Fig. 6.

A fhuA promoter and its repression mechanism by HypT. (A) The structure of the fhuA promoter. The fhuA promoter from Salmonella was analyzed by comparing with the E. coli fhuA promoter. The −10 and −35 boxes, recognized by σ⁷⁰, are highlighted by gray boxes. The StHypT binding sequences (red letters on yellow boxes) were determined by DNase I footprinting assay (SI Appendix, Fig. S13). The pseudopalindromic sites are indicated with underlines and red arrows. The transcription start site and translation initiation codon are shown in blue and green letters, respectively. Fur box is indicated by a magenta box. (B) A proposed repression mechanism of StHypT. Red lines, yellow boxes, and gray boxes represent DNA, the StHypT binding site, and the σ factor binding site (−35 and −10 box), respectively. The combination of purple and green illustrations presents the RNA polymerase complex (RNAP), and among them, the green shapes represent σ⁷⁰.