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Oxygen‐induced changes in the redox state of the cytochrome b 559 in photosystem II depend on the integrity of the Mn cluster
Author(s) -
Mamedov Fikret,
Gadjieva Rena,
Styring Stenbjörn
Publication year - 2007
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.2007.00938.x
Subject(s) - redox , chemistry , photosystem ii , oxygen , tris , membrane , cytochrome , spinach , oxygen evolution , biophysics , membrane potential , electron transport chain , oxygen evolving complex , photochemistry , photosynthesis , biochemistry , inorganic chemistry , biology , enzyme , electrochemistry , organic chemistry , electrode
The effect of oxygen and anaerobiosis on the redox properties of Cyt b 559 was investigated in PSII preparations from spinach with different degree of disintegration of the donor side. Comparative studies were performed on intact PSII membranes and PSII membranes that were deprived of the 18‐kDa peripheral subunit (0.25 NaCl washed), the 18‐ and 24‐kDa peripheral subunits (1 M NaCl washed), the 18‐, 24‐ and 33‐kDa peripheral subunits (1.2 M CaCl 2 washed), Cl depleted and after complete depletion of the Mn cluster (Tris washed). In active PSII centers, about 75% of Cyt b 559 was found in the high‐potential form and the rest in the intermediate potential form. With decomposition of the donor side, the intermediate potential form started to dominate, reaching more than 90% after Tris treatment. The oxygen‐dependent conversion of the intermediate potential form of Cyt b 559 into the low‐potential and high‐potential forms was only observed after treatments that directly affect the Mn cluster. In PSII membranes, deprived of all three extrinsic subunits (CaCl 2 treatment), 21% of the intermediate potential form was converted into the low‐potential form and 14% into the high‐potential form by the removal of oxygen. In Tris‐washed PSII membranes, completely lacking the Mn cluster, this conversion amounted to 60 and 33%, respectively. In intact PSII membranes, the oxygen‐dependent conversion did not occur. The possible physiological role of this oxygen‐dependent behavior of the Cyt b 559 redox forms during the assembly/photoactivation cycle of PSII is discussed.