Characterization of singlet oxygen production and its involvement in photodamage of Photosystem II in the cyanobacterium Synechocystis PCC 6803 by histidine-mediated chemical trapping

Rehman, Ateeq Ur and Cser, Krisztián and Sass, László and Vass, Imre (2013) Characterization of singlet oxygen production and its involvement in photodamage of Photosystem II in the cyanobacterium Synechocystis PCC 6803 by histidine-mediated chemical trapping. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, 1827 (6). pp. 689-698. ISSN 0005-2728

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Abstract

Singlet oxygen production in intact cells of the cynobacterium Synechocystis 6803 was studied using chemical trapping by histidine, which leads to O-2 uptake during illumination. The rate of O-2 uptake, measured by a standard Clark-type electrode, is enhanced in the presence of D2O, which increases the lifetime of O-1(2), and suppressed by the O-1(2) quencher NaN3. Due to the limited mobility of O-1(2) these data demonstrate that exogenous histidine reaches close vicinity of O-1(2) production sites inside the cells. Flash induced chlorophyll fluorescence measurements showed that histidine does not inhibit Photosystem II activity up to 5 mM concentration. By applying the histidine-mediated O-2 uptake method we showed that O-1(2) production linearly increases with light intensity even above the saturation of photosynthesis. We also studied O-1(2) production in site directed mutants in which the Gln residue at the 130th position of the D1 reaction center subunit was changed to either Glu or Leu, which affect the efficiency of nonradiative charge recombination from the primary radical pair (Rappaport et al. 2002, Biochemistry 41: 8518-8527; Cser and Vass 2007, BBA 1767:233-243). We found that the D1-Gln130Glu mutant showed decreased O-1(2) production concomitant with decreased rate of photodamage relative to the WT, whereas both O-1(2) production and photodamage were enhanced in the D1-Gln130Leu mutant. The data are discussed in the framework of the model of photoinhibition in which (3)P680 mediated O-1(2) production plays a key role in PSII photodamage, and nonradiative charge recombination of the primary charge separated state provides a photoprotective pathway. (c) 2013 Elsevier B.V. All rights reserved.

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