3t36

Crystal structure of lytic transglycosylase MltE from Eschericha coli

spinqualitylabelsall models 3t36, resolution 2.25Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3t36 is a 5 chain structure with sequence from Escherichia coli k-12. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: SO4 Related: 3t1z, 3t21, 3t4i Gene: emtA, mltE, sltZ, ycgP, b1193, JW5821 (Escherichia coli K-12) Resources: FirstGlance, OCA, RCSB, PDBsum Publication Abstract from PubMed The lytic transglycosylase MltE from Escherichia coli is a periplasmic, outer membrane-attached enzyme that cleaves the beta-1,4-glycosidic bonds between N-acetylmuramic acid and N-acetylglucosamine residues in the cell wall peptidoglycan, producing 1,6-anhydromuropeptides. Here we report three crystal structures of MltE: in a substrate-free state, in a binary complex with chitopentaose, and in a ternary complex with the glycopeptide inhibitor bulgecin A and the murodipeptide N-acetylglucosaminyl-N-acetylmuramyl-l-Ala-d-Glu. The substrate-bound structures allowed a detailed analysis of the saccharide-binding interactions in six subsites of the peptidoglycan-binding groove (subsites -4 to +2) and, combined with site-directed mutagenesis analysis, confirmed the role of Glu64 as catalytic acid/base. The structures permitted the precise modeling of a short glycan strand of eight saccharide residues, providing evidence for two additional subsites (+3 and +4) and revealing the productive conformational state of the substrate at subsites -1 and +1, where the glycosidic bond is cleaved. Full accessibility of the peptidoglycan-binding groove and preferential binding of an N-acetylmuramic acid residue in a (4)C(1) chair conformation at subsite +2 explain why MltE shows only endo- and no exo-specific activity toward glycan strands. The results further indicate that catalysis of glycosidic bond cleavage by MltE proceeds via distortion toward a sofa-like conformation of the N-acetylmuramic acid sugar ring at subsite -1 and by anchimeric assistance of the sugar's N-acetyl group, as shown previously for the lytic transglycosylases Slt70 and MltB. On the Mechanism of Peptidoglycan Binding and Cleavage by the endo-Specific Lytic Transglycosylase MltE from Escherichia coli.,Fibriansah G, Gliubich FI, Thunnissen AM Biochemistry. 2012 Oct 30. PMID:23075328 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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