Structure and Reactivity of Transferrins

This chapter provides an overview of structure and reactivity of transferrins. The transferrins are a family of metal-binding proteins having significant role in biological research. Under physiological conditions, the favored state of iron is Fe(III), but this is prone to rapid hydrolysis at concentrations greater than 10−17M, ultimately leading to the precipitation of insoluble ferric hydroxides. The transferrin family is typified by serum transferrin, the iron transport protein in blood. Serum transferrins appear to be present in all vertebrates so far examined; they have been found in crabs and spiders and appear likely to be widespread also in insects. A second member of the family, lactoferrin, is widespread in the secretory fluids of higher animals, including milk, tears, saliva, mucosal, and genital secretions, and in white blood cells. In species that possess both proteins, lactoferrin is distinguishable from serum transferrin by its higher isoelectric point, its distinct sequence, and different bodily location and functional roles.