Steady-state cyclic electron transfer through solubilized Rhodobacter sphaeroides reaction centres

van Rotterdam, BartLund University,Lunds universitet,Biokemi och Strukturbiologi,Centrum för Molekylär Proteinvetenskap,Kemiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,Biochemistry and Structural Biology,Center for Molecular Protein Science,Department of Chemistry,Departments at LTH,Faculty of Engineering, LTH (author)

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.

Westerhoff, Hans V (author)
Visschers, Ronald W (author)
Jones, Michael R (author)
Hellingwerf, Klaas J (author)
Crielaard, Wim (author)
Biokemi och StrukturbiologiCentrum för Molekylär Proteinvetenskap (creator_code:org_t)

By the author/editor: van Rotterdam, B ...; Westerhoff, Hans ...; Visschers, Ronal ...; Jones, Michael R; Hellingwerf, Kla ...; Crielaard, Wim

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