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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 
 
 

Mechanisms and implications of glycopeptide resistance in enterococci.

Glycopeptide resistance is recent in enterococci and its expression is inducible by glycopeptides. Two phenotypes can be distinguished: (a) resistance to high levels of vancomycin and teicoplanin, and (b) resistance to low levels of vancomycin only. There is no cross-resistance between glycopeptides, glycolipodepsipeptides (ramoplanin), and lipopeptides (daptomycin). The determinants conferring low-level resistance are nontransferable and presumably chromosomal. High-level resistance is plasmid-mediated and the plasmids range from 34 to 40 kb, are self-transferable, and encode various resistance combinations. All plasmids share the same glycopeptide resistance determinant, which is distinct from that conferring low-level resistance. Induction of resistance is associated with induction of about a 40 kDa protein. We have determined the sequence of the vanA gene encoding one such resistance protein designated VANA. Amino acid sequence similarity was detected between VANA and D-Ala: D-Ala ligases from Enterobacteriaceae. Complementation analysis in Escherichia coli indicated that VANA possesses D-Ala: D-Ala ligase activity and is therefore related to enzymes that catalyze synthesis of glycopeptide target, i.e., terminal D-Ala-D-Ala of peptidoglycan precursors. The contribution of VANA to synthesis of peptidoglycan in the presence of glycopeptides is unknown: VANA could bind to D-Ala-D-Ala, preventing the binding of the drugs; could modify the target of the drug; and could be a ligase with novel specificity.[1]

References

  1. Mechanisms and implications of glycopeptide resistance in enterococci. Derlot, E., Courvalin, P. Am. J. Med. (1991) [Pubmed]
 
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