Peptides related to the active fragment of "proline rich polypeptide", an immunoregulatory protein of the ovine colostrum. Spectroscopic and computer modeling studies.

The preferred solution conformation of the PRP-hexapeptide (Tyr-Val-Pro-Leu-Phe-Pro) and of some of its structural analogues was investigated by NMR-spectroscopy, spectrofluorimetry and computer simulation technic. It was found that the preferred conformation is characterized by cis'-conformation of Pro3 and the gamma-turn on the Leu4-residue: for Val2 and Phe5 a beta-structure seems to be privileged. In such a conformation Val2 and Leu4 residues occupy exactly the same positions in space as residues i and i + 3 in an alpha-helix. It suggests that the PRP-hexapeptide can interact with receptor protein inducing or stabilizing its helical conformation by "knobs into holes" packing.