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‐ d 6 using 2D NMR techniques. Some of the backbone NH protons show a very low temperature coefficient, indicating their involvement in intramolecular hydrogen bonding. The 3 J (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.