FIG 1.

ltrR transcriptional start sites. (A) Schematic diagram of the regulatory region of the ltrR gene. The bent arrows and bold letters represent the transcriptional starts sites; −10 and −35 boxes are shown as white rectangles, and the corresponding sequences are underlined; the nucleotide substitutions in the −10 box are indicated by asterisks; and ATG is the ltrR canonical translational initiation codon. (B) Primer extension of the ltrR regulatory region performed with total RNA of S. Typhi plus pKK8/ltrR-144+90. Two transcriptional initiation sites located upstream at nucleotide −40 and downstream at nucleotide +64, with respect to the initial canonical ATG codon, were identified, and the promoter regions were designated ltrRP2 and ltrRP1, respectively. (C) Primer extension using S. Typhi plus pKK8/ltrR-144+90ΔP2 containing a substitution of the ltrRP2 −10 box. (D) Primer extension using S. Typhi plus pKK8/ltrR-144+90ΔP1 containing a substitution of the ltrRP1 −10 box. Black triangles indicate the transcriptional start sites.