Fig 9.

Transcription activation at the glnAp2 promoter. (A) Two NRI-P dimers bind the enhancer, which is composed of two binding sites for dimers. The enhancer is located at positions −108 and −140 with respect to the transcription start site. The RNA polymerase holoenzyme containing sigma factor 54 (Eσ⁵⁴) binds to the glnAp2 promoter to form a closed complex. (B) Two NRI-P dimers contact the Eσ⁵⁴ holoenzyme by means of DNA loop formation (intermediate complex). (C) Hydrolysis of ATP by NRI-P results in the formation of an open complex, i.e., DNA strand separation at the promoter. (Adapted from reference 181.)