Conformational analysis and in vitro immunomodulatory and insulinotropic properties of the frog skin host-defense peptide rhinophrynin-27 and selected analogs

Abstract The study investigates conformational analysis and the in vitro cytokine-mediated immunomodulatory and insulin-releasing activities of rhinophrynin-27 (ELRLPEIARPVPEVLPARLPLPALPRN; RP-27), a proline-arginine-rich peptide first isolated from skin secretions of the Mexican burrowing toad Rhinophrynus dorsalis (Rhinophrynidae). In both water and 50% trifluoroethanol-water, the peptide adopts a polyproline type II helical conformation with a high degree of deviation from the canonical collagen-like folding and a pronounced bend in the molecule at the Glu13 residue. Incubation of mouse peritoneal cells with RP-27 significantly (P