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          Institute: MPI für medizinische Forschung     Collection: Abteilung Biomolekulare Mechanismen     Display Documents

ID: 22599.0, MPI für medizinische Forschung / Abteilung Biomolekulare Mechanismen
Loop closure and intersubunit communication in tryptophan synthase
Translation of Title:Loop closure and intersubunit communication in tryptophan synthase
Authors:Schneider, T. R.; Gerhardt, E.; Lee, M.; Liang, P. H.; Anderson, K. S.; Schlichting, Ilme
Date of Publication (YYYY-MM-DD):1998-04-21
Title of Journal:Biochemistry
Journal Abbrev.:Biochem.
Issue / Number:16
Start Page:5394
End Page:5406
Review Status:Peer-review
Audience:Experts Only
Intended Educational Use:No
Abstract / Description:Crystal structures of wild-type tryptophan synthase α2β2 complexes from Salmonella typhimurium were determined to investigate the mechanism of allosteric activation of the α-reaction by the aminoacrylate intermediate formed at the β-active site. Using a flow cell, the aminoacrylate (A-A) intermediate of the β-reaction () was generated in the crystal under steady state conditions in the presence of serine and the α-site inhibitor 5-fluoroindole propanol phosphate (F-IPP). A model for the conformation of the Schiff base between the aminoacrylate and the β-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 α-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 α-site alone ligand is sufficient for loop αL6 closure atop the α-active site. Part of this loop, αThr183, is important not only for positioning the catalytic αAsp60 but also for coordinating the concomitant ordering of loop αL2 upon F-IPP binding. On the basis of the three structures, a pathway for communication between the α- and β-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 α-subunit via loop αL2 and on the other side with the β-active site. These findings provide a structural basis for understanding the allosteric properties of tryptophan synthase.
External Publication Status:published
Document Type:Article
Communicated by:Wulf Kaiser
Affiliations:MPI für medizinische Forschung/Abteilung Biomolekulare Mechanismen/
Identifiers:URI:http://pubs.acs.org/journals/bichaw/article.cgi/bi... [Full text]
URI:http://pubs.acs.org/journals/bichaw/abstract.cgi/b... [Abstract]
URI:http://pubs.acs.org/journals/bichaw/article.cgi/bi... [Fulltext PDF]
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