Skip to main content
padlock icon - secure page this page is secure

Free Content The control of Azorhizobium caulinodans nifA expression by oxygen, ammonia and by the HF-I-like protein, NrfA

Download Article:
The control of Azorhizobium caulinodans nifA expression in response to oxygen and ammonia involves FixLJ, FixK, NtrBC, NtrXY and the HF-I-like protein NrfA. The regulation is thus complex and possibly involves post-transcriptional regulation by NrfA. The coding region of nifA was determined using a translational lacZ fusion and by site-directed mutagenesis to identify which of four in frame AUG codons was used. The major NifA protein is translated from the second AUG codon and is predicted to consist of 613 amino acids. Primer extension analysis showed a major transcript starting 34 bp downstream from the anaerobox in wild-type, nifA, rpoN, ntrC and nrfA strains, but not in a fixK mutant. FixK- and oxygen-dependent transcription of nifA was confirmed by the analysis of four transcriptional nifAlacZ fusions with fusion junctions at positions + 1, + 47, + 110 and + 181 with respect to the start site. Regulation by ammonia was independent of FixK and RpoN, NtrC being only partially required. Thus, there may be another type of nitrogen control that does not involve NtrC in A. caulinodans. NrfA is not required for the initiation of nifA transcription but, most probably, has an effect on nifA mRNA stability and/or translation. NrfA also restores the defect in rpoS translation to an Escherichia coli hfq mutant, indicating that HF-I and NrfA have similar activities in both A. caulinodans and E. coli.
No References
No Citations
No Supplementary Data
No Article Media
No Metrics

Document Type: Original Article

Affiliations: Unité de Physiologie Cellulaire and URA 1300 CNRS, Département des Biotechnologies, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris Cedex 15, France.

Publication date: April 1, 1998

  • Access Key
  • Free content
  • Partial Free content
  • New content
  • Open access content
  • Partial Open access content
  • Subscribed content
  • Partial Subscribed content
  • Free trial content
Cookie Policy
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more