1. Molecular determinants of Burkholderia pseudomallei BpeEF-OprC efflux pump expression.
- Author
-
Rhodes KA, Somprasong N, Podnecky NL, Mima T, Chirakul S, and Schweizer HP
- Subjects
- Anti-Bacterial Agents metabolism, Binding Sites, Biological Transport, Active, DNA, Bacterial, Drug Resistance, Bacterial, Electrophoresis, Polyacrylamide Gel, Electrophoretic Mobility Shift Assay, Gene Deletion, Operon, Protein Binding, Protein Multimerization, Transcription, Genetic, Burkholderia pseudomallei enzymology, Burkholderia pseudomallei genetics, Gene Expression Regulation, Bacterial, Membrane Transport Proteins genetics, Membrane Transport Proteins metabolism
- Abstract
Burkholderia pseudomallei, the cause of melioidosis, is intrinsically resistant to many antibiotics. Acquired multidrug resistance, including resistance to doxycycline and co-trimoxazole used for melioidosis eradication phase therapy, is mainly attributed to constitutive expression of the BpeEF-OprC efflux pump. Constitutive expression of this pump is caused by mutations affecting two highly similar LysR-type transcriptional regulators (LTTR), BpeT and BpeS, but their interaction with the regulatory region governing BpeEF-OprC expression has not yet been studied. The bpeE-bpeF-oprC genes are distally located in the llpE-bpeE-bpeF-oprC operon. The llpE gene encodes a putative lipase/esterase of unknown function. We show that in a bpeT mutant llpE is constitutively co-transcribed with bpeE-bpeF-oprC. As expected from previous studies with B. cenocepacia, deletion of llpE does not affect antibiotic efflux. Using transcriptional bpeE'-lacZ fusions, we demonstrate that the 188 bp bpeT-llpE intergenic region located between bpeT and the llpE-bpeE-bpeF-oprC operon contains regulatory elements needed for control of bpeT and llpE-bpeE-bpeF-oprC operon expression. By native polyacrylamide gel electrophoresis and electrophoretic mobility shift assays with purified recombinant BpeT and BpeS proteins, we show BpeT and BpeS form oligomers that share a 14 bp binding site overlapping the essential region required for llpE-bpeE-bpeF-oprC expression. The binding site contains the conserved T-N11-A LTTR box motif involved in binding of LysR proteins, which in concert with two other possible LTTR boxes may mediate BpeT and BpeS regulation of BpeEF-OprC expression. These studies form the basis for further investigation of BpeEF-OprC expression and regulation at the molecular level by yet unknown external stimuli.
- Published
- 2018
- Full Text
- View/download PDF