EXPRESSION OF HUMAN CATHEPSIN-K IN PICHIA-PASTORIS AND PRELIMINARY CRYSTALLOGRAPHIC STUDIES OF AN INHIBITOR COMPLEX

Cathepsin K is a cysteine protease of the papain family, which is pred ominantly expressed in osteoclasts, and is regarded as a key protease in bone remodeling. To facilitate structural studies of the protein, t he wild-type sequence of the protease has been mutated so as to replac e a potential N-glycosylation site. We have expressed the mutant human cathepsin K to 190 mg/5 L using the Pichia pastoris expression system . Cathepsin K was inactivated with the mechanism-based inhibitor, APC3 328, and crystallized from magnesium formate. A 2.2 Angstrom X-ray dat a set has been collected on crystals belonging to space group P2(1)2(1 )2(1), with a = 41.66 Angstrom, b = 51.41 Angstrom, and c = 107.72 Ang strom. There is most likely one molecule per asymmetric unit.