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Transfer of ubiquinol from the reaction center to the bc 1 complex in Rhodobacter sphaeroides chromatophores under oxidizing conditions
Author(s) -
Drachev L.A.,
Mamedov M.D.,
Mulkidjanian A.Ya.,
Semenov A.Yu.,
Shinkarev V.P.,
Verkhovsky M.I.
Publication year - 1989
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(89)80188-7
Subject(s) - photosynthetic reaction centre , rhodobacter sphaeroides , ubiquinol , chemistry , photochemistry , quinone , cytochrome , electron transfer , kinetics , redox , oxidizing agent , electron transport chain , cytochrome c , stereochemistry , coenzyme q – cytochrome c reductase , photosynthesis , inorganic chemistry , biochemistry , organic chemistry , physics , quantum mechanics , mitochondrion , enzyme
The mechanism of interaction between the photosynthetic reaction center (RC) and bc 1 complex has been investigated in chromatophores of Rhodobacter sphaeroides . The kinetics of cytochrome b h reduction and formation of the transmembrane electric potential were measured at high E h , a condition where ubiquinol is formed in the RC only on the second light flash. In the presence of antimycin A, the kinetics of cytochrome b h reduction have been shown to be sensitive neither to the amount of ubiquinol produced nor to the number of active bc 1 complexes. It is concluded that the reaction between the ubiquinol produced on the second flash and the bc 1 complex is monomolecular. To explain the monomolecular pattern of this reaction under oxidizing conditions (the present work) and the previously described bimolecular pattern under reducing conditions [(1983) Biochim. Biophys. Acta 723, 202–218], it is proposed that (i) quinone exchange between the RC and bc 1 complex occurs via a local quinone pool and (ii) the rate of exchange between the quinone pools is very much slower than cytochrome b h reduction.