title: Isolation and characterization of a novel toxin from the venom of the spider Grammostola rosea that blocks sodium channels.
abstract: 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 IC(50) of 2.8+/-0.1 microM, up to a maximum of about 85% at 10 microM. Moreover, the right-shift (+20.1+/-0.4 mV) of the fractional voltage-dependent conductance 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 microM. 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.
authors.affiliation: Instituto de Biotecnologia-Universidad Nacional Autónoma de México-UNAM, Avenida Universidad, 2001 Apartado Postal 510-3, Cuernavaca, Morelos 62210, México.
authors.forename: Herlinda
authors.initials: H
authors.lastname: Clement
authors.forename: George
authors.initials: G
authors.lastname: Odell
authors.forename: Fernando Z
authors.initials: FZ
authors.lastname: Zamudio
authors.forename: Elisa
authors.initials: E
authors.lastname: Redaelli
authors.forename: Enzo
authors.initials: E
authors.lastname: Wanke
authors.forename: Alejandro
authors.initials: A
authors.lastname: Alagón
authors.forename: Lourival D
authors.initials: LD
authors.lastname: Possani
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D045744:Cell Line, Tumor; D002851:Chromatography, High Pressure Liquid; D051379:Mice; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D010802:Phylogeny; D051381:Rats; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D026941:Sodium Channel Blockers / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D015222:Sodium Channels / Q000187:drug effects; D013111:Spider Venoms / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D013112:Spiders / Q000737:chemistry*
chemical_list: D010446:Peptide Fragments; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D013111:Spider Venoms