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High-resolution crystal structure of MltE, an outer membrane-anchored endolytic peptidoglycan lytic transglycosylase from Escherichia coli.

ABSTRACT: The crystal structure of the first endolytic peptidoglycan lytic transglycosylase MltE from Escherichia coli is reported here. The degradative activity of this enzyme initiates the process of cell wall recycling, which is an integral event in the existence of bacteria. The structure sheds light on how MltE recognizes its substrate, the cell wall peptidoglycan. It also explains the ability of this endolytic enzyme to cleave in the middle of the peptidoglycan chains. Furthermore, the structure reveals how the enzyme is sequestered on the inner leaflet of the outer membrane.

SUBMITTER: Artola-Recolons C

PROVIDER: S-EPMC3068208 | biostudies-literature | 2011 Apr

REPOSITORIES: biostudies-literature

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High-resolution crystal structure of MltE, an outer membrane-anchored endolytic peptidoglycan lytic transglycosylase from Escherichia coli.

Artola-Recolons Cecilia C Carrasco-López César C Llarrull Leticia I LI Kumarasiri Malika M Lastochkin Elena E Martínez de Ilarduya Iñaki I Meindl Kathrin K Usón Isabel I Mobashery Shahriar S Hermoso Juan A JA

Biochemistry 20110308 13

The crystal structure of the first endolytic peptidoglycan lytic transglycosylase MltE from Escherichia coli is reported here. The degradative activity of this enzyme initiates the process of cell wall recycling, which is an integral event in the existence of bacteria. The structure sheds light on how MltE recognizes its substrate, the cell wall peptidoglycan. It also explains the ability of this endolytic enzyme to cleave in the middle of the peptidoglycan chains. Furthermore, the structure rev ...[more]

PMID: 21341761

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Exolytic and endolytic turnover of peptidoglycan by lytic transglycosylase Slt of <i>Pseudomonas aeruginosa</i>.

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Lytic transglycosylase MltB of Escherichia coli and its role in recycling of peptidoglycan strands of bacterial cell wall.

Project description:The cell wall is an indispensable structure for the survival of bacteria and a target for antibiotics. Peptidoglycan is the major constituent of the cell wall, which is comprised of backbone repeats of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM). A peptide stem is appended to the NAM unit, which in turn experiences cross-linking with a peptide from another peptidoglycan in the final steps of cell wall assembly. In the normal course of bacterial growth, as much as 60% of the parental cell wall is recycled, a process that is not fully understood. A polymeric cell wall is fragmented by the family of lytic transglycosylases, and certain key fragments are transported to the cytoplasm for recycling. The genes for the six known lytic transglycosylases of Escherichia coli were cloned, and the enzymes were purified in this study. It is shown that MltB is the only lytic transglycosylase to turn over a synthetic peptidoglycan fragment of two NAG-NAM repeats; hence this enzyme is likely to be the lytic transglycosylase responsible for processing of shorter peptidoglycan strands. Lytic transglycosylases have been proposed to go through an oxocarbenium species that would trap the 6-hydroxyl moiety of the glucosamine residue of muramic acid to generate the so-called 1,6-anhydromuramyl moiety. It is documented herein by characterization of the products of turnover that this process takes place to the total exclusion of the entrapment of a water molecule by the reactive intermediary oxocarbenium species. Furthermore, turnover of the E. coli sacculus (whole cell wall) by MltB was characterized. It is documented that each MltB molecule is able to process the cell wall 14000 times in the course of a single doubling time for E. coli.

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Murein-metabolizing enzymes from Escherichia coli: existence of a second lytic transglycosylase.

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The C-terminal domain of Escherichia coli YfhD functions as a lytic transglycosylase.

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Screen for inhibitors of the coupled transglycosylase-transpeptidase of peptidoglycan biosynthesis in Escherichia coli.

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| S-EPMC1426922 | biostudies-literature

Lytic transglycosylase MltG cleaves in nascent peptidoglycan and produces short glycan strands.

Project description:Bacteria encase their cytoplasmic membrane with peptidoglycan (PG) to maintain the shape of the cell and protect it from bursting. The enlargement of the PG layer is facilitated by the coordinated activities of PG synthesising and -cleaving enzymes. In Escherichia coli, the cytoplasmic membrane-bound lytic transglycosylase MltG associates with PG synthases and was suggested to terminate the polymerisation of PG glycan strands. Using pull-down and surface plasmon resonance, we detected interactions between MltG from Bacillus subtilis and two PG synthases; the class A PBP1 and the class B PBP2B. Using in vitro PG synthesis assays with radio-labelled or fluorophore-labelled B. subtilis-type and/or E. coli-type lipid II, we showed that both, BsMltG and EcMltG, are lytic tranglycosylases and that their activity is higher during ongoing glycan strand polymerisation. MltG competed with the transpeptidase activity of class A PBPs, but had no effect on their glycosyltransferase activity, and produced glycan strands with a length of 7 disaccharide units from cleavage in the nascent strands. We hypothesize that MltG cleaves the nascent strands to produce short glycan strands that are used in the cell for a yet unknown process.

| S-EPMC8135044 | biostudies-literature

Crystal structure of the membrane-bound bifunctional transglycosylase PBP1b from Escherichia coli.

Project description:Drug-resistant bacteria have caused serious medical problems in recent years, and the need for new antibacterial agents is undisputed. Transglycosylase, a multidomain membrane protein essential for cell wall synthesis, is an excellent target for the development of new antibiotics. Here, we determined the X-ray crystal structure of the bifunctional transglycosylase penicillin-binding protein 1b (PBP1b) from Escherichia coli in complex with its inhibitor moenomycin to 2.16-A resolution. In addition to the transglycosylase and transpeptidase domains, our structure provides a complete visualization of this important antibacterial target, and reveals a domain for protein-protein interaction and a transmembrane helix domain essential for substrate binding, enzymatic activity, and membrane orientation.

| S-EPMC2689995 | biostudies-literature

Crystallization and preliminary X-ray diffraction analysis of the lytic transglycosylase MltE from Escherichia coli.

Project description:MltE from Escherichia coli (193 amino acids, 21,380 Da) is a lytic transglycosylase that initiates the first step of cell-wall recycling. This enzyme is responsible for the cleavage of the cell-wall peptidoglycan at the β-1,4-glycosidic bond between the N-acetylglucosamine and N-acetylmuramic acid units. At the end this reaction generates a disaccharide that is internalized and initiates the recycling process. To obtain insights into the biological functions of MltE, crystallization trials were performed and crystals of MltE protein that were suitable for X-ray diffraction analysis were obtained. The MltE protein of E. coli was crystallized using the hanging-drop vapour-diffusion method at 291 K. Crystals grew from a mixture consisting of 28% polyethylene glycol 4000, 0.1 M Tris pH 8.4 and 0.2 M magnesium chloride. Further optimization was performed using the microbatch technique. Single crystals were obtained that belonged to the orthorhombic space group C222(1), with unit-cell parameters a=123.32, b=183.93, c=35.29 Å, and diffracted to a resolution of 2.1 Å.

| S-EPMC3080000 | biostudies-literature

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