Nucleotide sequence and characterization oftoxR: a gene involved in exotoxin A regulation inPseudomonas aeruginosa

Abstract
We have previously reported (1) 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 1n 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 1nact1vat1on of toxR results In a dramatic reduction of ETA production. Nucleotlde sequence analysis of pGU28 has revealed a 675 bp major open reading frame (225 codons) which could encode for a protein of 24,626 daltons. Using SI nuclease napping, 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