Transcription of glnA in E. coli is stimulated by activator bound to sites far from the promoter.

Transcription of the Escherichia coli glnALG operon, whose products are glutamine synthetase and the regulatory proteins NRII and NRI, is activated by nitrogen deprivation. Initiation of transcription at the nitrogen-regulated promoter glnAp2 requires sigma 60, the product of rpoN (glnF, ntrA), and NRI, the product of glnG (ntrC). We have now shown that the ability of this promoter to be activated by a low intracellular concentration of NRI depends on two binding sites for NRI located approximately 110 and 140 bp, respectively, upstream of the start of transcription. Moving these binding sites more than 1000 bp does not diminish the ability of NRI to stimulate transcription at glnAp2. Thus, the NRI binding sites resemble enhancers in eukaryotic cells.