Is a γ‐Bend in Angiotensinogen the Recognition Element for Cleavage by Renin?

The conformation of angiotensinogen, the natural substrate of the enzyme renin, was investigated by molecular dynamics (MD) and 2D NMR spectroscopic methods. The global minimum of the MD simulation is characterized by three γ-bends (at Arg2, Phe8, and Tyr13) and a tight loop around residues His9, Leu10 and Leu11. MD calculations show further that secondary structural elements such as α-helices or β-turns are energetically unfavourable for angiotensinogen. Sequence-specific 1H resonance assignments for angiotensinogen in DMSO-d6 were made using a combination of 2D-COSY and -NOESY experiments. Based on chemical shifts values, 3JNHα coupling constants, temperature coefficients of the chemical shifts of NH protons and intra- and inter-residue NOEs, two γ-bends are predicted at His9 and Leu10. The two γ-bends do not occur together in a single structure but the molecule probably exists in a mixture of at least two conformations with a γ-bend at either His9 or Leu10.