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  On the role of αThr183 in the allosteric regulation and catalytic mechanism of tryptophan synthase

Kulik, V., Weyand, M., Seidel, R., Niks, D., Arac, D., Dunn, M. F., et al. (2002). On the role of αThr183 in the allosteric regulation and catalytic mechanism of tryptophan synthase. Journal of Molecular Biology, 324(4): 1, pp. 677-690. Retrieved from http://dx.doi.org/10.1016/S0022-2836(02)01109-9.

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Genre: Journal Article
Alternative Title : J. Mol. Biol.

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 Creators:
Kulik, Victor1, Author
Weyand, Michael1, Author
Seidel, Ralf2, Author           
Niks, Dimitri, Author
Arac, Demet, Author
Dunn, Michael F., Author
Schlichting, Ilme2, Author           
Affiliations:
1Max Planck Institute of Molecular Physiology, Max Planck Society, ou_1753286              
2Abt. III: Physikalische Biochemie, Max Planck Institute of Molecular Physiology, Max Planck Society, ou_1753289              

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Free keywords: tryptophan synthase; loop closure; pyroxidal phosphate; crystal structure; allosteric communication
 Abstract: The catalytic activity and substrate channeling of the pyridoxal 5'-phosphate-dependent tryptophan synthase alpha(2)beta(2) complex is regulated by allosteric interactions that modulate the switching of the enzyme between open, low activity and closed, high activity states during the catalytic cycle. The highly conserved alphaThr183 residue is part of loop alphaL6 and is located next to the alpha-active site and forms part of the alpha-beta subunit interface. The role of the interactions of alphaThr183 in alpha-site catalysis and I allosteric regulation was investigated by analyzing the kinetics and crystal structures of the isosteric mutant alphaThr183Val. The mutant displays strongly impaired allosteric alpha-beta communication, and the catalytic activity of the alpha-reaction is reduced one hundred fold, whereas the beta-activity is not affected. The structural work establishes that the basis for the missing inter-subunit signaling is the lack of loop alphaL6 closure even in the presence of the alpha- subunit ligands, 3-indolyl-D-glycerol 3'-phosphate, or 3- indolylpropanol 3'-phosphate. The structural basis for the reduced alpha-activity has its origins in the missing hydrogen bond between aThr183 and the catalytic residue, alphaAsp60. (C) 2002 Elsevier Science Ltd. All rights reserved.

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Language(s): eng - English
 Dates: 2002-11-26
 Publication Status: Issued
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: eDoc: 10686
URI: http://dx.doi.org/10.1016/S0022-2836(02)01109-9
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Title: Journal of Molecular Biology
  Alternative Title : J. Mol. Biol.
Source Genre: Journal
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Pages: - Volume / Issue: 324 (4) Sequence Number: 1 Start / End Page: 677 - 690 Identifier: -