The peptide hormone hepcidin is a key homeostatic
regulator of iron metabolism and involved in pathological regulation of iron in
response to infection, inflammation, hypoxia and anaemia. It acts by binding to
the iron exporter ferroportin, causing it to be internalised and degraded;
however, little is known about the structure/activity relationships of the
interaction of hepcidin with ferroportin. Here we show that there are key
residues within the N-terminal region of hepcidin that influence its
interaction with ferroportin, and we explore the structure/function relationships
at these positions. We found that the interaction is primarily hydrophobic with
critical stereochemical requirements at positions 4 and 6. In addition, a
series of hepcidin mutants in which disulfide bonds had been replaced with
diselenide bonds showed no change in biological activity compared to native
hepcidin. We have also explored the effect of backbone cyclisation on stability
and biological activity. The results provide mechanistic insight into the
interaction between hepcidin and ferroportin and identify important constraints
for the development of hepcidin congeners for the treatment of hereditary iron
overload.