Figure 4.
Mutation of the conserved residues in the tox-box eliminate TOXE binding. (A) Representation of the TOXA/HTS1 promoter. Hatched boxes indicate the two tox-boxes. (B) Double-stranded oligonucleotides containing the wild-type (Wt) tox-box sequence (underlined) and surrounding nucleotides, and a mutant version (Mut) in which all five of the highly conserved nucleotides were changed (indicated in bold lettering), were used as 32P-labeled probes against southwestern blots. “−” Indicates total protein extracts from E. coli not expressing TOXE (control), and “+” indicates E. coli expressing TOXE.