Peptides based on the reactive center loop of Manduca sexta serpin-3 block its protease inhibitory function

摘要: One innate immune response in insects is the proteolytic activation of hemolymph prophenoloxidase (proPO), regulated by protease inhibitors called serpins. In inhibition reaction serpins, a cleaves peptide bond solvent-exposed reactive center loop (RCL) serpin, and serpin undergoes conformational change, incorporating amino-terminal segment RCL into β-sheet A as new strand. This results an irreversible inhibitory complex with protease. We synthesized four peptides sequences from hinge region Manduca sexta serpin-3 found they were able to block activity, resulting suppression protease-serpin formation. An RCL-derived sequence Ser-Val-Ala-Phe-Ser (SVAFS) displayed robust blocking activity against serpin-3. Addition acetyl-SVAFS-amide led unregulated proPO activation. Serpin-3 associated Ac-SVAFS-COO- had altered circular dichroism spectrum enhanced thermal resistance change secondary structure, indicating that these two molecules formed binary complex, most likely insertion A. The interference may lead possibilities "silencing" arthropod serpins unknown functions for investigation their physiological roles.