Nucleotide sequence of the fixABC region of Azorhizobium caulinodans ORS571: similarity of the fixB product with eukaryotic flavoproteins, characterization of fixX , and identification of nifW

摘要: The nucleotide sequence of a 4.1 kb DNA fragment containing the fixABC region Azorhizobium caulinodans was established. three gene products were very similar to corresponding polypeptides Rhizobium meliloti. C-terminal domains both fixB displayed high degree similarity with α-subunits rat and human electron transfer flavoproteins, suggesting role for FixB protein in redox reaction. Two open reading frames (ORF) found downstream fixC. first ORF identified as fixX on basis homology from several Bradyrhizobium strains. second potentially encoded 69 amino acid product be homologous Rhodobacter capsulatus nif cluster I. Insertion mutagenesis A. conferred Nif− phenotype bacteria grown free-living state Fix− symbiotic association host plant Sesbania rostrata. A crude extract mutant had no nitrogenase activity. Furthermore, data presented this paper also indicate that previously nifO located upstream fixA probably homologue nifW Klebsiella pneumoniae Azotobacter vinelandii.