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. Author manuscript; available in PMC: 2018 May 30.
Published in final edited form as: Curr Opin Microbiol. 2017 May 30;36:128–137. doi: 10.1016/j.mib.2017.05.004

Figure 1.

Figure 1

Promoter recognition by ECF sigma factors. (a) Domain 2 from σEEc bound to the nontemplate strand of the −10 promoter element is shown. Protein helices are in red and loops are in gray, while promoter DNA is in blue. The loop that determines binding specificity is indicated. It forms a pocket for the cytosine base, shown in ball and stick format, that is flipped out from the ssDNA helix. (b) Domain 4 from σEEc bound to the −35 promoter element is shown. Protein helices are in green and loops in gray. (c) Schematic of conserved regions of ECF and primary sigma factors are diagrammed. Interactions between individual sigma factor domains and the promoter are indicated by dashed lines. NCR is the nonconserved region of primary sigma factors. Disc. is the discriminator motif and ext. −10 is the extended −10 motif. Structural representations were generated from PDB 4LUP [17] and 2H27 [16] using Chimera [44].