Open AccessMolecular analysis of an essential gene upstream of rpoN in Rhizobium NGR234
Author(s) -
Slooten JanChristoph,
Stanley John
Publication year - 1991
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1991.tb04864.x
Subject(s) - rpon , biology , open reading frame , genetics , operon , gene , transposable element , start codon , plasmid , rhizobium , mutant , promoter , peptide sequence , gene expression , nucleotide
Abstract:Rhizobium sp. NGR234 is a broad‐host range strain. The rpoN gene of this organism encodes a sigma factor which is a primary co‐regulator of endosymbiosis [1]. We characterized the locus upstream of rpoN , and identified a contiguous open reading frame, here termed ORF1. DNA sequence analysis of this ORF showed that it encoded a polypeptide highly conserved with a corresponding ORF of Rhizobium meliloti . The gene product contained two ATP/GTP binding pockets. Codon usage in the ORF and the nitrogenase operon nifKDH of NGR234 was similar. Although we used a non‐transposable cassette flanked by appropriate sized DNA fragments, we were unable to isolate site‐directed mutants in the ORF, whose ATP/GTP binding protein product is thus probably of essential biological function. ORF1 and rpoN exhibited conserved linkage among diverse rhizobia, and in Azotobacter vinelandii . Intragenomic and interspecific homology studies confirmed directly that ORF1 (NGR234) belonged to a large family of ATP‐binding protein genes.