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| {{STRUCTURE_1fnq| PDB=1fnq | SCENE= }} | | {{STRUCTURE_1fnq| PDB=1fnq | SCENE= }} |
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| '''CRYSTAL STRUCTURE ANALYSIS OF THE MUTANT REACTION CENTER PRO L209-> GLU FROM THE PHOTOSYNTHETIC PURPLE BACTERIUM RHODOBACTER SPHAEROIDES'''
| | ===CRYSTAL STRUCTURE ANALYSIS OF THE MUTANT REACTION CENTER PRO L209-> GLU FROM THE PHOTOSYNTHETIC PURPLE BACTERIUM RHODOBACTER SPHAEROIDES=== |
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| ==Overview==
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| The structures of the reaction center variants Pro L209 --> Tyr, Pro L209 --> Phe, and Pro L209 --> Glu from the photosynthetic purple bacterium Rhodobacter sphaeroides have been determined by X-ray crystallography to 2.6-2.8 A resolution. These variants were constructed to interrupt a chain of tightly bound water molecules that was assumed to facilitate proton transfer from the cytoplasm to the secondary quinone Q(B) [Baciou, L., and Michel, H. (1995) Biochemistry 34, 7967-7972]. However, the amino acid exchanges Pro L209 --> Tyr and Pro L209 --> Phe do not interrupt the water chain. Both aromatic side chains are oriented away from this water chain and interact with three surrounding polar side chains (Asp L213, Thr L226, and Glu H173) which are displaced by up to 2.6 A. The conformational changes induced by the bulky aromatic rings of Tyr L209 and Phe L209 lead to unexpected displacements of Q(B) compared to the wild-type protein. In the structure of the Pro L209 --> Tyr variant, Q(B) is shifted by approximately 4 A and is now located at a position similar to that reported for the wild-type reaction center after illumination [Stowell, M. H. B., et al. (1997) Science 276, 812-816]. In the Pro L209 --> Phe variant, the electron density map reveals an intermediate Q(B) position between the binding sites of the wild-type protein in the dark and the Pro L209 --> Tyr protein. In the Pro L209 --> Glu reaction center, the carboxylic side chain of Glu L209 is located within the water chain, and the binding site of Q(B) remains unchanged compared to the wild-type structure. | | The line below this paragraph, {{ABSTRACT_PUBMED_11284681}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 11284681 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_11284681}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Michel, H.]] | | [[Category: Michel, H.]] |
| [[Category: Interruption of water chain]] | | [[Category: Interruption of water chain]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 16:32:51 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 03:38:21 2008'' |