A TRYPSIN-INHIBITOR FROM SNAIL MEDIC SEEDS ACTIVE AGAINST PEST PROTEASES

A protein trypsin inhibitor from seeds of snail medic (Medicago scutel lata), MsTI, has been purified by ion-exchange chromatography, gel-fil tration chromatography and reverse-phase HPLC. The protein inhibits th e catalytic activity of bovine beta-trypsin, with an apparent K-d of 1 .8 x 10(-9), but exhibits no activity towards bovine alpha-chymotrypsi n. Moreover, MsTI inhibits the trypsin-like proteinase activity presen t in larvae of the crop pests Adoxophyes orana, Hyphantria cunea, Lobe sia botrana and Ostrinia nubilalis. The complete amino acid sequence o f MsTI consists of 62 residues corresponding to a M(r) of 6925. Sequen ce comparison shows that MsTI exhibits significant similarity to other proteins belonging to the Bowman-Birk trypsin inhibitor family, and t he closest identity (81%) with the wound-induced trypsin inhibitor fro m Medicago sativa leaves. Copyright (C) 1997 Elsevier Science Ltd