Protein–Protein Contacts that Activate and Repress Prokaryotic Transcription  Ann Hochschild, Simon L Dove  Cell  Volume 92, Issue 5, Pages 597-600 (March 1998) DOI: 10.1016/S0092-8674(00)81126-5

Figure 1 Transcriptional Activation in E. coli (A) A typical σ70-dependent promoter is shown consisting of a −10 and a −35 hexamer, both of which are directly contacted by σ in the holoenzyme (subunit composition α2ββ′σ70). (Note that the preassembled holoenzyme is the DNA-binding species and the α,β,β', and σ subunits are all that are required for efficient and accurate transcription.) In addition, certain particularly strong promoters comprise a third motif known as the UP element, which is located immediately upstream of the −35 region and is bound by the α-CTD (Ross et al. 1993). (B–F) Transcriptional activation by DNA-bound regulators (see text for details). Cell 1998 92, 597-600DOI: (10.1016/S0092-8674(00)81126-5)