Cloning and sequence analysis of the ntrA (rpoN) gene of Pseudomonas putida

The gene encoding a sigma factor NtrA (RpoN) was cloned from Pseudomonas putida by cross-hybridization with a probe containing a part of the corresponding Escherichia coli gene. The cloned gene complemented an ntrA mutation of E. coli in activation of xyl genes on the TOL plasmid. The predicted amino acid (aa) sequence of P. putida NtrA (497 aa; Mr 56,215) is highly homologous to NtrA proteins from Azotobacter vinelandii (81.7%), Klebsiella pneumoniae (52.6%), and Rhizobium meliloti (36.1%). There are two other open reading frames (ORF1, ORF3) upstream and downstream from the ntrA gene, respectively. These ntrA-flanking ORFs are also highly homologous to the corresponding ORFs of K. pneumoniae, A. vinelandii, and R. meliloti.