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- Title
Cyanobacterial photosystem II at 2.9-A resolution and the role of quinones, lipids, channels and chloride.
- Authors
Guskov, Albert; Kern, Jan; Gabdulkhakov, Azat; Broser, Matthias; Zouni, Athina; Saenger, Wolfram
- Abstract
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.
- Publication
Nature structural & molecular biology, 2009, Vol 16, Issue 3, p334
- ISSN
1545-9985
- Publication type
Journal Article
- DOI
10.1038/nsmb.1559