Characterization and 3D model of a new proteinase inhibitor isolated from Stichodactyla helianthus

Protein proteinase inhibitors are widely distributed in living organisms and classified upon their similarities according to sequence, topology, active site localization and the binding mechanism. Proteinase inhibitors from sea anemones are specially interesting as they represent the phylogenetically oldest aprotinin type inhibitors known until now. They can be easily isolated in large quantities. Isoinhibitors with different inhibitory specificity may provide desirable properties for therapeutic uses and for the study of structure-functions relationships. In 1996 we reported the isolation and characterization of the ShPI-I protease inhibitor from the sea anemone Stichodactyla helianthus. Here we report the primary structure and the dissociation constant against trypsin of a new proteinase inhibitor ShPI-2, isolated from the same source. We also discuss a 3D model of the ShPI-2/Trypsin complex.