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The Q o ‐site inhibitor DBMIB favours the proximal position of the chloroplast Rieske protein and induces a p K ‐shift of the redox‐linked proton
Author(s) -
Schoepp Barbara,
Brugna Myriam,
Riedel Astrid,
Nitschke Wolfgang,
Kramer David M.
Publication year - 1999
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/s0014-5793(99)00511-6
Subject(s) - chemistry , redox , cytochrome b6f complex , crystallography , cluster (spacecraft) , photochemistry , photosystem ii , photosystem i , photosynthesis , inorganic chemistry , biochemistry , computer science , programming language
The interaction of the inhibitor 2,5‐dibromo‐3‐methyl‐6‐isopropylbenzoquinone (DBMIB) with the Rieske protein of the chloroplast b 6 f complex has been studied by EPR. All three redox states of DBMIB were found to interact with the iron‐sulphur cluster. The presence of the oxidised form of DBMIB altered the equilibrium distribution of the Rieske protein's conformational substates, strongly favouring the proximal position close to heme b L . In addition to this conformational effect, DBMIB shifted the p K ‐value of the redox‐linked proton involved in the iron‐sulphur cluster's redox transition by about 1.5 pH units towards more acidic values. The implications of these results with respect to the interaction of the native quinone substrate and the Rieske cluster in cytochrome bc complexes are discussed.