Fur (ferric uptake regulator) protein is a DNA-binding protein which regulates iron-responsive genes. Fur is a small, 17-kDa, global transcriptional repressor that in the presence of iron regulates functions as diverse as iron acquisition, oxidative stress, and virulence. In Escherichia coli, members of the Fur family regulate the expression of more than 100 genes that function in processes as varied as the biosynthesis and transport of siderophores, the expression of virulence factors, the alleviation of oxidative and NO-induced stress, and the inhibition of ferritin production through the expression of RyhB.