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Interaction of the high‐spin Fe atom in the photosystem II reaction center with the quinones Q A and Q B in purified oxygen‐evolving PS II reaction center complex and in PS II particles
Author(s) -
Itoh Shigeru,
Tang Xiao-Song,
Satoh Kimiyuki
Publication year - 1986
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(86)80912-7
Subject(s) - dcmu , photosystem ii , photosynthetic reaction centre , electron paramagnetic resonance , chemistry , photochemistry , phenanthroline , oxygen evolution , crystallography , ligand (biochemistry) , acceptor , quinone , spin trapping , tricine , oxidizing agent , oxygen evolving complex , electron transfer , radical , stereochemistry , photosynthesis , nuclear magnetic resonance , biochemistry , physics , receptor , electrode , organic chemistry , electrochemistry , condensed matter physics
EPR signals in the high‐spin region were studied at 10 K in photosystem II (PS II) particles and in a purified oxygen‐evolving PS II reaction center complex under oxidizing conditions. PS II particles showed EPR peaks at g = 8.0 and 5.6, confirming the recent report by Petrouleas and Diner [(1986) Biochim. Biophys. Acta 849, 264‐275]. Addition of 3‐(3',4'‐dichlorophenyl)‐1,1‐dimethylurea (DCMU) or o ‐phenanthroline shifted the peaks to be closer to g = 6.0 depending on the medium pH. On the other hand, the PS II reaction center complex showed peaks at g = 6.1 and 7.8, and at g = 6.1 and 6.4, in the absence and presence of o ‐phenanthroline, respectively. All these peaks were found to be decreased by the illumination at 10 K. These results suggest that the high‐spin signals are due to Q 400 , Fe(III) atom interacting with the PS II primary electron acceptor quinone Q A as reported and that the Fe atom also interacts with the secondary acceptor quinone Q B . This interaction seems to induce the highly asymmetric ligand coordination of the Fe atom and to be affected by DCMU and o ‐phenanthroline in a somewhat different manner.