Cyanobacterial Photosystem II at 3.2 Å resolution - the plastoquinone binding pockets
| Autor: | Klaus-Dieter Irrgang, Jan Kern, Jacek Biesiadka, Bernhard Loll, Athina Zouni, Wolfram Saenger |
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| Rok vydání: | 2005 |
| Předmět: |
Models
Molecular Photosystem II Plastoquinone Protein Conformation Plant Science Cyanobacteria Thylakoids Biochemistry Purple bacteria chemistry.chemical_compound Protein structure Binding site Binding Sites Molecular mass biology Chemistry Photosystem II Protein Complex Cell Biology General Medicine biology.organism_classification Anoxygenic photosynthesis Protein Subunits Crystallography Thylakoid Protein Binding |
| Zdroj: | Photosynthesis Research |
| ISSN: | 1573-5079 0166-8595 |
| Popis: | Photosystem II from thylakoid membranes of the thermophilic cyanobacterium Thermosynechococcus elongatus was solubilized with n-beta-dodecylmaltoside and purified using anion exchange chromatography. Molecular weight, pigment stoichiometry and subunit composition were assayed using various techniques. The holocomplex is dimeric with a molecular mass of 756 +/- 18 kDa and functionally fully active. Crystals obtained from these samples showed significantly improved quality leading to a 3D structure at 3.2 A resolution. Several loop regions of the principal protein subunits are now defined that were not interpretable at lower (3.8 A) resolution, thus resulting in a more complete model. The head groups of the cofactors of the electron transfer chain and of the antennae have been modeled, coordinating and hydrogen bonding amino acids identified and the nature of the binding pockets derived. The orientations of these cofactors resemble those of the reaction centre from anoxygenic purple bacteria. For the two plastoquinones, electron density was only found for the head group of QA and none for QB indicating low or even no occupancy of this site in the crystal structure. Both binding pockets and problems related to the QB site are discussed here and compared to the situation in the purple bacterial reaction centre. |
| Databáze: | OpenAIRE |
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