Fig. 1

The intercistronic bidirectional promoter region between E. coli fepB and entC. a The sequence contains all nucleotides between the fepB and entC start codons (624511–624884 in E. coli K12 MG1655 (NCBI Reference Number: NC_000913.3). Positions of anti-clockwise regulatory elements (Fur box1, +1 − 10 and −35 sequences for fepB transcriptional regulation) are indicated by dashed lines. Positions of clockwise regulatory elements (Fur box 2, +1 − 10 and −35 sequence for entCEBAH transcriptional regulation) are shown as solid lines. Fur box 1 and Fur box 2 were identified previously [18, 19]. b Sequence alignment of the Fur box consensus sequence with Fur box 1 and Fur box 2. Positions diverging from the consensus sequence are highlighted