Purification from Vipera lebetina (desert adder) venom of a protein that depletes human complement

A rapid and efficient procedure for purification from Vipera lebetina venom of a low molecular weight anticomplement protein is described. The procedure used gel filtration on Superose 12, followed by ion-exchange chromatography on a Mono Q column. The purified protein migrated on SDS-PAGE as a single band of about 25,000 Da under nonreducing conditions and as a band of 16,000 Da under reducing conditions. Its isoelectric point was estimated to be 7.6 +/- 0.1. The isolated Vipera lebetina protein was found to decrease the hemolytic activity in human serum measured by assays for classical pathway and alternative pathway activation. The loss of the complement activity could be ascribed, at least in part, to a proteolytic cleavage of the alpha chains of C3 and C4. This protein was also found to be without action on human blood coagulation and on purified fibrinogen and Factor B.