Heme binds to and inhibits the DNA-binding activity of the global regulator FurA from Anabaena sp. PCC 7120

Heme is an iron-containing cofactor that aside from serving as the active group of essential proteins is a key element in the control of many molecular and cellular processes. In prokaryotes, the family of Fur (ferric uptake regulator) proteins governs processes essential for the survival of microorganims such as the iron homeostasis. We show that purified recombinant FurA from Anabaena sp. PCC 7120 interacts strongly with heme in the micromolar range and this interaction affects the in vitro ability of FurA to bind DNA, inhibiting that process in a concentration-dependent fashion. Our results provide the first evidence of the possible involvement of heme in the regulatory function of cyanobacterial Fur.