VanS is a transmembrane protein that
autophosphorylates when it detects an incoming glycopeptide,
which then phosphylates VanR that acts on the
essential promoter of the operon. The vanA operon is
effective against all glycopeptides that can initiate induction
including teicoplanin. There are several similar
operons in VRE; the second in importance is the vanB
operon in Tn1547, which confers lower resistance to
vancomycin and none to teicoplanin because this glycopeptide
does not act as an inducer [5]. The vanC and vanE
operons employ serine instead of lactate as the glycopeptide-insusceptible
terminal moiety in the pentapeptide in
peptidoglycan synthesis [4,6].
Variations in the vanA operon that are dependent on the
area that the host pathogen has been isolated have been
identified; for instance, the nucleotide sequence of operons
from strains isolated in the United States differs from
those in the UK [7]. However, this operon can also vary
within a small geographical area and different insertions