CRYSTAL-STRUCTURES OF HUMAN PROCATHEPSIN-B AT 3.2 AND 3.3 ANGSTROM RESOLUTION REVEAL AN INTERACTION MOTIF BETWEEN A PAPAIN-LIKE CYSTEINE PROTEASE AND ITS PROPEPTIDE

A wild-type human procathepsin B was expressed, crystallized in two cr ystal forms and its crystal structure determined at 3.2 and 3.3 Angstr om resolution. The structure reveals that the propeptide folds on the cathepsin B surface, shielding the enzyme active site from exposure to solvent. The structure of the enzymatically active domains is virtual ly identical to that of the native enzyme [Mush et al. (1991) EMBO J. 10, 2321-2330]: the main difference is that the occluding loop residue s are lifted above the body of the mature enzyme, supporting the prope ptide structure.