Crystallization and preliminary diffraction data of a platelet-aggregationinhibitor from the venom of Agkistrodon piscivorus piscivorus (North American water moccasin)

Applaggin (Agkistrodon piscivorus piscivorus platelet-aggregation inhibitor ) is a potent inhibitor of blood platelet aggregation derived from the veno m of the North American water moccasin, The protein consists of 71 amino ac ids, is rich in cysteines, contains the sequence-recognition site of adhesi on proteins at positions 50-52 (Arg-Gly-Asp) and shares high sequence homol ogy with other snake-venom disintegrins such as echistatin, kistrin and tri gramin, Single crystals of applaggin have been grown and X-ray diffraction data have been collected to a resolution of 3.2 Angstrom. The crystals belo ng to space group P4(1)2(1)2 (or its enantiomorph), with unit-cell dimensio ns a = b = 63.35, c = 74.18 Angstrom and two molecules per asymmetric unit. Molecular replacement using models constructed from the NMR structures of echistatin and kistrin has not been successful in producing a trial structu re for applaggin.