Disease relevance of vanX

• Expression of vanX in E. faecalis and Escherichia coli resulted in production of a D,D-dipeptidase that hydrolysed D-Ala-D-Ala [1].
• The vanR, vanS, vanH, vanA, and vanX genes of enterococcal transposon Tn1546 were introduced into the chromosome of Enterococcus faecalis JH2-2 [2].

High impact information on vanX

• The enzyme could not replace the VanX D,D-dipeptidase for the expression of glycopeptide resistance but a G237D substitution in the host D-Ala:D-Ala ligase restored resistance in a vanX null mutant [3].
• The vanX gene was located downstream from genes encoding the VanA ligase and the VanH dehydrogenase which synthesize the depsipeptide D-alanyl-D-lactate (D-Ala-D-Lac) [1].
• All vancomycin-resistant isolates examined carried the vanA, vanX, and vanR genes, suggesting that a gene cluster similar to that of the transposon Tn1546 was responsible for the resistance [4].
• Multicopy plasmids pAT80 (vanR vanS vanH vanA vanX) and pAT382 (vanR vanS vanH vanA vanX vanY) conferred similar levels of vancomycin resistance to JH2-2 [2].
• Transcription of cat and vanX was inducible by glycopeptides in partial diploids harboring vanS and vanS(omega)cat but was constitutive in strains containing only vanS(omega)cat [5].

Other interactions of vanX

• Our results show that the vancomycin resistance determinant in L. rhamnosus GG is not closely related to enterococcal van genes, since no PCR product was amplified in L. rhamnosus GG with any of the three sets of vanA primers used, and enterococcal vanA, vanB, vnH, vanX, vanZ, vanY, vanS and vanR genes did not hybridize with DNA of L. rhamnosus GG [6].

References