Figure 1.

Promoter sequence, organization and recognition. (A) The panel shows a DNA sequence logo generated from the alignment of 554 E. coli promoters produced by Mitchell et al. (10). Different promoter elements are labelled. (B) A structural model of the RNA polymerase holoenzyme–DNA complex is shown (12). With the exception of the two α-subunits, each RNA polymerase component protein is shown in a different colour and is labelled. The DNA is shown in green with the base pair at position −18 highlighted in red. The expansion shows the close proximity of the loop between σ⁷⁰ domains 2 and 3 and the promoter non-template strand. Residues in σ⁷⁰ mutated during the course of this work are highlighted and labelled in the expansion.