Comparison of the 25-amino acid peptide sequences. The sequences for hepcidin are from mammals (A) and various fish species (B). In the putative consensus amino acid sequence, the X is for any residue and Y for a neutral residue. The conserved cysteines are shaded and the bold underlined residues are those characteristics of the iron-regulatory peptides. In the flounder and bass hepcidin peptides, an additional G residue is present between residues 18 and 19.