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.
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.
Bagg
A
A
Department of Biochemistry, University of California, Berkeley 94720.
Neilands
J B
JB
D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D005296:Ferrous Compounds / Q000378:metabolism*; D006877:Hydroxamic Acids / Q000378:metabolism; D007502:Iron Chelating Agents / Q000378:metabolism*; D007700:Kinetics; D009876:Operon; D010957:Plasmids; D014176:Protein Biosynthesis; D012097:Repressor Proteins; D014157:Transcription Factors; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D005296:Ferrous Compounds; D006877:Hydroxamic Acids; D007502:Iron Chelating Agents; D012097:Repressor Proteins; D014157:Transcription Factors; C031819:aerobactin