Steady-state cyclic electron transfer through solubilized Rhodobacter sphaeroides reaction centers.

B.J. van Rotterdam, R.W. Visschers, H.V. Westerhoff, W. Crielaard, K.J. Hellingwerf

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

The mechanism, thermodynamics and kinetics of light-induced cyclic electron transfer have been studied in a model energy-transducing system consisting of solubilized Rhodobacter sphaeroides reaction center/light harvesting-1 complexes (so-called core complexes), horse heart cytochrome c and a ubiquinone-0/ubiquinol-0 pool. An analysis of the steady-state kinetics of cytochrome c reduction by ubiquinol-0, after a light-induced steady-state electron flow had been attained, showed that the rate of this reaction is primarily controlled by the one-electron oxidation of the ubiquinol-anion. Re-reduction of the light-oxidized reaction center primary donor by cytochrome c was measured at different reduction levels of the ubiquinone-0/ubiquinol-0 pool. These experiments involved single turnover flash excitation on top of background illumination that elicited steady-state cyclic electron transfer. At low reduction levels of the ubiquinone-0/ubiquinol-0 pool, the total cytochrome c concentration had a major control over the rate of reduction of the primary donor. This control was lost at higher reduction levels of the ubiquinone/ubiquinol-pool, and possible reasons for this behaviour are discussed. (C) 2000 Elsevier Science B.V.
Original languageEnglish
Pages (from-to)137-152
JournalBiophysical Chemistry
Volume88
DOIs
Publication statusPublished - 2000

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