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The processes of electron transfer in cyanobacterial photosystem I (PS I) and photoelectric methods of the studies were reviewed. Particular emphasis was placed on structural and kinetic characteristics of the electron transport chain. The electrogenicity in PS I complex and its interaction with natural donors (plastocyanin, cytochrome c6), natural acceptors (ferredoxin, flavodoxin), and artificial acceptors and donors (methyl viologen and other redox dyes) were studied. On the basis of photoelectric measurements and the X-ray structural data, the operating dielectric constants in the vicinity of charge carriers in situ were calculated. The profile of distribution of the dielectric constant along the PS I pigment-protein complex (from plastocyanin or cytochrome c6 through the chlorophyll dimer P700 to the acceptor complex) was estimated, and possible mechanisms of correlation between the local dielectric constant and the electron transfer rate constant in the corresponding segment of the chain were discussed.

By using the direct electrometric technique, the flash-induced generation of the difference in electrical potentials in hybrid proteoliposomes containing photosystem 1 and cytochrome bf complexes from cyanobacteria Synechocystis sp. PCC 6803 was studied. It was shown that the primary donor P700 in photosystem I and cytochrome f are predominantly localized near the outer surface of the proteoliposomal membrane, which made it possible to study for the first time electrogenic reactions of cytochrome bf complexes in a model system. In the presence of decyl plastoquinol and cytochrome c6, besides the fast electrogenic phase determined by the separation of charges in photosystem I, additional electrogenic phases in the submillisecond and millisecond ranges were observed. These phases were partially depressed in the presence of the inhibitor of the plastoquinone reductase site NQNO and fully disappeared after the addition of the inhibitor of the plastoquinol oxidase site stigmatellin. A possible mechanism of the electrogenic reactions in cytochrome bf complexes was considered.

The effects of glycerolipids from thylakoid membranes on the electron transport and proton-translocating activities of the cytochrome bf complex from spinach have been studied. When the cytochrome bf complex was mixed with the lipids from the wild type of Synechocystis PCC6803 containing mono-, di- and triunsaturated lipid molecules, the activity of the electron transport was stimulated by DGDG and PG, but not by MGDG and SQDG. Essentially the same effect, though less significant, was observed with lipids from a desaturation mutant containing only monounsaturated lipid molecules. At the same time, none of these lipids activated the proton translocation function. The highest proton-translocating activities were observed in mixtures of these lipids. No activity of proton translocation was found, however, when the cytochrome bf complex was mixed with the mutant strain lipids. It may thus be concluded that polyunsaturated lipid molecules are obligately required for the activity of proton translocation, while they have a negligible stimulating effect on the oxidoreductase activity.