Crotalocytin: recognition and purification of a timber rattlesnake platelet aggregating protein

After being envenomated by the timber rattlesnake, a patient was found to have a platelet count of 5000 per microliter, prothrombin time and activated partial thromboplastin time both greater than 150 sec, plasma fibrinogen 0 mg/dl, and fibrinogen split products 2560 microgram/ml. However, this patient did not appear to have acute disseminated intravascular coagulation since coagulation factors II-XII were normal. We postulated that this venom contained, in addition to a fibrinogen clotting enzyme, a platelet activating protein, Crotalocytin. Crotalocytin was purified from crude timber rattlesnake venom by Sephadex G-100 gel-filtration, low ionic strength precipitation, and DEAE-A50 Sephadex chromatography. By sodium dodecyl sulfate gel electrophoresis and gel-filtration Crotalocytin was a single chain polypeptide, molecular weight 55,000. Thrombocytopenia after timber rattlesnake bite appeared to be due to a protein that directly activated platelets. Timber rattlesnake bite mimicked the clinical presentation of disseminated intravascular coagulation.