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Cyanobacterial photosystem II at 2.9-Ă… resolution and the role of quinones, lipids, channels and chloride.
- Source :
-
Nature Structural & Molecular Biology . Mar2009, Vol. 16 Issue 3, p334-342. 9p. 5 Diagrams, 1 Chart. - Publication Year :
- 2009
-
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-Šresolution 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 QC 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 Mn4Ca cluster at a distance of 6.5 Šand is close to two possible proton channels. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 15459993
- Volume :
- 16
- Issue :
- 3
- Database :
- Academic Search Index
- Journal :
- Nature Structural & Molecular Biology
- Publication Type :
- Academic Journal
- Accession number :
- 36792751
- Full Text :
- https://doi.org/10.1038/nsmb.1559