis of the PSII core isolated from IC7; (b) depletion of CO2 resulted in a reversible decrease of the QA- reoxidation rate in the IC7 cells; (c) light-induced decrease in PSII activity, measured as 2,5-dimethyl-benzoquinone-supported Hill reaction, was strongly dependent on the HCO3- concentration in the IC7 cells; and (d) illumination of the IC7 cells lead to an extensive oxidation, fragmentation and cross-linking of the D1 protein. We did not find any evidence for phosphorylation of the PsbH protein in the wild-type strain. The results showed that in the PSII complex of Synechocystis attachment of CP47 to the D1-D2 heterodimer appears weakened and binding of bicarbonate on the PSII acceptor side is destabilized in the absence of the PsbH protein.
authors.affiliation: Photosynthesis Research Centre, University of South Bohemia, Ceské Budejovice, Czech Republic. komenda@alga.cz
authors.forename: Josef
authors.initials: J
authors.lastname: Komenda
authors.forename: Lenka
authors.initials: L
authors.lastname: Lupínková
authors.forename: Jirí
authors.initials: J
authors.lastname: Kopecký
mesh_terms: D001639:Bicarbonates / Q000378:metabolism*; D000458:Cyanobacteria / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress; D010750:Phosphoproteins / Q000235:genetics*; D010766:Phosphorylation; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics* / Q000378:metabolism*; D045332:Photosystem II Protein Complex; D011485:Protein Binding; D014357:Trypsin / Q000378:metabolism
chemical_list: D001639:Bicarbonates; D010750:Phosphoproteins; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; C063224:photosystem II, psbH subunit; D014357:Trypsin