Nucleotide sequence of the regulatory nifA gene of Rhizobium leguminosarum PRE: transcriptional control sites and expression in Escherichia coli.

We report the sequence of the regulatory nifA gene of Rhizobium leguminosarum PRE. The transcription initiation and termination sites of nifA were mapped and a potential promoter and a rho-independent terminator identified. The nifA gene has two possible translation start sites, both of which are used in an Escherichia coli background, resulting in proteins with apparent molecular weights of 58kD and 57kD; initiation at the second site is preferred over initiation at the first. The nifA-nifB intergenic region contains an rpoN-dependent promoter for the nifB gene but no consensus upstream activator sequence (UAS).