1ct9
CRYSTAL STRUCTURE OF ASPARAGINE SYNTHETASE B FROM ESCHERICHIA COLI
Structural highlights
FunctionASNB_ECOLI Catalyzes the ATP-dependent conversion of aspartate into asparagine, using glutamine as a source of nitrogen. Can also use ammonia as the nitrogen source in vitro, albeit with lower efficiency. As nucleotide substrates, ATP and dATP are utilized at a similar rate in both the glutamine- and ammonia-dependent reactions, whereas GTP utilization is only 15% that of ATP, and CTP, UTP, ITP and XTP are very poor or not substrates. Also exhibits glutaminase activity.[1] [2] [3] 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 PubMedAsparagine synthetase B catalyzes the assembly of asparagine from aspartate, Mg(2+)ATP, and glutamine. Here, we describe the three-dimensional structure of the enzyme from Escherichia colidetermined and refined to 2.0 A resolution. Protein employed for this study was that of a site-directed mutant protein, Cys1Ala. Large crystals were grown in the presence of both glutamine and AMP. Each subunit of the dimeric protein folds into two distinct domains. The N-terminal region contains two layers of antiparallel beta-sheet with each layer containing six strands. Wedged between these layers of sheet is the active site responsible for the hydrolysis of glutamine. Key side chains employed for positioning the glutamine substrate within the binding pocket include Arg 49, Asn 74, Glu 76, and Asp 98. The C-terminal domain, responsible for the binding of both Mg(2+)ATP and aspartate, is dominated by a five-stranded parallel beta-sheet flanked on either side by alpha-helices. The AMP moiety is anchored to the protein via hydrogen bonds with O(gamma) of Ser 346 and the backbone carbonyl and amide groups of Val 272, Leu 232, and Gly 347. As observed for other amidotransferases, the two active sites are connected by a tunnel lined primarily with backbone atoms and hydrophobic and nonpolar amino acid residues. Strikingly, the three-dimensional architecture of the N-terminal domain of asparagine synthetase B is similar to that observed for glutamine phosphoribosylpyrophosphate amidotransferase while the molecular motif of the C-domain is reminiscent to that observed for GMP synthetase. Three-dimensional structure of Escherichia coli asparagine synthetase B: a short journey from substrate to product.,Larsen TM, Boehlein SK, Schuster SM, Richards NG, Thoden JB, Holden HM, Rayment I Biochemistry. 1999 Dec 7;38(49):16146-57. PMID:10587437[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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