FUR system

Iron is an essential element in the development of E. coli, but also, it can be toxic and E. coli can be killed, if iron is absorbed in high quantity. Using the ferric-uptake regulator protein (Fur), bacteria developed an advanced system to regulate their iron homeostasis.

FUR protein (Ferric Uptake Regulator)

The Fur protein is a transcriptional repressor of more than 90 genes involved, in majority, in iron homeostasis (Revue + “Iron and metal regulation in bacteria”, Klaus Hantke). It plays an important role in the control of the intracellular concentration of iron in E. coli.

Fur acts as a positive repressor in presence of ferrous ion (Fe2+), its co-repressor. Then, Fe2+ binds to the Fur protein (one ferrous ion per subunit of Fur), it will lead to a structural modification and induce the dimerization of Fur and Fe2+. Then the homodimeric Fur-Fe2+ complex will bind to the DNA in a Fur Binding Site and inhibit the mRNA transcription. In absence of Fe2+, a disinhibiting effect occurs and mRNA transcription can be done.

AJOUTER SCHEMA FUR BINDING SITE

FUR binding site architecture

Inverter system

Siderophores biosynthesis