Recombination Reduction of Photooxidized Cytochrome c in Reaction Centers of Rhodopseudomonas viridis at Low Temperature

S. K. Chamorovsky, E. P. Lukashev^*, P. P. Knox, N. I. Zakharova, and N. Kh. Seifullina

School of Biology, Lomonosov Moscow State University, Moscow, 119899 Russia; fax: (095) 939-1115; E-mail: serch@bioh.phys.msu.su; lukashev@biophys.msu.ru; knox@biophys.msu.ru

^* To whom correspondence should be addressed.

Received December 5, 2000; Revision received March 2, 2001

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The temperature dependence of dark reduction of photooxidized cytochrome c was studied in isolated preparations of Rhodopseudomonas viridis reaction centers. Within the range from room temperature to ~260 K this process was found to be mediated by thermal diffusion of exogenous donor molecules, whereas at lower temperatures photooxidized cytochrome is reduced as a result of indirect recombination with photoreduced primary quinone acceptor. Kinetic simulation allowed certain thermodynamic characteristics of this reaction to be calculated. To the first approximation, these characteristics correlate with the estimates obtained from the results of direct redox titration.

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KEY WORDS: photosynthetic reaction center, cytochromes, electron transport, recombination, purple bacteria

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