High performance liquid chromatography purification and amino acid sequence of toxins from the muscarinic fraction of Tityus discrepans scorpion venom.

Tityus discrepans venom was fractionated by gel filtration on Sephadex G-50 column. The peptides in fraction II from Sephadex were further purified by high performance liquid chromatography, through a C4 reverse-phase column. Lethality of purified peptides was determined by injection into mice and crabs, and their effects were verified electrophysiologically on frog (Hyla crepitans) sartorius neuromuscular junction. Toxins having retention times between 39.6 and 40.7 min depolarized the muscle membrane and caused acetylcholine release at the endplate. The toxin eluted at 42.67 min increased the frequency of miniature endplate potentials without depolarizing muscle fibres. The four most active toxins were reduced, carboxymethylated and sequenced by automatic Edman degradation and named TdII-1 to II-4. Toxin gamma from Tityus serrulatus venom and the toxins from T. discrepans venom were found to be structurally distinct. TdII-1 to II-4 lack the pancreatic effects of T. serrulatus' toxin gamma; yet, the five toxins act on Na+ channels.