Publications

• The role of plastoquinone and beta-carotene in the primary reaction of plant photosystem II.

  Knaff D.B., Malkin R., Myron J.C., Stoller M.

  Extraction of Triton Photosystem II chloroplast fragments with 0.2% methanol in hexane for 3 h results in the removal of 90 to 95% of the plastoquinone in the original preparation. The extracted fragments (chlorophyll:plastoquinone ratio, 900: 1) showed no P-680 photooxidation at 15 K after a sing ... >> More

  Extraction of Triton Photosystem II chloroplast fragments with 0.2% methanol in hexane for 3 h results in the removal of 90 to 95% of the plastoquinone in the original preparation. The extracted fragments (chlorophyll:plastoquinone ratio, 900: 1) showed no P-680 photooxidation at 15 K after a single laser flash. The extracted fragments also showed no light-induced C-550 absorbance change at 77 K. Reconstitution of the primary reaction of Photosystem II, as evidenced by restoration of low-temperature photooxidation of P-680, could be obtained by the addition of plastoquinone A but not by the addition of beta-carotene. The addition of beta-carotene plus plastoquinone A restored the C-550 absorbance change. These results indicate that plastoquinone functions as the primary electron acceptor of Photosystem II and that beta-carotene does not play a direct role in the primary photochemistry but is required for the C-550 absorbance change. << Less

  Biochim Biophys Acta 459:402-411(1977) [PubMed] [EuropePMC]

• Cyanobacterial photosystem II at 2.9-A resolution and the role of quinones, lipids, channels and chloride.

  Guskov A., Kern J., Gabdulkhakov A., Broser M., Zouni A., Saenger W.

  Photosystem II (PSII) is a large homodimeric protein-cofactor complex located in the photosynthetic thylakoid membrane that acts as light-driven water:plastoquinone oxidoreductase. The crystal structure of PSII from Thermosynechococcus elongatus at 2.9-A resolution allowed the unambiguous assignme ... >> More

  Photosystem II (PSII) is a large homodimeric protein-cofactor complex located in the photosynthetic thylakoid membrane that acts as light-driven water:plastoquinone oxidoreductase. The crystal structure of PSII from Thermosynechococcus elongatus at 2.9-A resolution allowed the unambiguous assignment of all 20 protein subunits and complete modeling of all 35 chlorophyll a molecules and 12 carotenoid molecules, 25 integral lipids and 1 chloride ion per monomer. The presence of a third plastoquinone Q(C) and a second plastoquinone-transfer channel, which were not observed before, suggests mechanisms for plastoquinol-plastoquinone exchange, and we calculated other possible water or dioxygen and proton channels. Putative oxygen positions obtained from a Xenon derivative indicate a role for lipids in oxygen diffusion to the cytoplasmic side of PSII. The chloride position suggests a role in proton-transfer reactions because it is bound through a putative water molecule to the Mn(4)Ca cluster at a distance of 6.5 A and is close to two possible proton channels. << Less

  Nat. Struct. Mol. Biol. 16:334-342(2009) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.