title: Characterization of three "Birtoxin-like" toxins from the Androctonus amoreuxi scorpion venom.
abstract: The venom of the North African scorpion Androctonus amoreuxi (Aam) was analyzed using a combination of gel filtration, C18 reverse phase HPLC together with mass spectrometry analysis and bioassays. Three novel Birtoxin-like (BTX-L) peptides of 58 amino acid residues comprising three disulfide bridges were isolated and chemically characterized. One peptide, AamBTX-L3, induced serious toxic symptoms in mice and was lethal at nanogram quantities using intracerebroventricular injection. The three BTX-L peptides were tested in competition experiments on rat brain synaptosomes against the (125)I-labeled "classical" α- and β-toxins of reference, as well as with the (125)I-KTX, a voltage-gated potassium channel blocker. Only AamBTX-L3 was able to prevent the equilibrium binding of the β-toxin (125)I-Css IV to its receptor site 4 with a IC(50) value of 189 nM. Even if previous electrophysiological data allowed the classification of other BTX-L peptides among the β-type toxins, this report clearly shows that AamBTX-L3 is pharmacologically a β-toxin, which recognizes the voltage-gated Na(+) (Na(v)) channels from central mammalian neurons. In order to uncover the residues functionally essential for interaction between the AamBTX-L3 with the putative receptor site of (125)I-Css IV on Na(v)1.2, molecular models of the three novel Aam BTX-L molecules were made and their surfaces were compared to the already described Css IV biologically interactive surfaces. A hypothesis is given that in BTX-L3, three residues found in the α-helix play a key role during target binding.
authors.affiliation: CNRS UMR6231, CRN2M, Université de la Méditerranée, Faculté de Médecine secteur Nord, CS80011, Bd Pierre Dramard, F-13344 Marseille Cedex 15, France.
authors.forename: Najwa
authors.initials: N
authors.lastname: Abbas
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Rosso
authors.forename: Brigitte
authors.initials: B
authors.lastname: Céard
authors.forename: Maya
authors.initials: M
authors.lastname: Belghazi
authors.forename: Regine
authors.initials: R
authors.lastname: Lebrun
authors.forename: Pierre-Edouard
authors.initials: PE
authors.lastname: Bougis
authors.forename: Marie-France
authors.initials: MF
authors.lastname: Martin-Eauclaire
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D008297:Male; D013058:Mass Spectrometry; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D010802:Phylogeny; D051381:Rats; D012604:Scorpion Venoms / Q000737:chemistry* / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013570:Synaptic Membranes / Q000187:drug effects
chemical_list: D012604:Scorpion Venoms; C440191:birtoxin