Dataset Information

Conformational flexibility of the glycosidase NagZ allows it to bind structurally diverse inhibitors to suppress ?-lactam antibiotic resistance.

ABSTRACT: NagZ is an N-acetyl-?-d-glucosaminidase that participates in the peptidoglycan (PG) recycling pathway of Gram-negative bacteria by removing N-acetyl-glucosamine (GlcNAc) from PG fragments that have been excised from the cell wall during growth. The 1,6-anhydromuramoyl-peptide products generated by NagZ activate ?-lactam resistance in many Gram-negative bacteria by inducing the expression of AmpC ?-lactamase. Blocking NagZ activity can thereby suppress ?-lactam antibiotic resistance in these bacteria. The NagZ active site is dynamic and it accommodates distortion of the glycan substrate during catalysis using a mobile catalytic loop that carries a histidine residue which serves as the active site general acid/base catalyst. Here, we show that flexibility of this catalytic loop also accommodates structural differences in small molecule inhibitors of NagZ, which could be exploited to improve inhibitor specificity. X-ray structures of NagZ bound to the potent yet non-selective N-acetyl-?-glucosaminidase inhibitor PUGNAc (O-(2-acetamido-2-deoxy-d-glucopyranosylidene) amino-N-phenylcarbamate), and two NagZ-selective inhibitors - EtBuPUG, a PUGNAc derivative bearing a 2-N-ethylbutyryl group, and MM-156, a 3-N-butyryl trihydroxyazepane, revealed that the phenylcarbamate moiety of PUGNAc and EtBuPUG completely displaces the catalytic loop from the NagZ active site to yield a catalytically incompetent form of the enzyme. In contrast, the catalytic loop was found positioned in the catalytically active conformation within the NagZ active site when bound to MM-156, which lacks the phenylcarbamate extension. Displacement of the catalytic loop by PUGNAc and its N-acyl derivative EtBuPUG alters the active site conformation of NagZ, which presents an additional strategy to improve the potency and specificity of NagZ inhibitors.

SUBMITTER: Vadlamani G

PROVIDER: S-EPMC5441427 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Conformational flexibility of the glycosidase NagZ allows it to bind structurally diverse inhibitors to suppress β-lactam antibiotic resistance.

Vadlamani Grishma G Stubbs Keith A KA Désiré Jérôme J Blériot Yves Y Vocadlo David J DJ Mark Brian L BL

Protein science : a publication of the Protein Society 20170407 6

NagZ is an N-acetyl-β-d-glucosaminidase that participates in the peptidoglycan (PG) recycling pathway of Gram-negative bacteria by removing N-acetyl-glucosamine (GlcNAc) from PG fragments that have been excised from the cell wall during growth. The 1,6-anhydromuramoyl-peptide products generated by NagZ activate β-lactam resistance in many Gram-negative bacteria by inducing the expression of AmpC β-lactamase. Blocking NagZ activity can thereby suppress β-lactam antibiotic resistance in these bact ...[more]

PMID: 28370529

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Project description:Environmental obesogens are a newly recognized category of endocrine disrupting chemicals that have been implicated in contributing to the rising rates of obesity in the United States. While obesity is typically regarded as an increase in visceral fat, adipocyte accumulation in the bone has been linked to increased fracture risk, lower bone density, and osteoporosis. Exposure to environmental toxicants that activate peroxisome proliferator activated receptor γ (PPARγ), a critical regulator of the balance of differentiation between adipogenesis and osteogenesis, may contribute to the increasing prevalence of osteoporosis. However, induction of adipogenesis and suppression of osteogenesis are separable activities of PPARγ, and ligands may selectively alter these activities. It currently is unknown whether suppression of osteogenesis is a common toxic endpoint of environmental PPARγ ligands. Using a primary mouse bone marrow culture model, we tested the hypothesis that environmental toxicants acting as PPARγ agonists divert the differentiation pathway of bone marrow-derived multipotent mesenchymal stromal cells towards adipogenesis and away from osteogenesis. The toxicants tested included the organotins tributyltin and triphenyltin, a ubiquitous phthalate metabolite (mono-(2-ethylhexyl) phthalate, MEHP), and two brominated flame retardants (tetrabromobisphenol-a, TBBPA, and mono-(2-ethylhexyl) tetrabromophthalate, METBP). All of the compounds activated PPARγ1 and 2. All compounds increased adipogenesis (lipid accumulation, Fabp4 expression) and suppressed osteogenesis (alkaline phosphatase activity, Osx expression) in mouse primary bone marrow cultures, but with different potencies and efficacies. Despite structural dissimilarities, there was a strong negative correlation between efficacies to induce adipogenesis and suppress osteogenesis, with the organotins being distinct in their exceptional ability to suppress osteogenesis. As human exposure to a mixture of toxicants is likely, albeit at low doses, the fact that multiple toxicants are capable of suppressing bone formation supports the hypothesis that environmental PPARγ ligands represent an emerging threat to human bone health.

Dataset Information

Conformational flexibility of the glycosidase NagZ allows it to bind structurally diverse inhibitors to suppress ?-lactam antibiotic resistance.

Publications

Conformational flexibility of the glycosidase NagZ allows it to bind structurally diverse inhibitors to suppress β-lactam antibiotic resistance.

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