ISOLATION AND PARTIAL CHARACTERIZATION OF A NEW A-NEUROTOXIN FROM Tityus serrulatus venom

COLOGNA C.T. (1), BERTAZZI D.T. (1), AGUIAR J.F. (2)., VARANDA W.A. (2), ARAÚJO H.S.S. (3), ARANTES, E.C. (1).

(1) Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto – USP. (2) Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto – USP. (3) Departamento de Ciências Fisiológicas, CBME – Universidade Federal de São Carlos.

Scorpion venoms have been extensively studied in the last years because they are a good source of neurotoxins which act on ion channels. Voltage-gated Na+ channel (Nav channel) toxins are mainly responsible for the toxic effects of scorpion envenoming and can be classified into two classes: a- and b-neurotoxins. Scorpion toxins acting on Nav channels lead to an increase in Na+ influx, which in turns can induce membrane depolarization. The aim of the present study was the purification and partial characterization of a new a-neurotoxin from Tityus serrulatus venom (Tsv). The toxin was isolated from Tsv by ion-exchange chromatography on a 2.5 x 63.0 cm column of carboxymethyl cellulose-52, which was equilibrated and eluted with ammonium bicarbonate buffer (pH 7.8). Fraction X was submitted to a reverse-phase (C18) high performance liquid chromatography and fraction X-1 was the new a-neurotoxin. The N-terminal amino acid sequence did not show homology to previously deposited sequences. The purity of toxin X-1 was confirmed by PAGE and SDS-PAGE. In order to verify the effect of X-1 on Na+ currents, the whole cell configuration of the patch clamp technique was used on cells of the Dorsal Root Ganglion of newborn rats. X-1 (10 mM) lead to a significant increase (~90 %) in the decay time constant of inactivation without major effects on the maximal currents at each voltage. The effect is reversible upon washout of the toxin.

KEY WORDS: scorpion venom, neurotoxin, ionic channel, sodium currents.

FINANCIAL SUPPORT:  CNPq.

CORRESPONDENCE TO: Camila Takeno Cologna, Faculdade de Ciências Farmacêuticas de Ribeirão Preto – USP, Av do Café, sn, Ribeirão Preto-SP. Phone: +55 16 3602 4193. Email: camilatcbio@yahoo.com.br