The VanYD DD-carboxypeptidase of Enterococcus faecium BM4339 is a penicillin-binding protein
| Autor: | Barbara Casadewall, O. Herman Ambur, Patrice Courvalin, Peter E. Reynolds |
|---|---|
| Rok vydání: | 2001 |
| Předmět: |
Penicillin binding proteins
Penicillin Resistance Enterococcus faecium Carboxypeptidases Peptidoglycan Muramoylpentapeptide Carboxypeptidase Biology Models Biological Microbiology Benzylpenicillin chemistry.chemical_compound Bacterial Proteins Catalytic Domain polycyclic compounds medicine Penicillin-Binding Proteins Enzyme Inhibitors Binding protein Membrane Proteins Active site Penicillin G Vancomycin Resistance biochemical phenomena metabolism and nutrition biology.organism_classification Uridine Diphosphate N-Acetylmuramic Acid carbohydrates (lipids) Hexosyltransferases chemistry Biochemistry Peptidyl Transferases biology.protein Carboxypeptidase A bacteria Carrier Proteins Protein A Oligopeptides medicine.drug |
| Zdroj: | Microbiology. 147:2571-2578 |
| ISSN: | 1465-2080 1350-0872 |
| DOI: | 10.1099/00221287-147-9-2571 |
| Popis: | VanD-type Enterococcus faecium BM4339 is constitutively resistant to vancomycin and to low levels of teicoplanin. This strain produces peptidoglycan precursors terminating in D-lactate but, unlike VanA- and VanB-type strains, E. faecium BM4339 has a mutated ddl ligase gene and cannot synthesize D-Ala-D-Ala. Consequently, although it possesses vanX(D) and vanY(D) genes, it should not require an active VanX-type DD-dipeptidase or a VanY-type DD-carboxypeptidase for resistance. The vanY(D) gene contains the signatures of a penicillin-binding protein (PBP) and is believed to encode a penicillin-sensitive DD-carboxypeptidase. The enzyme activity was found to be membrane-bound and inhibited by low concentrations of benzylpenicillin in membrane preparations and in intact bacteria, indicating that the active site was present on the outside surface of the membrane. The 38 kDa protein was revealed as a PBP present in more copies per cell than conventional PBPs and all the protein was accessible to benzylpenicillin added externally, confirming the localization of the active site. A glycopeptide-susceptible strain of E. faecium lacked this PBP, and the membrane-bound DD-carboxypeptidase activity was less than 5% of that of E. faecium BM4339. Although the active site of VanY(D) was external to the membrane, UDP-MurNAc-tetrapeptide was produced internally, probably from UDP-MurNAc-pentadepsipeptide. The presence of benzylpenicillin at low concentrations in the growth medium substantially reduced the amount of tetrapeptide produced, indicating that inhibition of VanY(D) by benzylpenicillin influenced production of peptidoglycan precursors internally. A model to explain these contrasting observations is proposed. |
| Databáze: | OpenAIRE |
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