INVESTIGATIONS ON THE ANTIGENICITY OF SNAKE VENOMS

The chemical composition of viperotoxin, the neurotoxic protein isolated from the venom of Vipera palestinae has been determined. Viperotoxin is composed of one polypeptide chain cross-linked intramolecularly by three disulfide bridges. Lysine is in the amino-terminal position, and proline in the carboxy-terminal position of the viperotoxin chain. Vipera palestinae hemorrhagin has been purified and isolated. Further tests have established that the hemorrhagin is an acidic protein with an estimated molecular weight of 44, 000. The purified hemorrhagin has gelatinase activity which can be inhibited by soybean trypsin inhibitor or DFP, while leaving the hemorrhagic activity intact. Among the possible explanations of this functional differentiation one may consider the association of two protein molecules thus far inseparable by chemical and physical methods, one molecule with two distinct active sites, or selective blocking of a part of one active center having two distinct biological activities. Purified neurotoxin of V. palestinae viperotoxin was bound to tritiated alanine. This binding did not alter either the toxicity or the antigenicity of viperotoxin. In vivo distribution of sublethal doses of the labelled viperotoxin were followed in the various tissues of mice. The highest level of toxin was found in the kidneys, followed by liver, lungs and spleen, and a surprisingly low concentration in the brain. The clearance rate from the blood was slow.