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    Evidence for Two Distinct Effector-Binding Sites in Threonine Deaminase by Site-Directed Mutagenesis, Kinetic, and Binding Experiments


    Wessel, Peter M. and Graciet, Emmanuelle and Douce, Roland and Dumas, Renaud (2000) Evidence for Two Distinct Effector-Binding Sites in Threonine Deaminase by Site-Directed Mutagenesis, Kinetic, and Binding Experiments. Biochemistry, 39 (49). pp. 15136-15143. ISSN 0006-2960

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    Abstract

    A three-dimensional structure comparison between the dimeric regulatory serine-binding domain of Escherichia coli D-3-phosphoglycerate dehydrogenase [Schuller, D. J., Grant, G. A., and Banaszak, L. J. (1995) Nat. Struct. Biol. 2, 69-76] and the regulatory domain of E. coli threonine deaminase [Gallagher, D. T., Gilliland, G. L., Xiao, G., Zondlo, J., Fisher, K. E., Chinchilla, D. , and Eisenstein, E. (1998) Structure 6, 465-475] led us to make the hypothesis that threonine deaminase could have two binding sites per monomer. To test this hypothesis about the corresponding plant enzyme, site-directed mutagenesis was carried out on the recombinant Arabidopsis thaliana threonine deaminase. Kinetic and binding experiments demonstrated for the first time that each regulatory domain of the monomers of A. thaliana threonine deaminase possesses two different effector-binding sites constituted in part by Y449 and Y543. Our results demonstrate that Y449 belongs to a high-affinity binding site whose interaction with a first isoleucine induces conformational modifications yielding a conformer displaying a higher activity and with enhanced ability to bind a second isoleucine on a lower-affinity binding site containing Y543. Isoleucine interaction with this latter binding site is responsible for conformational modifications leading to final inhibition of the enzyme. Y449 interacts with both regulators, isoleucine and valine. However, interaction of valine with the high-affinity binding site induces different conformational modifications leading to reversal of isoleucine binding and reversal of inhibition.

    Item Type: Article
    Keywords: Effector-Binding Sites; Threonine Deaminase; Site-Directed Mutagenesis; Kinetic; Binding Experiments;
    Academic Unit: Faculty of Science and Engineering > Biology
    Item ID: 7441
    Identification Number: https://doi.org/10.1021/bi001625c
    Depositing User: Emanuelle Graciet
    Date Deposited: 09 Sep 2016 15:12
    Journal or Publication Title: Biochemistry
    Publisher: American Chemical Society
    Refereed: Yes
    URI:

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