Baptista M, Depardieu F, Reynolds P, Courvalin P, Arthur M
Unité des Agents Antibactériens, Centre National de la Recherche Scientifique EP J0058, Institut Pasteur, Paris, France.
Mol Microbiol. 1997 Jul;25(1):93-105. doi: 10.1046/j.1365-2958.1997.4401812.x.
The vanB gene cluster mediates glycopeptide resistance by production of peptidoglycan precursors ending in the depsipeptide D-alanyl-D-lactate (D-Ala-D-Lac) instead of D-Ala-D-Ala found in susceptible enterococci. Synthesis of D-Ala-D-Lac and hydrolysis of D-Ala-D-Ala is controlled by the VanR(B)S(B) two-component regulatory system that activates transcription of the resistance genes in response to vancomycin but not to teicoplanin. Two substitutions (A3C-->G or D168-->Y) in the VanS(B) sensor kinase resulted in induction by teicoplanin, indicating that the N-terminal domain of the protein was involved in glycopeptide sensing. A substitution (T237-->K) located in the vicinity of the putative autophosphorylation site of VanS(B) (H233) was associated with a constitutive phenotype and affected a conserved residue known to be critical for the phosphatase activity of related kinases. A mutant producing an impaired host D-Ala:D-Ala ligase required vancomycin for growth, since D-Ala-D-Lac was only produced under inducing conditions. The ddl and vanS(B) mutations, alone or in combination, resulted in various resistance phenotypes that were determined by the amount of D-Ala-D-Ala and D-Ala-D-Lac incorporated into peptidoglycan precursors under different inducing conditions.
vanB基因簇通过产生以二肽D-丙氨酰-D-乳酸（D-Ala-D-Lac）结尾的肽聚糖前体来介导糖肽抗性，而不是易感肠球菌中发现的D-Ala-D-Ala。D-Ala-D-Lac的合成和D-Ala-D-Ala的水解由VanR(B)S(B)双组分调节系统控制，该系统响应万古霉素而不是替考拉宁激活抗性基因的转录。VanS(B)传感激酶中的两个取代（A3C→G或D168→Y）导致替考拉宁诱导，表明该蛋白的N端结构域参与糖肽传感。位于VanS(B)（H233）假定自磷酸化位点附近的一个取代（T237→K）与组成型表型相关，并影响一个已知对相关激酶磷酸酶活性至关重要的保守残基。产生受损宿主D-Ala:D-Ala连接酶的突变体生长需要万古霉素，因为D-Ala-D-Lac仅在诱导条件下产生。ddl和vanS(B)突变单独或组合导致各种抗性表型，这些表型由在不同诱导条件下掺入肽聚糖前体中的D-Ala-D-Ala和D-Ala-D-Lac的量决定。
