The nirB promoter of Escherichia coli: location of nucleotide sequences essential for regulation by oxygen, the FNR protein and nitrite.

Using recombinant DNA techniques, nested deletions have been made upstream of the Escherichia coli nirB transcription start site and their effects on the regulation of nirB promoter activity have been measured. Nucleotide sequences downstream of -73 are sufficient for FNR-dependent induction of activity by anaerobic growth conditions. However, nucleotide sequences between -87 and -149 are essential for further induction by nitrite in the growth medium. The nucleotide sequence at the galP1 CRP binding site located from -31 to -52 displays some similarities with the same region at the nirB promoter. When the galP1 sequence from -30 to -54 was replaced by the corresponding nirB sequence, expression from galP1 became inducible by FNR under anaerobic growth conditions.