Nucleotide sequence and characterization of toxR: a gene involved in exotoxin A regulation in Pseudomonas aeruginosa

Abstract

We have previously reported the discovery and subsequent cloning of a regulatory gene, designated toxR, which appears to regulate the expression of the exotoxin A (ETA) structural gene toxA. Subsequent work by this laboratory has resulted in the subcloning of the toxR gene and its transfer to a high copy number plasmid (pGW28). Functional analysis of the toxR gene using a Tn5 insertion along with toxR deletions indicates that inactivation of toxR results in a dramatic reduction of ETA production. Nucleotide sequence analysis of pGW28 has revealed a 675 bp major open reading frame (225 codons) which could encode for a protein of 24,626 daltons. Using S1 nuclease mapping, the toxR RNA transcript has been shown to originate 20 bp upstream of the presumptive translation initiation codon. Experiments using a toxA specific probe have revealed the the toxR gene product appears to regulate the expression of ETA at the transcriptional level.