FIG. 5.

EctR1-His₆ binding site at the ectAp₁ promoter region of the ectABC-ask operon. (A) The DNA probes, labeled at the 5′ end of either the top strand or the bottom strand, were incubated with purified EctR1-His₆ and treated with DNase I. The samples were run on a 6% polyacrylamide sequencing gel with a Maxam-Gilbert (A+G) sequencing reaction. (B) Nucleotide sequences of the ectAp₁ promoter region of the ectABC-ask operon. Regions protected by EctR1, as determined by the DNase I protection assay, are indicated by lines. Arrows represent the inverted-repeat sequences found in the EctR1 binding site. The transcription start site from the ectAp₁ promoter is shaded. Putative −10 and −35 sequences for the promoter are shown on a black background.