Observation of a tight-turn conformation in a proline-containing inhibitor of renin angiotensin

The solution conformation of renin inhibitor peptide, Pro-His-Pro-Phe-His-Phe-Phe-Val-Tyr-Lys, was established using proton magnetic resonance techniques. As a first step a complete resonance assignment was made in DMSO-d6 using 2D NMR techniques. Some of the backbone NH protons show a very low temperature coefficient, indicating their involvement in intramolecular hydrogen bonding. The 3J(NH-Cα, H) values the inter-residue NOEs, the temperature coefficient of the backbone NH protons and the chemical shift positions indicate the presence of a tight turn in the molecule. A model is proposed, using computer graphics, based on the experimental results