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Antimicrob. Agents Chemother., 11 1997, 2399-2405, Vol 41, No. 11
S Trepanier, A Prince and A Huletsky
Burkholderia cepacia is recognized as an important pathogen in the lung
infections of patients with cystic fibrosis. An inducible beta- lactamase
activity has been associated with increased resistance to beta-lactam
antibiotics in clinical isolates of B. cepacia. In this study, we report
the revised sequence of the penA gene, which encodes the inducible
penicillinase of B. cepacia, and show that it belongs to the molecular
class A beta-lactamases and exhibits a high degree of similarity to the
chromosomal beta-lactamase of Klebsiella oxytoca. Analysis of the
nucleotide sequence of the DNA region directly upstream of the penA coding
sequence revealed an open reading frame (penR), the transcription of which
was oriented opposite to that of penA and whose initiation was 130 bp away
from that of penA. Two potential ribosome- binding sites and two
overlapping -10 and -35 promoter sequences were identified in the
intercistronic region. The predicted translation product of penR was a
polypeptide of 301 amino acids with an estimated molecular size of 33.2
kDa. The deduced polypeptide of penR showed a high degree of similarity
with AmpR-like transcriptional activators of class A and C beta-lactamases,
with identities of 59 and 58.7% with Pseudomonas aeruginosa PAO1 AmpR and
Proteus vulgaris B317 CumR, respectively. The N-terminal portion of B.
cepacia PenR was predicted to include a helix-turn-helix motif, which may
bind the LysR motif identified in the intercistronic region. Induction of
PenA by imipenem was shown to be dependent upon the presence of PenR.
Expression of the cloned B. cepacia penA and penR genes in Escherichia coli
SNO302 (ampD) resulted in a high basal and hyperinducible PenA activity.
These results suggest that the regulation of the PenA penicillinase of B.
cepacia 249 is similar to that observed in other class A and class C
beta-lactamases that are under the control of a divergently transcribed
AmpR-like regulator.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
Characterization of the penA and penR genes of Burkholderia cepacia 249 which encode the chromosomal class A penicillinase and its LysR-type transcriptional regulator
Departement de Microbiologie, Pavillon Marchand, Universite Laval, Ste- Foy, Quebec, Canada.
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