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 angiotensinogen_6–13 (ANG_6–13, 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 PheΨCH₂NH]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-PheΨCH₂NH]Phe-Val-Tyr-NH₂ (U-70714E) gave an average intramolecular donor (Tyr)-acceptor (Ftr) distance of 16.3 Å in aqueous solution. This experimental value was consistent with a distance of 17.9 Å 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.