title: Isolation and characterization of the nifUSVW-rpoN gene cluster from Rhodobacter sphaeroides.
abstract: The rpoN gene from Rhodobacter sphaeroides was isolated from a genomic library via complementation of a Rhodobacter capsulatus rpoN mutant. The rpoN gene was located on a 7.5-kb HindIII-EcoRI fragment. A Tn5 insertion analysis of this DNA fragment showed that a minimal DNA fragment of 5.3 kb was required for complementation. Nucleotide sequencing of the complementing region revealed the presence of nifUSVW genes upstream from rpoN. The rpoN gene was mutagenized via insertion of a gene encoding kanamycin resistance. The resulting rpoN mutant was not impaired in diazotrophic growth and was in all respects indistinguishable from the wild-type strain. Southern hybridizations using the cloned rpoN gene as a probe indicated the presence of a second rpoN gene. Deletion of the nifUS genes resulted in strongly reduced diazotrophic growth. Two conserved regions were identified in a NifV LeuA amino acid sequence alignment. Similar regions were found in pyruvate carboxylase and oxaloacetate decarboxylase. It is proposed that these conserved regions represent keto acid-binding sites.
authors.affiliation: Department of Microbiology, Ohio State University, Columbus 43210-1292.
authors.forename: W G
authors.initials: WG
authors.lastname: Meijer
authors.forename: F R
authors.initials: FR
authors.lastname: Tabita
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D015139:Blotting, Southern; D003001:Cloning, Molecular; D004251:DNA Transposable Elements / Q000235:genetics; D004268:DNA-Binding Proteins; D012321:DNA-Directed RNA Polymerases; D005798:Genes, Bacterial / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics*; D009154:Mutation / Q000235:genetics; D009586:Nitrogen Fixation / Q000235:genetics; D009876:Operon / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D051877:RNA Polymerase Sigma 54; D012242:Rhodobacter sphaeroides / Q000201:enzymology / Q000235:genetics*; D016415:Sequence Alignment; D012808:Sigma Factor / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; C088637:NifU protein, Bacteria; D012808:Sigma Factor; D012321:DNA-Directed RNA Polymerases; D051877:RNA Polymerase Sigma 54