Fur (ferric uptake regulation) protein interaction with target DNA: comparison of gel retardation, footprinting and electron microscopy analyses.

Fur-DNA interactions were analyzed within the regulatory regions of aerobactin and hemolysin operons by a combination of biochemical and ultrastructural methods. Cartography of the Fur binding sites, carried out from electron micrographs, agreed with the data obtained by DNase I footprinting. Visualization of the complexes confirmed the specificity and metal-dependence of Fur binding and demonstrated that the protein polymerizes on its binding sites. Such a polymerization could be involved in the repression process of the bacterial regulator.