Ferric Uptake Regulation Protein Acts as a Repressor, Employing Iron (II) as a Cofactor to Bind the Operator of an Iron Transport Operon in Escherichia Coli

Biochemistry. 1987 Aug 25;26(17):5471-7. doi: 10.1021/bi00391a039.


The Fur (ferric uptake regulation) protein is a negative regulator of the aerobactin operon and of several other siderophore-mediated, high-affinity iron transport systems in Escherichia coli. The purified Fur protein and a plasmid containing a lacZ fusion to the aerobactin operon were used in conjunction with an in vitro coupled transcription/translation system to demonstrate that the Fur protein requires Fe(II) or certain other divalent metals as a cofactor to negatively regulate expression of the aerobactin operon. In a second set of experiments, using a restriction site protection assay, Fur was shown to bind to and block the aerobactin promoter in a metal-dependent fashion. It is concluded that Fur acts as a classical negative repressor that, under in vivo conditions, uses ionic Fe(II) as a corepressor. Our results support the hypothesis [Williams, R.J.P. (1982) FEBS Lett. 140, 3-10] that prokaryotic cells may contain a standing pool of free or loosely bound Fe(II) that is capable of acting in a regulatory capacity.

Publication types

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

MeSH terms

  • Bacterial Proteins / genetics*
  • Bacterial Proteins / isolation & purification
  • Bacterial Proteins / metabolism
  • Escherichia coli / genetics*
  • Escherichia coli / growth & development
  • Escherichia coli / metabolism
  • Ferrous Compounds / metabolism*
  • Hydroxamic Acids / metabolism
  • Iron Chelating Agents / metabolism*
  • Kinetics
  • Operon*
  • Plasmids
  • Protein Biosynthesis
  • Repressor Proteins*
  • Transcription Factors*
  • Transcription, Genetic


  • Bacterial Proteins
  • Ferrous Compounds
  • Hydroxamic Acids
  • Iron Chelating Agents
  • Repressor Proteins
  • Transcription Factors
  • aerobactin