title: Molecular cloning and functional characterisation of VanX, a D-alanyl-D-alanine dipeptidase from Streptomyces coelicolor A3(2).
abstract: The vanX gene which encodes a D-alanyl-D-alanine dipeptidase is critical for vancomycin resistance in enterococci. A putative vanX gene from Streptomyces coelicolor A3(2), which is not known for vancomycin production, was identified by homology-based analysis and cloned by polymerase chain reaction. The S. coelicolor vanX gene was heterologously expressed in Escherichia coli BL21(DE3) and enzymatic assays of soluble protein fractions of VanX revealed a 93-fold increase in dipeptidase activity as compared to the nonrecombinant control, thus confirming its functionality. Interestingly, S. coelicolor was also found to be of intermediate resistance to vancomycin although it does not produce vancomycin, thus suggesting the role of VanX in defence or immunity. As such, the prevalence of vanX genes in the environment may be more common than previously thought.
authors.affiliation: Department of Microbiology, Faculty of Medicine, National University of Singapore, Singapore.
authors.forename: Ai Lin
authors.initials: AL
authors.lastname: Tan
authors.forename: Paxton
authors.initials: P
authors.lastname: Loke
authors.forename: Tiow-Suan
authors.initials: TS
authors.lastname: Sim
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D004150:Dipeptidases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase; D013302:Streptomyces / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D014640:Vancomycin / Q000494:pharmacology; D020713:Vancomycin Resistance / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D014640:Vancomycin; D004150:Dipeptidases; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase; C091956:VanX dipeptidase