Down-regulation of the Escherichia coli K-12 nrf promoter by binding of the NsrR nitric oxide sensing transcription repressor to an upstream site.

FNR-dependent activation of the Escherichia coli K-12 nrf promoter is down-regulated by the nitric oxide-sensitive NsrR protein, together with the nucleoid-associated protein, IHF, which bind to overlapping targets adjacent to the DNA site for FNR. The NsrR target is inactivated by mutation at the Salmonella enterica serovar Typhimurium nrf promoter.