Electrogenic reduction of the primary electron donor P700 + in photosystem I by redox dyes

• Published in: FEBS letters 1997-09, Vol.414 (2), p.193-196
• Main Authors: Gourovskaya, Kira N., Mamedov, Mahir D., Vassiliev, Ilya R., Golbeck, John H., Semenov, Alexey Yu
• Format: Article
• Language: English
• Subjects: 2,6-Dichloroindophenol - pharmacology; Chlorophyll - metabolism; Coloring Agents; Cyanobacteria - metabolism; Electrochemistry - methods; Electrogenic phase; Electron Transport - drug effects; Kinetics; Light-Harvesting Protein Complexes; Liposomes; Membrane Potentials; Methylphenazonium Methosulfate - pharmacology; Oxidation-Reduction; Photoelectric response; Photosynthetic Reaction Center Complex Proteins - drug effects; Photosynthetic Reaction Center Complex Proteins - metabolism; Photosystem I; Photosystem I Protein Complex; Proteolipids - metabolism; Proteoliposome; Redox dye; Synechocystis sp. PCC 6803; Tetramethylphenylenediamine - pharmacology; Time Factors
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/S0014-5793(97)00994-0

The kinetics of reduction of the photo-oxidized primary electron donor P700 + by redox dyes N,N,N′, N′-tetramethyl- p-phenylendiamine, 2,6-dichlorophenol-indophenol and phenazine methosulfate was studied in proteoliposomes containing Photosystem I complexes from cyanobacteria Synechocystis sp. PCC 6803 using direct electrometrical technique. In the presence of high concentrations of redox dyes, the fast generation of a membrane potential related to electron transfer between P700 and the terminal iron-sulfur clusters F A/F B was followed by a new electrogenic phase in the millisecond time domain, which contributes approximately 20% to the overall photoelectric response. This phase is ascribed to the vectorial transfer of an electron from the redox dye to the protein-embedded chlorophyll of P700 +. Since the contribution of this electrogenic phase in the presence of artificial redox dyes is approximately equal to that of the phase observed earlier in the presence of cytochrome c 6, it is likely that electrogenic reduction of P700 + in vivo occurs due to vectorial electron transfer within RC molecule rather than within the cytochrome c 6-P700 complex.