The solution structure of three small serine proteinase inhibitors, two natural and one engineered protein, SGCI (Schistocerca gregaria chymotrypsin inhibitor), SGCI[L30R, K31M] and SGTI (Schistocerca gregaria trypsin inhibitor), were determined by homonuclear NMR-spectroscopy. The molecules exhibit di erent speci®cities towards target proteinases, where SGCI is a good chymo-trypsin inhibitor, itsmutant is apotent trypsin inhibitor, and SGTI inhibits both proteinases weakly.
