A 1H Nuclear‐Magnetic‐Resonance Study of the Solution Conformation of the Isoinhibitor K from Helix pomatia

Abstract

The isoinhibitor K from H. pomatia was investigated by high-resolution PMR at 360 MHz. Detailed studies of the labile protons and the resonances of the aromatic residues indicated extensive homologies between the spatial structures of the snail inhibitor, the basic pancreatic trypsin inhibitor (Kunitz) from bovine tissue and the cow colostrum trypsin inhibitor. Comparison of these 3 homologous inhibitors indicated that the overall flexibility of the globular protein conformation was reduced and its stability with respect to thermal denaturation raised when the content of amino acids with charged side chains was increased. This relation between amino acid composition and stability of the globular solution structure might also be valid for other classes of homologous proteins.