Determining the structure and binding mechanism of oxytocin-Cu complex using paramagnetic relaxation enhancement NMR analysis.

Oxytocin is a neuropeptide that binds copper ions in nature. The structure of oxytocin in interaction with Cu was determined here by NMR, showing which atoms of the peptide are involved in binding. Paramagnetic relaxation enhancement NMR analyses indicated a binding mechanism where the amino terminus was required for binding and subsequently Tyr2, Ile3 and Gln4 bound in that order. The aromatic ring of Tyr2 formed a π-cation interaction with Cu. Oxytocin copper complex structure revealed by paramagnetic relaxation enhancement NMR analyses.