Isolation and characterization of a novel toxin from the venom of the spider Grammostola rosea that blocks sodium channels

This communication reports the chemical and physiological characterization of a novel peptide (GrTx1) isolated from the venom of the rosean-tarantula Grammostola rosea. This component was one among more than 15 distinct components separated from the soluble venom by high-performance liquid chromatography (HPLC). GrTx1 has 29 amino-acid residues, compactly folded by three disulfide bridges with a molecular weight of 3697 Da. Here we show that this peptide blocks Na+ currents of neuroblastoma F-11 cells with an IC50 of 2.8 +/- 0.1 mu M, up to a maximum of about 85% at 10 mu M. M oreover, the right-shift (+ 20.1 +/- 0.4 mV) of the fractional voltage-dependent cond uctance could be also compatible with a putative gating-modifier mechanism. No effects were seen on common K+ channels, such as K(v)1.1 and 1.4, using concentrations of toxin up to 10 mu M. Sequence analysis reveals that GrTx1 is closely related to other spider toxins reported to affect various distinct ion channel functions. A critical analysis of this study suggests the necessity to search for other potential receptor sites in order to establish the preferred specificity of these kind of peptides. (c) 2007 Elsevier Ltd. All rights reserved.