The nifHDK operon in the free-living nitrogen-fixing bacteria Azospirillum brasilense sequentially comprises genes H, D, K, an 353 bp orf and gene Y.
1. The complete nucleotide sequence of the nitrogenase structural genes from Azospirillum brasilense was determined. Two additional open reading frames of 353 and 683 base pairs were detected downstream of the nifK gene, one of which shows homology to the nifY gene. 2. Structures resembling the consensus nif promoter and NifA-binding motif were found only upstream from the nifH region and an inverted repeat structure located downstream of the nifY gene may be a potential stem-and-loop transcriptional terminator. 3. The nif structural genes of Azospirillum brasilense are transcribed as a single transcription unit and organized as nifHDKorf1Y. NifH, NifD and NifK polypeptides share significant sequence identities when compared to nif structural gene products from other organisms. 4. The three polypeptides are characterized by the presence of highly conserved cysteine residues which may play a role in binding the iron-sulfur cluster.
Passaglia
L M
LM
Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brasil.
Nunes
C P
CP
Zaha
A
A
Schrank
I S
IS
D000595:Amino Acid Sequence; D015806:Azospirillum brasilense / Q000235:genetics*; D001483:Base Sequence; D003062:Codon / Q000235:genetics; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009586:Nitrogen Fixation / Q000235:genetics*; D016366:Open Reading Frames; D009876:Operon; D011401:Promoter Regions, Genetic; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic
D003062:Codon