Electron transfers amongst cytochrome f, plastocyanin and photosystem I: kinetics and mechanisms.
The review covers the theory and practice of the determination of kinetic constants for the electron transfer reactions in chloroplast thylakoid membranes between plastocyanin and cytochrome f in cytochrome bf complexes, and between plastocyanin and the reaction centre of photosystem I. Effects of ionic strength and pH are featured. The contribution of mutant studies is included. It is concluded that nearly all data from in vitro experiments can be interpreted with a reaction scheme in which an encounter complex between donor and acceptor is formed by long-range electrostatic attraction, followed by rearrangement during which metal centres become close enough for rapid intra-complex electron transfer. In vivo experiments so far cast doubt on this particular sequence, but their interpretation is not straightforward. Means of modelling the bimolecular complex between cytochrome f and plastocyanin are outlined, and two likely structures are illustrated. The complex formed by plastocyanin and photosystem I in higher plants involves the PsaF subunit, but its structure has not been fully determined.
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School of Biological Sciences, Faculty of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, SA, Australia. alex.hope@flinders.edu.au
D002734:Chlorophyll / Q000737:chemistry; D003580:Cytochromes / Q000737:chemistry*; D045348:Cytochromes f; D004579:Electron Transport; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D009994:Osmolar Concentration; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D045331:Photosystem I Protein Complex; D010970:Plastocyanin / Q000737:chemistry*; D055672:Static Electricity; D020524:Thylakoids / Q000737:chemistry
D003580:Cytochromes; D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D002734:Chlorophyll; C001785:chlorophyll P 700; D010970:Plastocyanin; D045348:Cytochromes f