4HJZ

1.9 A Crystal structure of E. coli MltE-E64Q with bound chitopentaose

Replaces:  3T21

Summary for 4HJZ

• Entry DOI: 10.2210/pdb4hjz/pdb
• Related: 3T36 4HJV 4HJY
• Descriptor: Endo-type membrane-bound lytic murein transglycosylase A, 2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose, 2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose, ... (5 entities in total)
• Functional Keywords: goose type lysozyme-like structure, lytic transglycosylase, lyase
• Biological source: Escherichia coli
• Cellular location: Cell outer membrane; Lipid-anchor (Probable): P0C960
• Total number of polymer chains: 2
• Total formula weight: 47549.19

Authors

Fibriansah, G.,Gliubich, F.I.,Thunnissen, A.-M.W.H. (deposition date: 2012-10-14, release date: 2012-10-24, Last modification date: 2023-09-20)

Primary citation

Fibriansah, G.,Gliubich, F.I.,Thunnissen, A.M.
On the Mechanism of Peptidoglycan Binding and Cleavage by the endo-Specific Lytic Transglycosylase MltE from Escherichia coli.
Biochemistry, 51:9164-9177, 2012

PubMed Abstract: The lytic transglycosylase MltE from Escherichia coli is a periplasmic, outer membrane-attached enzyme that cleaves the β-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.

PubMed: 23075328
DOI: 10.1021/bi300900t

Experimental method

X-RAY DIFFRACTION (1.9 Å)