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РЖ ВИНИТИ 34 (BI12) 96.02-04Б2.11

Baciou, Laura.
Interruption of the water chain in the reaction center from Rhodobacter sphaeroides reduces the rates of the proton uptake and of the second electron transfer to Q[B] [Text] / Laura Baciou, Hartmut Michel // Biochemistry. - 1995. - Vol. 34, N 25. - P7972 . - ISSN 0006-2960
Перевод заглавия: Разрыв водных цепочек в реакционном центре Rhodobacter sphaeroides восстанавливает скорость поглощения протона и вторичного переноса электрона к Q{+}[B]
Аннотация: A chain of bound water molecules was recently identified in the photosynthetic reaction center (RC) from Rhodobacter sphaeroides by X-ray crystallography [Ermler et al. (1994) Structure 2, 925-936]. The possible role of the chain in proton transfer from the solution to the secondary quinone (Q[B]) was investigated by site-directed mutagenesis and flash-induced absorbance spectroscopy. Pro L209, situated along the water chain about 9 A from Q[B], was changed into the aromatic residues Phe and Tyr in order to interrupt the chain. In the PL209Y (Pro L209'-'Tyr) mutant, the very small changes in the Q{-}[A]Q[B]'-'Q[A]Q{-}[B] equilibrium constant (K[2]) and the first electron-transfer rates (k[AB]{(1)}) indicate that the mutation does not lead to large structural changes. In the PL209F (Pro L209'-'Phe) mutant, a 7-fold decrease of k[AB]{(1)} is observed. It follows a pH dependence parallel to that of the wild type. It is consistent with no modification of the pK of the Glu L212 determined from the pH dependence of K[2]. The decreased k[AB]{(1)} may reflect some slight structural modification in this mutant and/or rearrangement of the cluster of charged residues close to the L209 position. The major effect of the mutations observed is a concomitant decrease of the rates of the second electron transfer, k[AB]{(2)}, and of the proton uptake upon the second flash. The relative decrease of the k[AB]{(2)} rate values in the mutants is more pronounced above pH 8. Our results indicate that the mutations have specifically altered the pathway of proton transfer to Q[B]. We propose that in the wild type the chain of bound water molecules provides the most efficient pathway for the proton transfer from cytoplasm to the close vicinity of Q[B]. This pattern might be a common behavior in proton-translocating membrane proteins. Германия, Max-Planck-Inst. Biophys., Heinrich Hoffmann-Str. 7, D-60528 Frankfurt/Main. Библ. 28

ГРНТИ	34.27.17

ВИНИТИ 341.27.17.09.07.07.07
Рубрики: РЕАКЦИОННЫЕ ЦЕНТРЫ
РАЗРЫВ ВОДНЫХ ЦЕПОЧЕК
ПРОТОНЫ
ПОГЛОЩЕНИЕ
ЭЛЕКТРОННЫЙ ТРАНСПОРТ
RHODOBACTER SPHAEROIDES

Доп.точки доступа:
Michel, Hartmut

"Электронные каталоги и базы данных библиотек СО РАН"

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