Regulation of the transcriptional activators AnfA and VnfA by metals and ammonium in Azotobacter vinelandii

FEMS Microbiol Lett. 1998 Jul 1;164(1):63-8. doi: 10.1111/j.1574-6968.1998.tb13068.x.


Transcription of the genes encoding molybdenum (Mo)-independent nitrogenases 2 and 3 of Azotobacter vinelandii requires the activators VnfA and AnfA, respectively. The effect of NH4+, Mo, or V (vanadium) was tested on the expression of vnfA-lacZ and anfA-lacZ transcriptional fusions. Mo repressed expression of both fusions whereas NH4+ and V repressed the anfA-lacZ fusion, but not the vnfA-lacZ fusion. Thus the repressive effect on transcription of the anfHDGKOR operon by NH4+, Mo, or V is mediated through their effect on transcription of anfA and the repressive effect of Mo on the vnfHFd and vnfDGK operons is mediated through Mo repression of vnfA transcription. Mo-dependent repression of anfA transcription is influenced but not entirely mediated by the Mo-responsive regulator ModE.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Acetates / pharmacology
  • Azotobacter vinelandii / drug effects*
  • Azotobacter vinelandii / enzymology
  • Azotobacter vinelandii / genetics
  • Bacterial Proteins / drug effects*
  • Bacterial Proteins / genetics
  • Cloning, Molecular
  • DNA-Binding Proteins / drug effects*
  • DNA-Binding Proteins / genetics
  • Gene Expression Regulation, Bacterial / genetics
  • Metals / pharmacology*
  • Molybdenum / pharmacology
  • Trans-Activators / drug effects*
  • Trans-Activators / genetics
  • Vanadium / pharmacology
  • beta-Galactosidase / metabolism


  • Acetates
  • Bacterial Proteins
  • DNA-Binding Proteins
  • Metals
  • Trans-Activators
  • VnfA protein, Azotobacter vinelandii
  • Vanadium
  • Molybdenum
  • beta-Galactosidase
  • ammonium acetate