Structure‐conformation relationships of synthetic peptide inhibitors of human renin studied by resonance energy transfer and molecular modeling

The structure-conformation relationships of a series of angiotensinogen6–13 (ANG6–13, His-Pro-Phe-His-Leu-Val-Ile-His) congeners substituted by Nin-For-Trp (Ftr), d-Ftr or Trp at the N-terminus, Tyr at the C-terminus and PheΨ[CH2NH]Phe at the P1-P′1 cleavage site (i.e. Leu10-Val11) were studied using resonance energy transfer coupled with molecular modeling of the peptide conformation using macromolecular energy refinement and dynamics simulation. Average end-to-end intramolecular distances (r) of the peptides in solution were determined by fluorescence spectroscopy. For example, Ac-Ftr-Pro-Phe-His-PheΨ[CH2NH]Phe-Val-Tyr-NH2 (U-70714E) gave an average intramolecular donor (Tyr)-acceptor (Ftr) distance of 16.3 A in aqueous solution. This experimental value was consistent with a distance of 17.9 A determined by molecular modeling of U-70714E to a human renin 3-D structure (developed from known homologous aspartyl protease inhibitor X-ray crystallographic data) followed by simulation of the solution phase conformation of the peptide. An extended backbone secondary structure of U-70714E is suggested from these studies and the relationship(s) of structure-conformation to structure-activity was explored by analysis of several congeners of U-70714E, a potent (IC50= 3.0 × 10−9m) inhibitor of human renin in vitro.