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Crystal structure of Mycobacterium Tuberculosis Glutamine Synthetase in complex with a purine analogue inhibitor and L-methionine-S- sulfoximine phosphate.
Structural highlights
FunctionGLN1B_MYCTU Involved in nitrogen metabolism via ammonium assimilation. Catalyzes the ATP-dependent biosynthesis of glutamine from glutamate and ammonia (PubMed:7937767, PubMed:12819079). Also able to use GTP (PubMed:7937767). D-glutamate is a poor substrate, and DL-glutamate shows about 50% of the standard specific activity (PubMed:7937767). Also plays a key role in controlling the ammonia levels within infected host cells and so contributes to the pathogens capacity to inhibit phagosome acidification and phagosome-lysosome fusion (PubMed:7937767, PubMed:12819079). Involved in cell wall biosynthesis via the production of the major component poly-L-glutamine (PLG) (PubMed:7937767, PubMed:10618433). PLG synthesis in the cell wall occurs only in nitrogen limiting conditions and on the contrary high nitrogen conditions inhibit PLG synthesis (Probable).[1] [2] [3] [4] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedGlutamine synthetase (GS, EC 6.3.1.2; 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-di one, was also shown to inhibit the enzyme, with a measured IC(50) of 2.5+/-0.4 microM. Two X-ray structures are presented: one is a complex of the enzyme with the purine analogue alone (2.55-A resolution), and the other includes the compound together with methionine sulfoximine phosphate, magnesium and phosphate (2.2-A 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 approximately 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. Structural basis for the inhibition of Mycobacterium tuberculosis glutamine synthetase by novel ATP-competitive inhibitors.,Nilsson MT, Krajewski WW, Yellagunda S, Prabhumurthy S, Chamarahally GN, Siddamadappa C, Srinivasa BR, Yahiaoui S, Larhed M, Karlen A, Jones TA, Mowbray SL J Mol Biol. 2009 Oct 23;393(2):504-13. Epub 2009 Aug 18. PMID:19695264[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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