Vol. 39, No. 4, July 1996 BIOCHEMISTRY and MOLECULAR BIOLOGYINTERNATIONAL Pages 729-740 ISOLATION OF TOXIN TsTX-VI FROM Tityus serrulatus SCORPION VENOM. EFFECTS ON THE RELEASE OF NEUROTRANSMITTERS FROM SYNAPTOSOMES Suely V.Sampaio l, Joaquim Coutinho-Netto2, Eliane C.Arantes 1, Sergio Marangoni3, Benedito Oliveira3 and Jos6 R. Giglio 2. 1Departamento de Amilises Clinicas, Toxicolrgicas e Bromatolrgicas and Departamento de Fisica e Quimica, Faculdade de Ci~ncias Fannac~uticas; 2Departamento de Bioquimica, Faeuldade de Medicina - Universidade de S~o Paulo, 14049-900 Ribeir~o Preto - SP; 3Departamento de Bioquimica, Instituto de Biologia - Unicamp, Campinas - SP, Brazil. Received March 4, 1996 Received after revision May 8, 1996 SUMMARY: A detailed procedure for the purification of Tityustoxin-VI, TsTX-VI, from Tityus serrulatus scorpion venom is described. For comparative purposes, a second toxin, CM-VI, obtained from the same fractionation procedure, was analyzed in parallel. Typical biochemical parameters, such as electrophoretic migration, mol.weight, amino acid composition and N-terminal sequence (first 42 amino acid residues out of a total of approx. 60) were determined for both. Our data showed that CM-VI is identical or extremely homologous to y-toxin (TsTX-I), the highly toxic major toxin from T. serrulatus venom. TsTX-VI was less toxic, although still effective at inducing an allergic reaction, lacrymation and contraction of the hind legs of mice. Both toxins produced a dose dependent release of the neurotransmitters glutamic acid and gamma aminobutyric acid from rat brain synaptosomes, this effect being blocked by tetrodotoxin. INTRODUCTION Synaptosomes represent an excellent tool for studies of the synaptic functions and, together with neurotoxins, have provided important information about the molecular basis of neuronal excitability (1,2). Venom toxins are usually mixed or complexed with other proteins in the same venom. These may be little or even non toxic on basis of pre- established criteria, although not devoid of important physiological effects . An interesting example is the non toxic anti-epileptic peptide Bm-AEP, M r = 8,300, * To whom correspondence should be addressed 729 1039-9712/96/040729-12505.00/0 Copyright © 1996 by Academic Press Australia. All rights of reproduction in any form reserved.