CRYSTALLIZATION AND PRELIMINARY CRYSTALLOGRAPHIC ANALYSIS OF ANTISTASIN, A LEECH-DERIVED INHIBITOR OF BLOOD-COAGULATION FACTOR-XA

The salivary gland of the Mexican leech Haementeria officinalis contains a 15 kDa protein which is a potent and selective inhibitor of factor Xa. It inhibits not only blood coagulation, but also metastasis. A gene, coding for a sequence similar to published antistasin sequences, has been synthesized and expressed in Chinese hamster ovary (CHO) cells. The recombinant protein was purified and crystallized at pH 6.0, using 31% ammonium sulfate as a precipitant. the crystals diffract at least to 2.8 Å. The spacegroup is I422 with a = b = 77.7 Å and c = 88.4 Å. The crystals contain 42% solvent and one protein molecule in the asymmetric unit. A search for heavy atom derivatives is in progress. © 1993 Academic Press, Inc.