A new type of toxin in the venom of snakes of the genus Atractaspis (Atractaspidinae).

The venom of Atractaspis is unique in having a large percentage of both high and low molecular weight components. Its Sephadex G-50 S5 fraction appears to represent a new type of toxin that contains 17-18 Asx, 13-14 Cys and 10-11 Glx out of a total of 72-78 amino acids. The N-terminal of this toxin does not seem to resemble any of the known toxins. The overall lethal potency of the venom is very high; i.v. injections of 5 microgram of venom or 1 microgram of fractions S5 or S6 per mouse causes death within minutes. The results of the present study corroborate previous findings that suggested a separate grouping of the snakes genus Atractaspis at the subfamilial or familial level.