1h74

CRYSTAL STRUCTURE OF HOMOSERINE KINASE COMPLEXED WITH ILE

spinqualitylabelsall models 1h74, resolution 1.90Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1h74 is a 4 chain structure with sequence from Methanocaldococcus jannaschii. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: ADP, AGS, ILE, MG Related: 1fwk, 1fwl, 1h72, 1h73 Activity: Homoserine kinase, with EC number 2.7.1.39 Resources: FirstGlance, OCA, RCSB, PDBsum 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 PubMed Homoserine kinase (HSK), the fourth enzyme in the aspartate pathway of amino acid biosynthesis, catalyzes the phosphorylation of L-homoserine (Hse) to L-homoserine phosphate, an intermediate in the production of L-threonine, L-isoleucine, and in higher plants, L-methionine. The high-resolution structures of Methanococcus jannaschii HSK ternary complexes with its amino acid substrate and ATP analogues have been determined by X-ray crystallography. These structures reveal the structural determinants of the tight and highly specific binding of Hse, which is coupled with local conformational changes that enforce the sequestration of the substrate. The delta-hydroxyl group of bound Hse is only 3.4 A away from the gamma-phosphate of the bound nucleotide, poised for the in-line attack at the gamma-phosphorus. The bound nucleotides are flexible at the triphosphate tail. Nevertheless, a Mg(2+) was located in one of the complexes that binds between the beta- and gamma-phosphates of the nucleotide with good ligand geometry and is coordinated by the side chain of Glu130. No strong nucleophile (base) can be located near the phosphoryl acceptor hydroxyl group. Therefore, we propose that the catalytic mechanism of HSK does not involve a catalytic base for activating the phosphoryl acceptor hydroxyl but instead is mediated via a transition state stabilization mechanism. Structural basis for the catalysis and substrate specificity of homoserine kinase.,Krishna SS, Zhou T, Daugherty M, Osterman A, Zhang H Biochemistry. 2001 Sep 11;40(36):10810-8. PMID:11535056 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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