Formation of superoxide anion and carbon-centered radicals by photosystem II under high light and heat stress-EPR spin-trapping study.
In this study, electron paramagnetic resonance spin-trapping spectroscopy was used to study the light-induced production of superoxide anion (O2 (•-)) and carbon-centered (R(•)) radicals by Photosystem II (PSII). It is evidenced here that exposure of PSII membranes to high light (2,000 μmol photons m(-2) s(-1)) or heat (47 °C) treatments prior to the illumination suppressed O2 (•-) production, while R(•) was formed. Formation of R(•) in the both high light- and heat-treated PSII membranes was enhanced by DCMU. Removal of molecular oxygen by glucose/glucose oxidase/catalase system and O2 (•-) scavenging by exogenous superoxide dismutase completely suppressed carbon-centered radical formation. It is proposed here that the oxidation of polyunsaturated fatty acids and amino acids by O2 (•-) on the electron acceptor side of PSII results in the formation of R(•), known to initiate a cascade reaction leading to the lipid peroxidation and protein degradation, respectively.
Department of Biophysics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Šlechtitelů 11, 783 71, Olomouc, Czech Republic.
Arjun
A
Tiwari
Marek
M
Rác
Pavel
P
Pospíšil
D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry / Q000378:metabolism*; D008027:Light; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism*; D055668:Photochemical Processes; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000378:metabolism*; D019097:Spin Trapping / Q000379:methods*; D018724:Spinacia oleracea; D013481:Superoxides / Q000737:chemistry / Q000378:metabolism*
D005609:Free Radicals; D045332:Photosystem II Protein Complex; D013481:Superoxides; D010100:Oxygen