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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., Mar-2009, In : Nature Structural & Molecular Biology. 16, 3, p. 334-342 9 p.

Research output: Contribution to journalArticleAcademicpeer-review

  • Albert Guskov
  • Jan Kern
  • Azat Gabdulkhakov
  • Matthias Broser
  • Athina Zouni
  • Wolfram Saenger

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.

Original languageEnglish
Pages (from-to)334-342
Number of pages9
JournalNature Structural & Molecular Biology
Volume16
Issue number3
Publication statusPublished - Mar-2009

    Keywords

  • Bacterial Proteins, Binding Sites, Chlorides, Crystallography, X-Ray, Cyanobacteria, Lipids, Models, Molecular, Photosystem II Protein Complex, Protein Structure, Quaternary, Protein Subunits, Quinones

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