Characterization of three “Birtoxin-like” toxins from the Androctonus amoreuxi scorpion venom

• Published in: Peptides (New York, N.Y. : 1980) N.Y. : 1980), 2011-05, Vol.32 (5), p.911-919
• Main Authors: Abbas, Najwa, Rosso, Jean-Pierre, Céard, Brigitte, Belghazi, Maya, Lebrun, Regine, Bougis, Pierre-Edouard, Martin-Eauclaire, Marie-France
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; amino acids; Androctonus; Animals; Binding; bioassays; Biochemistry; Biochemistry, Molecular Biology; Biological and medical sciences; Birtoxin; brain; Channels; Chromatography, Gel; Chromatography, High Pressure Liquid; disulfide bonds; electrophysiology; Fundamental and applied biological sciences. Psychology; gel chromatography; inhibitory concentration 50; Life Sciences; Male; Mass Spectrometry; Mice; Mice, Inbred C57BL; molecular models; Molecular Sequence Data; Nanostructure; neurons; Peptides; Phylogeny; potassium channels; Rats; Receptors; Residues; reversed-phase high performance liquid chromatography; Scorpion toxin; Scorpion Venoms - chemistry; Scorpion Venoms - metabolism; Sequence Homology, Amino Acid; sodium; Sodium channel; Synaptic Membranes - drug effects; synaptosomes; toxicity; Toxins; venoms; Vertebrates: endocrinology
• ISSN: 0196-9781; 1873-5169
• DOI: 10.1016/j.peptides.2011.02.004

► Three Birtoxin-like (BTX-L) were isolated from the Androctonus amoreuxi (Aam) venom. ► Only one of the peptides, AamBTX-L3, was lethal at nanogram quantities in mouse. ► AamBTX-L3 prevented the binding of the classical β-toxin 125I-Css IV on site 4. ► Site 4 is found on voltage-gated Na + channels of central mammalian neurons. 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 125I-labeled “classical” α- and β-toxins of reference, as well as with the 125I-KTX, a voltage-gated potassium channel blocker. Only AamBTX-L3 was able to prevent the equilibrium binding of the β-toxin 125I-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 125I-Css IV on Na v1.2, 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.