IDENTIFICATION OF A SHIGELLA-FLEXNERI CRIR GENE - INCREASING IPA GENES EXPRESSION - A NOVEL MEMBER OF RESPONSE REGULATORS OF THE 2-COMPONENT SIGNAL-TRANSDUCTION FAMILY

A genetic locus named cri, which enhanced the expression of ipa genes, was cloned into Escherichia coli K-12 from Shigella flexneri Ib chrom osomal DNA. Subcloning and Tn5-Tc1 transposon experiments showed that cri locus was located on a 2.6-kb HindIII fragment. Nucleotide sequenc e analysis of the region revealed at least three open reading frames ( ORF), one of which, named criR, encoded a protein of 226 amino-acid re sidues and transcriptionally increased the ipaB expression. The deduce d regulatory protein CriR shared a significant homology with bacterial transcriptional activators of the two-component signal transduction f amily. A homologue of the criR gene was present in genomic DNA of Shig ella spp. and E. coli strains, and mapped at the 14.6-min region of E. coli K-12 chromosomal DNA. These results indicate that criR is a new member of response regulators.