1ct9
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CRYSTAL STRUCTURE OF ASPARAGINE SYNTHETASE B FROM ESCHERICHIA COLI
OverviewOverview
Asparagine 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.
About this StructureAbout this Structure
1CT9 is a Single protein structure of sequence from Escherichia coli with IUM, CL, AMP and GLN as ligands. Active as Asparagine synthase (glutamine-hydrolyzing), with EC number 6.3.5.4 Full crystallographic information is available from OCA.
ReferenceReference
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
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