title: Oxygen sensitivity of NifA protein of Azospirillum lipoferum FS as suggested by gene cloning and expression in Escherichia coli.
abstract: We cloned and sequenced a 2.8-kb SalI fragment of Azospirillum lipoferum FS as a homologue of the Klebsiella oxytoca nifA gene. The amino acid sequence deduced from an open reading frame of 1872 bases showed 91% identity to that of the A. brasilense NifA, and the putative central sigma54 interaction domain was conserved as well as the C-terminal DNA-binding domain. The NifA function on the nifH promoter was examined in Escherichia coli using a combination of a nifA driver plasmid and a nifH-lacZ reporter plasmid, in which the transcriptional activation of the nifH promoter by the NifA was evaluated with the beta-galactosidase activity. The A. lipoferum NifA activated the nifH promoter solely under microaerobic conditions, while the K. oxytoca NifA activated it irrespective of the oxygen condition. These observations suggest that oxygen sensitivity is an intrinsic property of the A. lipoferum NifA.
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, University of Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Shigematsu
authors.forename: A
authors.initials: A
authors.lastname: Inoue
authors.forename: M
authors.initials: M
authors.lastname: Hidaka
authors.forename: H
authors.initials: H
authors.lastname: Masaki
authors.forename: T
authors.initials: T
authors.lastname: Uozumi
mesh_terms: D000595:Amino Acid Sequence; D016949:Azospirillum; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000187:drug effects* / Q000235:genetics; D003001:Cloning, Molecular; D004926:Escherichia coli; D015870:Gene Expression; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009586:Nitrogen Fixation / Q000235:genetics*; D010100:Oxygen / Q000494:pharmacology*; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000096:biosynthesis; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000096:biosynthesis / Q000187:drug effects* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; C061338:NifA protein, Bacteria; D011994:Recombinant Proteins; D014157:Transcription Factors; D010100:Oxygen