Fig. 3.

Alignment of σ factors from E. coli, P. aeruginosa and A. baumannii. Multiple alignments were performed for σ factors found in A. baumannii AB5075, E. coli and P. aeruginosa. (a) Conservation in regions 2.4 and 4.2, which are essential for promoter recognition, as well as region 3 (all indicated by blue boxes), were observed. (b) Two conserved amino acid sequences critical for binding to DnaK (blue boxes) were noted for all three RpoH proteins. (c) Several leucine residues, within a conserved heptad motif, and a conserved amino acid sequence only found in σ54 family proteins (blue box), were identified in RpoN homologues. (d) Blue boxes indicate a conserved amino acid sequence within regions 2 and 4 of RpoE, important for transcription of rpoE and promoter recognition in general. (e) Asterisks indicate conservation of a leucine residue essential for FecI–FecR interaction, and a lysine residue critical for binding to the β subunit of RNAP. Throughout this figure, pink boxes represent amino acids that display divergence between the compared sequences.