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Loop closure and intersubunit communication in tryptophan synthase.
Biochemistry. 1998 Apr 21; 37(16):5394-406.B

Abstract

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.

Authors+Show Affiliations

Schneider TR
Department for Physical Biochemistry, Max-Planck-Institute for Molecular Physiology, Dortmund, Germany.
Gerhardt E
No affiliation info available
Lee M
No affiliation info available
Liang PH
No affiliation info available
Anderson KS
No affiliation info available
Schlichting I
No affiliation info available

MeSH

AlanineAllosteric SiteCrystallography, X-RayEnzyme ActivationLigandsModels, MolecularProtein Structure, SecondaryProtein Structure, TertiarySalmonella typhimuriumSerineStructure-Activity RelationshipTryptophan Synthase

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

9548921

Citation

Schneider, T R., et al. "Loop Closure and Intersubunit Communication in Tryptophan Synthase." Biochemistry, vol. 37, no. 16, 1998, pp. 5394-406.
Schneider TR, Gerhardt E, Lee M, et al. Loop closure and intersubunit communication in tryptophan synthase. Biochemistry. 1998;37(16):5394-406.
Schneider, T. R., Gerhardt, E., Lee, M., Liang, P. H., Anderson, K. S., & Schlichting, I. (1998). Loop closure and intersubunit communication in tryptophan synthase. Biochemistry, 37(16), 5394-406.
Schneider TR, et al. Loop Closure and Intersubunit Communication in Tryptophan Synthase. Biochemistry. 1998 Apr 21;37(16):5394-406. PubMed PMID: 9548921.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Loop closure and intersubunit communication in tryptophan synthase. AU - Schneider,T R, AU - Gerhardt,E, AU - Lee,M, AU - Liang,P H, AU - Anderson,K S, AU - Schlichting,I, PY - 1998/5/16/pubmed PY - 1998/5/16/medline PY - 1998/5/16/entrez SP - 5394 EP - 406 JF - Biochemistry JO - Biochemistry VL - 37 IS - 16 N2 - 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. SN - 0006-2960 UR - https://www.unboundmedicine.com/medline/citation/9548921/Loop_closure_and_intersubunit_communication_in_tryptophan_synthase_ L2 - https://doi.org/10.1021/bi9728957 DB - PRIME DP - Unbound Medicine ER -
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