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.
The promoter region of the pColV-K30-encoded operon specifying biosynthesis and transport of the siderophore aerobactin was subjected to deletion analysis to determine the smallest DNA sequence affording iron regulation of a iucA'-'lacZ gene fusion. A 78-base-pair (bp) region containing the main (P1)
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.