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- Title
Isolation and characterization of a Pseudomonas aeruginosa gene, ptxR, which positively regulates exotoxin A production.
- Authors
Hamood, Abdul N.; Colmer, Jane A.; Ochsner, Urs A.; Vasil, Michael L.
- Abstract
Exotoxin A production in <em>Pseudomonas aeruginosa</em> is a complicated and highly regulated process that involves several genes. In this report, we describe the isolation of a new <em>toxA</em> regulatory gene (<em>ptxR</em>) which affects exotoxin A production in <em>P. aeruginosa</em>. In an iron-deficient medium, the presence of a plasmid carrying <em>ptxR</em>in <em>P. aeruginosa</em> PAO1 resulted in a four- to fivefold increase in exotoxin A synthesis. No effect was observed on the levels of elastase, phospholipase C, exoenzyme S, and alkaline protease. Using sub-cloning and complementation experiments, <em>ptxR</em> was localized to a 2.1 kb <em>KpnI-BglII</em> fragment. Nucleotide sequence analysis revealed the presence of an open reading frame which encodes a 34.97 kDa protein (PtxR). The size of the predicted PtxR compares closely with the 34 kDa PtxR that was synthesized in <em>Escherichia coli</em> using the T7 expression system. The deduced amino acid sequence of PtxR is homologous to that of several members of the LysR family of transcriptional activators. The amino-terminus region of PtxR contains a putative helix-turn-helix DNA-binding motif. Specific <em>pfxR</em>-deletion mutants in <em>P. aeruginosa</em> strains PAO1 and PA103 were constructed. In comparison with their parent strains, both mutants showed a significant reduction in the level of exotoxin A activity. However, upon extensive subculturing, the level of exotoxin A produced by the PAO1:: <em>ptxR</em> mutant was similar to that of PAO1. Transcriptional studies, using both <em>toxA-lacZ</em> fusion and RNA analysis, confirmed that <em>ptxR</em> increases <em>toxA</em> and <em>regA</em> transcription. These results suggest that <em>ptxR</em> regulates (through <em>regA</em>) exotoxin A production at the transcriptional level.
- Subjects
PSEUDOMONAS aeruginosa; PSEUDOMONAS; GENES; PLASMIDS; NUCLEOTIDE sequence
- Publication
Molecular Microbiology, 1996, Vol 21, Issue 1, p97
- ISSN
0950-382X
- Publication type
Article
- DOI
10.1046/j.1365-2958.1996.6251337.x