The binding and transport of alternative metals by transferrin

BACKGROUND: The iron transport protein of the blood plasma, transferrin, is maintained only with about 30% of its capacity to bind Fe(3+) ions; this leaves the protein the potential ability to transport other metal ions from the bloodstream to the tissues. SCOPE OF REVIEW: This review examines the potential role of transferrin to bind and transport alternative metal ions with possible beneficial and deleterious effects. MAJOR CONCLUSIONS: Transferrin has been postulated to play a significant role in transporting Ti(4+), VO(2+) (V(4+)), Cr(3+), Ru(3+), and Bi(3+), all metal ions of potential therapeutic significance. Transferrin may possess a physiological role in the transport of manganese, as the trivalent ion. However, the protein may also play a role in carrying potentially toxic Al(3+) and actinide ions, including Pu(4+), to the tissues. Attempts to use transferrin in the selective removal of low concentrations of specific metal ions from aqueous mixed ions waste streams using a procedure called metalloprotein affinity metal chromatography are discussed. GENERAL SIGNIFICANCE: The binding of alternative metals to transferrins may have therapeutic and toxicological significance. This article is part of a Special Issue entitled Transferrins: Molecular Mechanisms of Iron Transport and Disorders.