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Journal of Bacteriology, June 2001, p. 3436-3446, Vol. 183, No. 11
Unité des Agents Antibactériens,
Institut Pasteur, 75724 Paris Cedex 15, France,1
and Department of Biochemistry, University of Cambridge,
Cambridge, United Kingdom CB2 1QW2
Received 17 November 2000/Accepted 13 March 2001
A new open reading frame, encoding a putative integrase-like
protein, was detected downstream from the six genes of the
vanD glycopeptide resistance cluster in Enterococcus
faecium BM4339 (B. Casadewall and P. Courvalin, J. Bacteriol.
181:3644-3648, 1999). In this cluster, genes coding for the
VanRD-VanSD two-component regulatory system
were cotranscribed from the PRD
promoter, whereas transcription of the vanYD,
vanHD, vanD, vanXD, and intD genes was initiated from the PYD
promoter located between vanSD and
vanYD (the D subscript indicates that the gene
is part of the vanD operon). The
VanRD-VanSD regulatory system is likely to
activate transcription of the resistance genes from the promoter PYD. Glycopeptide-susceptible
derivatives of BM4339 were obtained by trans
complementation of the frameshift mutation in the ddl gene,
restoring functional D-alanine:D-alanine ligase activity in this strain. The glycopeptide-susceptible transformant BM4409, producing only
D-alanyl-D-alanine-terminating peptidoglycan precursors, did not express the resistance genes encoding the VanYD D,D-carboxypeptidase, the
VanHD dehydrogenase, the VanD ligase, the VanXD
D,D-dipeptidase, and also the IntD integrase, although the regulatory region of the vanD cluster was
still transcribed. In BM4409, the absence of
VanRD-VanSD, apparently dependent,
transcription from promoter PYD
correlated with the lack of
D-alanyl-D-lactate-terminating precursors. The
vanXD gene was transcribed in BM4339, but
detectable amounts of VanXD
D,D-dipeptidase were not synthesized. However, the gene directed synthesis of an active enzyme when cloned on a
multicopy plasmid in Escherichia coli, suggesting that the
enzyme was unstable in BM4339 or that it had very low activity that was detectable only under conditions of high gene dosage. This activity is
not required for glycopeptide resistance in BM4339, since this strain
cannot synthesize D-alanyl-D-alanine.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.11.3436-3446.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Regulation of Expression of the vanD
Glycopeptide Resistance Gene Cluster from Enterococcus
faecium BM4339
*
Corresponding author. Mailing address: Unité des
Agents Antibactériens, Institut Pasteur, 28 rue du Docteur Roux,
75724 Paris Cedex 15, France. Phone: 33 1 45 68 83 20. Fax: 33 1 45 68 83 19. E-mail: pcourval{at}pasteur.fr.
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