title: Amino acid oxidation of the D1 and D2 proteins by oxygen radicals during photoinhibition of Photosystem II.
abstract: The Photosystem II reaction center is vulnerable to photoinhibition. The D1 and D2 proteins, lying at the core of the photosystem, are susceptible to oxidative modification by reactive oxygen species that are formed by the photosystem during illumination. Using spin probes and EPR spectroscopy, we have determined that both O2•-and HO•are involved in the photoinhibitory process. Using tandem mass spectroscopy, we have identified a number of oxidatively modified D1 and D2 residues. Our analysis indicates that these oxidative modifications are associated with formation of HO•at both the Mn4O5Ca cluster and the nonheme iron. Additionally, O2•-appears to be formed by the reduction of O2at either PheoD1or QAEarly oxidation of D1:332H, which is coordinated with the Mn1 of the Mn4O5Ca cluster, appears to initiate a cascade of oxidative events that lead to the oxidative modification of numerous residues in the C termini of the D1 and D2 proteins on the donor side of the photosystem. Oxidation of D2:244Y, which is a bicarbonate ligand for the nonheme iron, induces the propagation of oxidative reactions in residues of the D-deloop of the D2 protein on the electron acceptor side of the photosystem. Finally, D1:130E and D2:246M are oxidatively modified by O2•-formed by the reduction of O2either by PheoD1•-or QA•-The identification of specific amino acid residues oxidized by reactive oxygen species provides insights into the mechanism of damage to the D1 and D2 proteins under light stress.
authors.affiliation: Department of Biophysics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, 783 71 Olomouc, Czech Republic.
authors.forename: Ravindra
authors.initials: R
authors.lastname: Kale
authors.affiliation: Department of Biological Sciences, Division of Biochemistry and Molecular Biology, Louisiana State University, Baton Rouge, LA 70803.
authors.forename: Annette E
authors.initials: AE
authors.lastname: Hebert
authors.affiliation: Department of Biological Sciences, Division of Biochemistry and Molecular Biology, Louisiana State University, Baton Rouge, LA 70803.
authors.forename: Laurie K
authors.initials: LK
authors.lastname: Frankel
authors.affiliation: The Rieveschl Laboratories for Mass Spectrometry, Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221.
authors.forename: Larry
authors.initials: L
authors.lastname: Sallans
authors.affiliation: Department of Biological Sciences, Division of Biochemistry and Molecular Biology, Louisiana State University, Baton Rouge, LA 70803; pavel.pospisil@upol.cz btbric@lsu.edu.
authors.forename: Terry M
authors.initials: TM
authors.lastname: Bricker
authors.affiliation: Department of Biophysics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, 783 71 Olomouc, Czech Republic; pavel.pospisil@upol.cz btbric@lsu.edu.
authors.forename: Pavel
authors.initials: P
authors.lastname: Pospíšil
mesh_terms: D000596:Amino Acids / Q000737:chemistry / Q000378:metabolism*; D000975:Antioxidants / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D017665:Hydroxyl Radical / Q000378:metabolism; D013058:Mass Spectrometry; D008958:Models, Molecular; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D000596:Amino Acids; D000975:Antioxidants; D002712:Chlorides; D045332:Photosystem II Protein Complex; D017382:Reactive Oxygen Species; D017665:Hydroxyl Radical; D010100:Oxygen
keywords: Photosystem II; mass spectrometry; photo inhibition; photosynthesis; reactive oxygen species