Electrogenicity at the secondary quinone acceptor site of cyanobacterial photosystem II.
Flash-induced generation of the electric potential difference (delta psi) by a direct electrometrical method was studied in Anacystis nidulans photosystem II-containing proteoliposomes associated with a phospholipid-impregnated collodion film. Besides a rapid phase of delta psi generation corresponding to charge separation between P680 and QA, an additional electrogenic phase with a characteristic time of 0.27 ms at pH 7.0 was observed after the second laser flash. The maximal amplitude of this phase was approx. 4% of that related to the P680+QA- formation. The sensitivity of this phase to DCMU, the flash-number dependence of its amplitude as well as the amplitude and the rate constant pH-dependences, indicate that it is due to the dismutation of QA- and QB- and to subsequent protonation of a doubly reduced plastoquinone QB2-.
Mamedov
M D
MD
Department of Cell Physiology and Immunology, School of Biology, Moscow State University, Russian Federation.
Beshta
O E
OE
Samuilov
V D
VD
Semenov AYu
D000458:Cyanobacteria / Q000737:chemistry*; D004563:Electrochemistry; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D011510:Proteolipids / Q000737:chemistry; D011809:Quinones / Q000737:chemistry*
D045322:Photosynthetic Reaction Center Complex Proteins; D011510:Proteolipids; D011809:Quinones; C020485:proteoliposomes