CRYSTAL-STRUCTURE OF A CARICAIN D158E MUTANT IN COMPLEX WITH E-64

The structure of the D158E mutant of caricain (previously known as pap aya protease omega) in complex with E-64 has been determined at 2.0 An gstrom resolution (overall R factor 19.3%). The structure reveals that the substituted glutamate makes the same pattern of hydrogen bonds as the aspartate in native caricain, This was not anticipated since in t he native structure there is insufficient room to accommodate the glut amate side chain. The glutamate is accommodated in the mutant by a loc al expansion of the structure demonstrating that small structural chan ges are responsible for the change in activity.