The Separation of a Neurotoxin from the Venom of Naja melanoleuca and the Primary Sequence Determination

Abstract

The venom of Naja melanoleuca has been fractionated, first on Sephadex G-50 and the most toxic fraction (judged by the LD50 determined in mice) has been further fractionated on SE-Sephadex C25 at two pH values. Six polypeptide fractions showing single N-terminal amino acid residues have been isolated in quantities sufficient for sequence determination. Of these, all but one are neurotoxins. Three are “long” toxins which are identical up to the 20th residue and can be identified with the “long” toxin, b, already characterized by other workers. A fourth is a “short” toxin, identifiable with toxin d also previously described. The fifth neurotoxic component is different from all components of the venom previously described. It is a “long” toxin, the primary sequence of which has been determined unambiguously, which resembles α-bungarotoxin more closely than do any other “long” toxins.