Characterization of the transition-metal-binding properties of hepcidin

Accumulating evidence suggests that hepcidin, a 25-residue peptide hormone, is the master regulator of iron metabolism. Further evidence suggests that the five N-terminal amino acids are crucial for mediating its biological function. With a histidine residue at position 3, this region also has the potential to bind bivalent metal ions. To characterize this hepcidin metal interaction in detail, the present study utilizes electrospray MS to measure the binding of a range of metal ions to wild-type and mutant human and murine hepcidins. In addition, the biological effects of these point mutations were tested on Caco-2 and HEK-293T human cell lines and in mice. Our results show that hepcidin-25 can form complexes with copper, nickel and zinc; however, we failed to detect any hepcidin-25 binding to either ferric or ferrous ions. The greatest affinity observed was between hepcidin-25 and copper with a dissociation constant