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| [[Image:2wsy.gif|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_2wsy| PDB=2wsy | SCENE= }} | | {{STRUCTURE_2wsy| PDB=2wsy | SCENE= }} |
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| '''CRYSTAL STRUCTURE OF WILD-TYPE TRYPTOPHAN SYNTHASE'''
| | ===CRYSTAL STRUCTURE OF WILD-TYPE TRYPTOPHAN SYNTHASE=== |
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| ==Overview==
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| Crystal structures of wild-type tryptophan synthase alpha2beta2 complexes from Salmonella typhimurium were determined to investigate the mechanism of allosteric activation of the alpha-reaction by the aminoacrylate intermediate formed at the beta-active site. Using a flow cell, the aminoacrylate (A-A) intermediate of the beta-reaction () was generated in the crystal under steady state conditions in the presence of serine and the alpha-site inhibitor 5-fluoroindole propanol phosphate (F-IPP). A model for the conformation of the Schiff base between the aminoacrylate and the beta-subunit cofactor pyridoxal phosphate (PLP) is presented. The structure is compared with structures of the enzyme determined in the absence (TRPS) and presence (TRPSF-IPP) of F-IPP. A detailed model for binding of F-IPP to the alpha-subunit is presented. In contrast to findings by Hyde et al. [(1988) J. Biol. Chem. 263,17857-17871] and Rhee et al. [(1997) Biochemistry 36, 7664-7680], we find that the presence of an alpha-site alone ligand is sufficient for loop alphaL6 closure atop the alpha-active site. Part of this loop, alphaThr183, is important not only for positioning the catalytic alphaAsp60 but also for coordinating the concomitant ordering of loop alphaL2 upon F-IPP binding. On the basis of the three structures, a pathway for communication between the alpha- and beta-active sites has been established. The central element of this pathway is a newly defined rigid, but movable, domain that on one side interacts with the alpha-subunit via loop alphaL2 and on the other side with the beta-active site. These findings provide a structural basis for understanding the allosteric properties of tryptophan synthase.
| | The line below this paragraph, {{ABSTRACT_PUBMED_9548921}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 9548921 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_9548921}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Pyridoxal phosphate]] | | [[Category: Pyridoxal phosphate]] |
| [[Category: Tryptophan biosynthesis]] | | [[Category: Tryptophan biosynthesis]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 19:10:41 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 05:44:42 2008'' |
