title: Purification and amino acid sequence of a highly insecticidal toxin from the venom of the brazilian spider Phoneutria nigriventer which inhibits NMDA-evoked currents in rat hippocampal neurones.
abstract: A new insecticidal toxin Tx4(5-5) was isolated from the fraction PhTx4 of the venom of the spider Phoneutria nigriventer by reverse phase high performance liquid chromatography (HPLC) and anion exchange HPLC. The complete amino acid sequence determined by automated Edman degradation showed that Tx4(5-5) is a single chain polypeptide composed of 47 amino acid residues, including 10 cysteines, with a calculated molecular mass of 5175 Da. Tx4(5-5) shows 64% of sequence identity with Tx4(6-1), another insecticidal toxin from the same venom. Tx4(5-5) was highly toxic to house fly (Musca domestica), cockroach (Periplaneta americana) and cricket (Acheta domesticus ), producing neurotoxic effects (knock-down, trembling with uncoordinated movements) at doses as low as 50 ng/g (house fly), 250 ng/g (cockroach) and 150 ng/g (cricket). In contrast, intracerebroventricular injections (30 microg) into mice induced no behavioural effects. Preliminary electrophysiological studies carried out on whole-cell voltage-clamped rat hippocampal neurones indicated that Tx4(5-5) (at 1 microM) reversibly inhibited the N-methyl-D-aspartate-subtype of ionotropic glutamate receptor, while having little or no effect on kainate-, alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid- or gamma-aminobutyric acid-activated currents.
authors.affiliation: Departmento de Ciencias Fisiologicas, Universidade Federal do Espirito Santo, Vitoria, ES, Brazil.
authors.forename: S G
authors.initials: SG
authors.lastname: de Figueiredo
authors.forename: M E
authors.initials: ME
authors.lastname: de Lima
authors.forename: M
authors.initials: M
authors.lastname: Nascimento Cordeiro
authors.forename: C R
authors.initials: CR
authors.lastname: Diniz
authors.forename: D
authors.initials: D
authors.lastname: Patten
authors.forename: R F
authors.initials: RF
authors.lastname: Halliwell
authors.forename: J
authors.initials: J
authors.lastname: Gilroy
authors.forename: M
authors.initials: M
authors.lastname: Richardson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D003058:Cockroaches; D004591:Electrophoresis, Polyacrylamide Gel; D006135:Gryllidae; D006624:Hippocampus / Q000187:drug effects; D007306:Insecticides / Q000302:isolation & purification* / Q000633:toxicity; D007928:Lethal Dose 50; D051379:Mice; D008969:Molecular Sequence Data; D009498:Neurotoxins / Q000302:isolation & purification* / Q000633:toxicity; D018408:Patch-Clamp Techniques; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*; D013111:Spider Venoms / Q000302:isolation & purification* / Q000633:toxicity*
chemical_list: D007306:Insecticides; D009498:Neurotoxins; D016194:Receptors, N-Methyl-D-Aspartate; D013111:Spider Venoms; C418408:Tx4(5-5) neurotoxin, Phoneutria nigriventer