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Research article2009Peer reviewedOpen access

Structural Basis for the Inhibition of Mycobacterium tuberculosis Glutamine Synthetase by Novel ATP-Competitive Inhibitors

Nilsson, MT; Krajewski, WW; Yellagunda, S; Prabhumurthy, ; Chamarahally, Gayathri N.; Siddamadappa, Chandrasekharan; Srinivasa, BR; Yahiaoui, S; Larhed, M; Karlén, Anders; Jones, TA; Mowbray, Sherry


Glutamine synthetase (GS, EC; also known as gamma-glutamyl:ammonia ligase) catalyzes the ATP-dependent condensation of glutamate and ammonia to form glutamine. The enzyme has essential roles in different tissues and species, which have led to its consideration as a drug or an herbicide target. In this article, we describe studies aimed at the discovery of new antimicrobial agents targeting Mycobacterium tuberculosis, the causative pathogen of tuberculosis. A number of distinct classes of GS inhibitors with an IC(50) of micromolar value or better were identified via high-throughput screening. A commercially available purine analogue similar to one of the clusters identified (the diketopurines), 1-[(3,4-dichlorophenyl)methyl]-3,7-dimethyl-8-morpholin-4-yl-purine-2,6-dione, was also shown to inhibit the enzyme, with a measured IC(50) of 2.5+/-0.4 mu M. Two X-ray structures are presented: one is a complex of the enzyme with the purine analogue alone (2.55-angstrom resolution), and the other includes the compound together with methionine sulfoximine phosphate, magnesium and phosphate (2.2-angstrom resolution). The former represents a relaxed, inactive conformation of the enzyme, while the latter is a taut, active one. These structures show that the compound binds at the same position in the nucleotide site, regardless of the conformational state. The ATP-binding site of the human enzyme differs substantially, explaining why it has an similar to 60-fold lower affinity for this compound than the bacterial GS. As part of this work, we devised a new synthetic procedure for generating L-(SR)-methionine sulfoximine phosphate from L-(SR)-methionine sulfoximine, which will facilitate future investigations of novel GS inhibitors. (C) 2009 Elsevier Ltd. All rights reserved.


glutamine synthetase; X-ray crystallography; high-throughput screening; drug design; tuberculosis

Published in

Journal of Molecular Biology
2009, Volume: 393, number: 2, pages: 504-513

      SLU Authors

    • Mowbray, Sherry

      • Department of Molecular Biology, Swedish University of Agricultural Sciences

    Sustainable Development Goals

    SDG3 Good health and well-being

    UKÄ Subject classification

    Biochemistry and Molecular Biology

    Publication identifier


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