Nucleotide sequence of the narL gene that is involved in global regulation of nitrate controlled respiratory genes of Escherichia coli.

The DNA sequence was determined for the narL gene of Escherichia coli. This gene is involved in global regulation of a number of nitrate controlled genes including frdABCD, tor, narGHJI, and adhE which are associated with bacterial respiration and fermentation. Comparison of the deduced amino acid sequence of narL to that of other bacterial genes revealed significant homologies to the phoB, ompR, and virG gene products based on the presence of similar protein domains. These DNA binding proteins are members of two-component regulatory systems. The similarities suggest that narL may also participate in such a two-component regulatory system and that the narR gene, which lies upstream of narL, may encode a second component required for nitrate control of gene regulation. In vitro protein synthesis experiments using a narL plasmid identified a putative NarL protein of 29 kDa in size consistent with the DNA sequence analysis. Primer extension experiments revealed the presence of two 5' termini for narL mRNA, and indicates that transcription may be complex.