A suggested role for copper in the biological activity of neuropeptides

We have shown that a proline residue in the second or third position of a tetrapeptide chain acts as a 'break-point' to Cu(II) coordination dividing the peptide chain into two parts which coordinate independently. Proline also encourages a beta-conformation for the peptide chain presenting the terminal residues in a suitable conformation to form an abnormally large chelate ring. Many neuropeptides contain proline residues and it is likely that Cu(II) ions assist in holding these peptide molecules in the biologically favourable beta-conformation by bridging across the ends of the chain.