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Mohamed El Ayeb - One of the best experts on this subject based on the ideXlab platform.
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Inhibition of human Kv3.1 current expressed in Xenopus oocytes by the toxic venom fraction of Androctonus australis hector
Archives of pharmacal research, 2013Co-Authors: Amani Cheikh, Rym Benkhalifa, Zied Landoulsi, Imen Chatti, Mohamed El AyebAbstract:AahG50, the toxic fraction of Androctonus australis hector venom, was studied on human Kv3.1 channels activation, stably expressed in Xenopus oocytes using the two-electrode voltage clamp technique. AahG50 reduced Kv3.1 currents in a reversible concentration-dependent manner, with an IC50 value and a Hill coefficient of 40.4 ± 0.2 μg/ml and 1.3 ± 0.05, respectively. AahG50 inhibited IKv3.1 without modifying the current activation kinetics. The AahG50-induced inhibition of Kv3.1 channels was voltage-dependent, with a gradual increase at lower concentrations and over the voltage range of channels opening. However, at higher concentrations, the inhibition exhibited voltage dependence only in the first range of channels opening from −20 to +10 mV, but demonstrates a low degree of voltage-dependence when channels are fully activated. In the literature, toxins have previously been isolated from AahG50, KAaH1 and KAaH2 and were reported not to have any effect on IKv3.1. The present article’s findings suggest that AahG50 may contain a peptidic component active on Kv3.1 channels, which inhibits IKv3.1 in a selective manner.
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First chemical synthesis of a scorpion α‐toxin affecting sodium channels: The Aah I toxin of Androctonus australis hector
Journal of peptide science : an official publication of the European Peptide Society, 2004Co-Authors: Sarrah M'barek, Pascal Mansuelle, Christiane Devaux, Ziad Fajloun, Sandrine Cestèle, Amor Mosbah, Besma Jouirou, Massimo Mantegazza, Jurphaas Van Rietschoten, Mohamed El AyebAbstract:Aah I is a 63-residue alpha-toxin isolated from the venom of the Buthidae scorpion Androctonus australis hector, which is considered to be the most dangerous species. We report here the first chemical synthesis of Aah I by the solid-phase method, using a Fmoc strategy. The synthetic toxin I (sAah I) was renatured in DMSO-Tris buffer, purified and subjected to thorough analysis and comparison with the natural toxin. The sAah I showed physico-chemical (CD spectrum, molecular mass, HPLC elution), biochemical (amino-acid composition, sequence), immunochemical and pharmacological properties similar to those of the natural toxin. The synthetic toxin was recognized by a conformation-dependent monoclonal anti-Aah I antibody, with an IC50 value close to that for the natural toxin. Following intracerebroventricular injection, the synthetic and the natural toxins were similarly lethal to mice. In voltage-clamp experiments, Na(v) 1.2 sodium channel inactivation was inhibited by the application of sAah I or of the natural toxin in a similar way. This work describes a simple protocol for the chemical synthesis of a scorpion alpha-toxin, making it possible to produce structural analogues in time.
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Quantitative variability in the biodistribution and in toxinokinetic studies of the three main alpha toxins from the Androctonus australis hector scorpion venom
Toxicon : official journal of the International Society on Toxinology, 2004Co-Authors: Christiane Devaux, Mohamed El Ayeb, Olivier Clot-faybesse, Besma Jouirou, Herve RochatAbstract:Scorpion stings represent a medical problem in numerous countries. The scorpion Androctonus australis hector produces three alpha toxins (Aah I to III), which are responsible for most of the lethality in mammals. These toxins act on sodium channel and do not cross-react immunologically. We used RIA and ELISA to measure the concentrations of these three toxins in plasma, urine and different organs after i.v. and s.c. injections of water extracts of venoms in rabbits or mice. In both animals, the toxins rapidly appeared in plasma after s.c. injection as it was previously described for the whole venom. However, the toxins disappeared from the blood more quickly than did other main components of the venom. Thus, serotherapy must be initiated immediately to prevent the toxin from reaching its target. We also detected the toxins in urine, kidneys, heart and lungs, but not in the brain. However, the concentration of Aah II was always lower than that of Aah I. Analysis of five samples of venom collected in different areas of southern Tunisia showed that a large polymorphism exists for the three toxins. This is yet another difficulty for serotherapy as there is no cross-antigenicity between them.
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Immunized camel sera and derived immunoglobulin subclasses neutralizing Androctonus australis hector scorpion toxins.
Toxicon : official journal of the International Society on Toxinology, 2003Co-Authors: Fatma Meddeb-mouelhi, Balkiss Bouhaouala-zahar, Zakaria Benlasfar, Mohamed Hammadi, Thouraya Mejri, Mekki Moslah, Habib Karoui, Touhami Khorchani, Mohamed El AyebAbstract:Scorpion envenoming is a real health problem. The only specific treatment is immunotherapy with antibodies from immunized horses. The severity of scorpion envenoming and the rapid diffusion of the toxins into the blood compartment require an improvement of the present antivenom therapy. In this study, we report successful immunization of dromedaries (Camelus dromedarius) against the small weakly antigenic neurotoxins of Androctonus australis hector scorpion. Camel immune sera was tested for its specific antigenic reactivity and neutralizing capacity against Aah toxic fraction and AahII toxin. We demonstrate that a substantial proportion of polyclonal heavy chain antibodies bind to Aah toxins and in particular to AahII, the most toxic one scorpion venom component. Furthermore, we show that both dromedary sera and heavy chain antibody subclasses are capable of neutralizing the toxicity of Aah toxins in mice.
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Purification, characterization and molecular modelling of two toxin-like proteins from the Androctonus australis Hector venom.
European journal of biochemistry, 2000Co-Authors: Najet Srairi-abid, Herve Rochat, Pascal Mansuelle, Francois Sampieri, Thouraya Mejri, Habib Karoui, Mohamed El AyebAbstract:Two toxin-like proteins (AahTL1 and AahTL3) were purified from the venom of the scorpion Androctonus australis Hector (Aah). AahTL1 and AahTL3 are the first non toxic proteins cross-reacting with AahI toxins group which indicates that these proteins can be used as a model of vaccins. In order to study structure-function relationships, their complete amino-acid sequences (66 residues) were determined, by automated Edman degradation. They show more than 50% of similarity with both AahI and AahIII antimammal toxins. Three-dimensional structural models of AahTL1 and AahTL3 constructed by homology suggest that the two proteins are structurally similar to antimammal scorpion alpha-toxins specific to voltage dependent Na+ channels. The models showed also that amino-acid changes between potent Aah toxins and both AahTL1 and AahTL3 disrupt the electrostatic potential gradient at their surface preventing their interaction with the receptor, which may explain their non toxicity.
Herve Rochat - One of the best experts on this subject based on the ideXlab platform.
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Reduction and reoxidation of the neurotoxin II from the scorpion Androctonus australis Hector
International Journal of Peptide and Protein Research, 2009Co-Authors: Jean-marc Sabatier, Patrick Fourquet, Herve Darbon, Herve Rochat, Jurphaas Van RietschotenAbstract:: Reoxidation of the totally reduced scorpion neurotoxin II from Androctonus australis Hector (four disulfide bridges) has been investigated. The totally reduced toxin was highly insoluble in neutral and alkaline conditions, which prevented the use of the usual air oxidation process for renaturation. We tested a new method in which the reduced molecules were first solubilized in 10% (v/v) acetic acid and then oxidized by air through dialysis against a series of buffers with a slow pH gradient from 2.2 to 7.0 or 8.0. In this system, up to 95% of the protein was recovered in solution. Addition of reduced and oxidized glutathione accelerated refolding and also permitted a better recovery of fully active peptide as measured by both toxicity to mice and ability to displace 125I radiolabeled toxin II from its binding site on rat brain synaptosomal fractions. The reoxidation reaction could also be monitored directly by high pressure liquid chromatography. A strong effect of guanidine hydrochloride concentration as well as the temperature was observed both on the solubility of the reoxidation intermediates and on the refolding pathway. Finally, the method used, i.e. dialysis reoxidation with a pH gradient from 2.2 to 8.0 in 0.1 M sodium phosphate, 0.1 M sodium chloride, 20 mM guanidine hydrochloride, 1 mM oxidized and reduced glutathione allowed regeneration in high yield (70%) of a reoxidized toxin form indistinguishable from the native toxin. A minor stable and inactive molecular species (about 30%) showing a difference in mobility by electrophoresis was also detected.
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Covalent structure of the insect toxin of the North African scorpion Androctonus australis Hector.
International journal of peptide and protein research, 2009Co-Authors: Herve Darbon, Charles Kopeyan, E. Zlotkin, J. Van Rietschoten, Herve RochatAbstract:The complete covalent structure of the insect toxin purified from the venom of the North-African scorpion Androctonus australis Hector was described. Its amino acid sequence was established by phenylisothiocyanate degradation of several protein derivatives and proteolytic fragments in a liquid protein sequencer using either a "protein" or a "peptide" program. The position of the four disulfide bridges were deduced by analysis of proteolytic peptides before and after diperformic oxidation, and by partial labeling of the half cystine residues with [14C]-iodoacetic acid and determining the specific radioactivities of the S-[14C]-carboxymethylated phenylthiohydantoin cysteines. The sequences of the insect and mammal toxins from scorpions can be aligned with homology with the positions of seven half-cystine residues as registers. The mammal and insect toxins have three disulfide bridges at homologous positions. The mammal and insect toxins have three disulfide bridges at homologous positions. The fourth bridge is different in that Cys12 in mammal toxin II is replaced by Cys38 in the insect toxin. It is likely that the position of the disulfide bridges is the same for all scorpion neurotoxins active on mammals. We believe that the shift of one half-cystine residue in the insect toxin may induce a conformational change in the structure of the protein, which, in turn, may partially account for the total specificity of this toxin for insect nervous system.
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Quantitative variability in the biodistribution and in toxinokinetic studies of the three main alpha toxins from the Androctonus australis hector scorpion venom
Toxicon : official journal of the International Society on Toxinology, 2004Co-Authors: Christiane Devaux, Mohamed El Ayeb, Olivier Clot-faybesse, Besma Jouirou, Herve RochatAbstract:Scorpion stings represent a medical problem in numerous countries. The scorpion Androctonus australis hector produces three alpha toxins (Aah I to III), which are responsible for most of the lethality in mammals. These toxins act on sodium channel and do not cross-react immunologically. We used RIA and ELISA to measure the concentrations of these three toxins in plasma, urine and different organs after i.v. and s.c. injections of water extracts of venoms in rabbits or mice. In both animals, the toxins rapidly appeared in plasma after s.c. injection as it was previously described for the whole venom. However, the toxins disappeared from the blood more quickly than did other main components of the venom. Thus, serotherapy must be initiated immediately to prevent the toxin from reaching its target. We also detected the toxins in urine, kidneys, heart and lungs, but not in the brain. However, the concentration of Aah II was always lower than that of Aah I. Analysis of five samples of venom collected in different areas of southern Tunisia showed that a large polymorphism exists for the three toxins. This is yet another difficulty for serotherapy as there is no cross-antigenicity between them.
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In vivo neurotoxicity of Androctonus australis hector scorpion venom: evidence that the supra-thoracic nervous system is not implicated in the clinical manifestations.
Toxicon : official journal of the International Society on Toxinology, 2001Co-Authors: O. Clot-faybesse, Herve Rochat, Christiane Devaux, Régis GuieuAbstract:The severity of scorpion stings is related to the highly active neurotoxins in the venom. In this study, rats whose supra-spinal central nervous system was deprived of its peripheral connections were experimentally poisoned by the venom of Androctonus australis hector scorpion. Clinical signs of severity were not modified when the rats had previously undergone high medullar section. These results suggest that the supra-thoracic nervous system is not implicated in the neurotoxicity manifestations of scorpion envenomation.
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Purification, characterization and molecular modelling of two toxin-like proteins from the Androctonus australis Hector venom.
European journal of biochemistry, 2000Co-Authors: Najet Srairi-abid, Herve Rochat, Pascal Mansuelle, Francois Sampieri, Thouraya Mejri, Habib Karoui, Mohamed El AyebAbstract:Two toxin-like proteins (AahTL1 and AahTL3) were purified from the venom of the scorpion Androctonus australis Hector (Aah). AahTL1 and AahTL3 are the first non toxic proteins cross-reacting with AahI toxins group which indicates that these proteins can be used as a model of vaccins. In order to study structure-function relationships, their complete amino-acid sequences (66 residues) were determined, by automated Edman degradation. They show more than 50% of similarity with both AahI and AahIII antimammal toxins. Three-dimensional structural models of AahTL1 and AahTL3 constructed by homology suggest that the two proteins are structurally similar to antimammal scorpion alpha-toxins specific to voltage dependent Na+ channels. The models showed also that amino-acid changes between potent Aah toxins and both AahTL1 and AahTL3 disrupt the electrostatic potential gradient at their surface preventing their interaction with the receptor, which may explain their non toxicity.
Christiane Devaux - One of the best experts on this subject based on the ideXlab platform.
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First chemical synthesis of a scorpion α-toxin affecting sodium channels: The Aah I toxin of Androctonus australis hector
Journal of Peptide Science, 2004Co-Authors: Sarrah M'barek, Pascal Mansuelle, Christiane Devaux, Ziad Fajloun, Sandrine Cestèle, Amor Mosbah, Besma Jouirou, Massimo Mantegazza, Jurphaas Van Rietschoten, Mohamed El AyebAbstract:Aah I is a 63-residue alpha-toxin isolated from the venom of the Buthidae scorpion Androctonus australis hector, which is considered to be the most dangerous species. We report here the first chemical synthesis of Aah I by the solid-phase method, using a Fmoc strategy. The synthetic toxin I (sAah I) was renatured in DMSO-Tris buffer, purified and subjected to thorough analysis and comparison with the natural toxin. The sAah I showed physico-chemical (CD spectrum, molecular mass, HPLC elution), biochemical (amino-acid composition, sequence), immunochemical and pharmacological properties similar to those of the natural toxin. The synthetic toxin was recognized by a conformation-dependent monoclonal anti-Aah I antibody, with an IC50 value close to that for the natural toxin. Following intracerebroventricular injection, the synthetic and the natural toxins were similarly lethal to mice. In voltage-clamp experiments, Na(v) 1.2 sodium channel inactivation was inhibited by the application of sAah I or of the natural toxin in a similar way. This work describes a simple protocol for the chemical synthesis of a scorpion alpha-toxin, making it possible to produce structural analogues in time.
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First chemical synthesis of a scorpion α‐toxin affecting sodium channels: The Aah I toxin of Androctonus australis hector
Journal of peptide science : an official publication of the European Peptide Society, 2004Co-Authors: Sarrah M'barek, Pascal Mansuelle, Christiane Devaux, Ziad Fajloun, Sandrine Cestèle, Amor Mosbah, Besma Jouirou, Massimo Mantegazza, Jurphaas Van Rietschoten, Mohamed El AyebAbstract:Aah I is a 63-residue alpha-toxin isolated from the venom of the Buthidae scorpion Androctonus australis hector, which is considered to be the most dangerous species. We report here the first chemical synthesis of Aah I by the solid-phase method, using a Fmoc strategy. The synthetic toxin I (sAah I) was renatured in DMSO-Tris buffer, purified and subjected to thorough analysis and comparison with the natural toxin. The sAah I showed physico-chemical (CD spectrum, molecular mass, HPLC elution), biochemical (amino-acid composition, sequence), immunochemical and pharmacological properties similar to those of the natural toxin. The synthetic toxin was recognized by a conformation-dependent monoclonal anti-Aah I antibody, with an IC50 value close to that for the natural toxin. Following intracerebroventricular injection, the synthetic and the natural toxins were similarly lethal to mice. In voltage-clamp experiments, Na(v) 1.2 sodium channel inactivation was inhibited by the application of sAah I or of the natural toxin in a similar way. This work describes a simple protocol for the chemical synthesis of a scorpion alpha-toxin, making it possible to produce structural analogues in time.
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Quantitative variability in the biodistribution and in toxinokinetic studies of the three main alpha toxins from the Androctonus australis hector scorpion venom
Toxicon : official journal of the International Society on Toxinology, 2004Co-Authors: Christiane Devaux, Mohamed El Ayeb, Olivier Clot-faybesse, Besma Jouirou, Herve RochatAbstract:Scorpion stings represent a medical problem in numerous countries. The scorpion Androctonus australis hector produces three alpha toxins (Aah I to III), which are responsible for most of the lethality in mammals. These toxins act on sodium channel and do not cross-react immunologically. We used RIA and ELISA to measure the concentrations of these three toxins in plasma, urine and different organs after i.v. and s.c. injections of water extracts of venoms in rabbits or mice. In both animals, the toxins rapidly appeared in plasma after s.c. injection as it was previously described for the whole venom. However, the toxins disappeared from the blood more quickly than did other main components of the venom. Thus, serotherapy must be initiated immediately to prevent the toxin from reaching its target. We also detected the toxins in urine, kidneys, heart and lungs, but not in the brain. However, the concentration of Aah II was always lower than that of Aah I. Analysis of five samples of venom collected in different areas of southern Tunisia showed that a large polymorphism exists for the three toxins. This is yet another difficulty for serotherapy as there is no cross-antigenicity between them.
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immunodosage rapide des toxines individuelles du venin d Androctonus australis
Bulletin De La Societe De Pathologie Exotique, 2002Co-Authors: Nicolas Aubrey, Christiane Devaux, Philippe BillialdAbstract:La mise en place d'une immunotherapie passive efficace des envenimations scorpioniques est facilitee par le dosage prealable des toxines circulantes chez les patients envenimes. Actuellement, les tests ELISA utilises en routine ne permettent que le dosage du venin total, sans distinction des toxines qui le composent et dont la diffusion tissulaire est variable. En prenant comme modele l'une des trois toxines responsables des effets letaux du venin du scorpion Androctonus australis hector (Aahl), nous avons developpe un test ELISA sandwich base sur l'utilisation d'un fragment d'anticorps recombinant (scFv) constitue des domaines variables de l'IgG monoclonale 9C2 couple a un decapeptide affin pour la streptavidine. L'immunoconjugue scFv/Strep-tag a ete prepare par genie genetique. Il est produit dans le periplasme de bacteries recombinantes, de facon reproductible, sous une forme soluble, a faible cout avec un rendement, apres purification, de 0,8 mg/L de culture bacterienne. La proteine recombinante, de petite taille (28 kDa), est bifonctionnelle. D'une part, elle conserve une affinite tres elevee pour la toxine Aah / (Kd de 2,3 10 -10 M, sensiblement equivalent a celui de l'IgG 9C2). D'autre part, elle reconnait la streptavidine et ses conjugues (streptavidine-peroxydase). Le dosage de la toxine Aahl developpe est un ELISA sandwich dans lequel la toxine est capturee de facon specifique par un anticorps monoclonal et les immuncomplexes sont ensuite detectes par l'immunoconjugue recombinant, conferant ainsi une haute specificite au dosage. Le test est rapide (90 mn), reproductible et sensible, avec une limite de detection de 0,6 ng/ml de toxine. Cette methodologie pourrait etre etendue aux deux autres toxines letales du venin du scorpion Androctonus australis hector et a celles d'autres especes. De nouvelles perspectives sont ainsi envisageables pour le diagnostic des envenimations.
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In vivo neurotoxicity of Androctonus australis hector scorpion venom: evidence that the supra-thoracic nervous system is not implicated in the clinical manifestations.
Toxicon : official journal of the International Society on Toxinology, 2001Co-Authors: O. Clot-faybesse, Herve Rochat, Christiane Devaux, Régis GuieuAbstract:The severity of scorpion stings is related to the highly active neurotoxins in the venom. In this study, rats whose supra-spinal central nervous system was deprived of its peripheral connections were experimentally poisoned by the venom of Androctonus australis hector scorpion. Clinical signs of severity were not modified when the rats had previously undergone high medullar section. These results suggest that the supra-thoracic nervous system is not implicated in the neurotoxicity manifestations of scorpion envenomation.
Pascal Mansuelle - One of the best experts on this subject based on the ideXlab platform.
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First chemical synthesis of a scorpion α-toxin affecting sodium channels: The Aah I toxin of Androctonus australis hector
Journal of Peptide Science, 2004Co-Authors: Sarrah M'barek, Pascal Mansuelle, Christiane Devaux, Ziad Fajloun, Sandrine Cestèle, Amor Mosbah, Besma Jouirou, Massimo Mantegazza, Jurphaas Van Rietschoten, Mohamed El AyebAbstract:Aah I is a 63-residue alpha-toxin isolated from the venom of the Buthidae scorpion Androctonus australis hector, which is considered to be the most dangerous species. We report here the first chemical synthesis of Aah I by the solid-phase method, using a Fmoc strategy. The synthetic toxin I (sAah I) was renatured in DMSO-Tris buffer, purified and subjected to thorough analysis and comparison with the natural toxin. The sAah I showed physico-chemical (CD spectrum, molecular mass, HPLC elution), biochemical (amino-acid composition, sequence), immunochemical and pharmacological properties similar to those of the natural toxin. The synthetic toxin was recognized by a conformation-dependent monoclonal anti-Aah I antibody, with an IC50 value close to that for the natural toxin. Following intracerebroventricular injection, the synthetic and the natural toxins were similarly lethal to mice. In voltage-clamp experiments, Na(v) 1.2 sodium channel inactivation was inhibited by the application of sAah I or of the natural toxin in a similar way. This work describes a simple protocol for the chemical synthesis of a scorpion alpha-toxin, making it possible to produce structural analogues in time.
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First chemical synthesis of a scorpion α‐toxin affecting sodium channels: The Aah I toxin of Androctonus australis hector
Journal of peptide science : an official publication of the European Peptide Society, 2004Co-Authors: Sarrah M'barek, Pascal Mansuelle, Christiane Devaux, Ziad Fajloun, Sandrine Cestèle, Amor Mosbah, Besma Jouirou, Massimo Mantegazza, Jurphaas Van Rietschoten, Mohamed El AyebAbstract:Aah I is a 63-residue alpha-toxin isolated from the venom of the Buthidae scorpion Androctonus australis hector, which is considered to be the most dangerous species. We report here the first chemical synthesis of Aah I by the solid-phase method, using a Fmoc strategy. The synthetic toxin I (sAah I) was renatured in DMSO-Tris buffer, purified and subjected to thorough analysis and comparison with the natural toxin. The sAah I showed physico-chemical (CD spectrum, molecular mass, HPLC elution), biochemical (amino-acid composition, sequence), immunochemical and pharmacological properties similar to those of the natural toxin. The synthetic toxin was recognized by a conformation-dependent monoclonal anti-Aah I antibody, with an IC50 value close to that for the natural toxin. Following intracerebroventricular injection, the synthetic and the natural toxins were similarly lethal to mice. In voltage-clamp experiments, Na(v) 1.2 sodium channel inactivation was inhibited by the application of sAah I or of the natural toxin in a similar way. This work describes a simple protocol for the chemical synthesis of a scorpion alpha-toxin, making it possible to produce structural analogues in time.
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Purification, characterization and molecular modelling of two toxin-like proteins from the Androctonus australis Hector venom.
European journal of biochemistry, 2000Co-Authors: Najet Srairi-abid, Herve Rochat, Pascal Mansuelle, Francois Sampieri, Thouraya Mejri, Habib Karoui, Mohamed El AyebAbstract:Two toxin-like proteins (AahTL1 and AahTL3) were purified from the venom of the scorpion Androctonus australis Hector (Aah). AahTL1 and AahTL3 are the first non toxic proteins cross-reacting with AahI toxins group which indicates that these proteins can be used as a model of vaccins. In order to study structure-function relationships, their complete amino-acid sequences (66 residues) were determined, by automated Edman degradation. They show more than 50% of similarity with both AahI and AahIII antimammal toxins. Three-dimensional structural models of AahTL1 and AahTL3 constructed by homology suggest that the two proteins are structurally similar to antimammal scorpion alpha-toxins specific to voltage dependent Na+ channels. The models showed also that amino-acid changes between potent Aah toxins and both AahTL1 and AahTL3 disrupt the electrostatic potential gradient at their surface preventing their interaction with the receptor, which may explain their non toxicity.
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aah vi a novel n glycosylated anti insect toxin from Androctonus australis hector scorpion venom isolation characterisation and glycan structure determination
FEBS Letters, 1999Co-Authors: Oussama Hassani, H Rochat, Damarys Loew, A Van Dorsselaer, M J Papandreou, O Sorokine, Francois Sampieri, Pascal MansuelleAbstract:Aah VI was isolated from the venom of the North African scorpion, Androctonus australis hector. It is the first glycosylated neurotoxin from scorpion venom to be described. It was not toxic to mice, when injected intracerebroventricularly at a dose of 1.2 microg per animal. However, it had typical activity in Blatella germanica cockroaches resulting in gradual paralysis and very low toxicity (LD50 = 8.5 microg/g of animal). It consists of 66 amino acid residues and is heterogeneously N-glycosylated at a single site, on asparagine 9, of the Asn-Gly-Thr sequence. The potential N-glycosylation site was deduced from automatic Edman degradation and amino acid analysis, and glycan heterogeneity was evidenced by ESMS. Determination of the N-glycan structures (dHex, Hex and HexNAc) was assessed by nanoESMS/MS with picomolar amounts of sample. Current knowledge of N-glycan structure and composition suggests that the glycan structures are derived from a common core.
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Aah VI, a novel, N‐glycosylated anti‐insect toxin from Androctonus australis hector scorpion venom: isolation, characterisation, and glycan structure determination
FEBS letters, 1999Co-Authors: Oussama Hassani, Herve Rochat, Damarys Loew, A Van Dorsselaer, M J Papandreou, O Sorokine, Francois Sampieri, Pascal MansuelleAbstract:Aah VI was isolated from the venom of the North African scorpion, Androctonus australis hector. It is the first glycosylated neurotoxin from scorpion venom to be described. It was not toxic to mice, when injected intracerebroventricularly at a dose of 1.2 microg per animal. However, it had typical activity in Blatella germanica cockroaches resulting in gradual paralysis and very low toxicity (LD50 = 8.5 microg/g of animal). It consists of 66 amino acid residues and is heterogeneously N-glycosylated at a single site, on asparagine 9, of the Asn-Gly-Thr sequence. The potential N-glycosylation site was deduced from automatic Edman degradation and amino acid analysis, and glycan heterogeneity was evidenced by ESMS. Determination of the N-glycan structures (dHex, Hex and HexNAc) was assessed by nanoESMS/MS with picomolar amounts of sample. Current knowledge of N-glycan structure and composition suggests that the glycan structures are derived from a common core.
Marzia Pisciotta - One of the best experts on this subject based on the ideXlab platform.
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Fast K(+) currents from cerebellum granular cells are completely blocked by a peptide purified from Androctonus australis Garzoni scorpion venom.
Biochimica et biophysica acta, 2000Co-Authors: Marzia Pisciotta, Fredy I.v. Coronas, G Prestipino, C Bloch, Lourival D. PossaniAbstract:A novel peptide was purified from the venom of the scorpion Androctonus australis Garzoni (abbreviated Aa1, corresponding to the systematic number alpha KTX4.4). It contains 37 amino acid residues, has a molecular mass of 3850 Da, is closely packed by three disulfide bridges and a blocked N-terminal amino acid. This peptide selectively affects the K(+) currents recorded from cerebellum granular cells. Only the fast activating and inactivating current, with a kinetics similar to I(A)-type current, is completely blocked by the addition of low micromolar concentrations (K(i) value of 150 nM) of peptide Aa1 to the external side of the cell preparation. The blockade is partially reversible in our experimental conditions. Aa1 blocks the channels in both the open and the closed states. The blockage is test potential independent and is not affected by changes in the holding potential. The kinetics of the current are not affected by the addition of Aa1 to the preparation; it means that the block is a simple 'plugging mechanism', in which a single toxin molecule finds a specific receptor site in the external vestibule of the K(+) channel and thereby occludes the outer entry to the K(+) conducting pore.
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Fast K+ currents from cerebellum granular cells are completely blocked by a peptide purified from Androctonus australis Garzoni scorpion venom
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2000Co-Authors: Marzia Pisciotta, Fredy I.v. Coronas, Gianfranco Prestipino, C Bloch, Lourival D. PossaniAbstract:AbstractA novel peptide was purified from the venom of the scorpion Androctonus australis Garzoni (abbreviated Aa1, corresponding to the systematic number alpha KTX4.4). It contains 37 amino acid residues, has a molecular mass of 3850 Da, is closely packed by three disulfide bridges and a blocked N-terminal amino acid. This peptide selectively affects the K+ currents recorded from cerebellum granular cells. Only the fast activating and inactivating current, with a kinetics similar to IA-type current, is completely blocked by the addition of low micromolar concentrations (Ki value of 150 nM) of peptide Aa1 to the external side of the cell preparation. The blockade is partially reversible in our experimental conditions. Aa1 blocks the channels in both the open and the closed states. The blockage is test potential independent and is not affected by changes in the holding potential. The kinetics of the current are not affected by the addition of Aa1 to the preparation; it means that the block is a simple ‘plugging mechanism’, in which a single toxin molecule finds a specific receptor site in the external vestibule of the K+ channel and thereby occludes the outer entry to the K+ conducting pore
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a novel toxin form the scorpion Androctonus australis blocks shaker k channels expressed in xenopus oocytes
Biochemical and Biophysical Research Communications, 1998Co-Authors: Marzia Pisciotta, Lourival D. Possani, Michela Ottolia, G PrestipinoAbstract:The Shaker B potassium channel expressed in Xenopus laevis oocytes is blocked, in a total reversible manner from the outside part, by a new toxin (Aa1) composed of 40 amino acid residues, purified from the venom of the North African scorpion Androctonus australis Garzoni. The experiments were performed with patch-clamp technique in the outside-out configuration. The half blocking concentration is approximately 4.5 microM with a 1:1 stoichiometry. The activation and inactivation kinetics of the current are not modified by the blocking mechanism. The binding affinity is not voltage dependent. These results suggest a simple bimolecular mechanism of blockade by which the toxin occludes the external vestibule of the channel and thereby inhibits the K+ ions conduction.
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The Androctonus australis garzoni scorpion venom contains toxins that selectively affect voltage-dependent K(+)-channels in cerebellum granular cells.
European biophysics journal : EBJ, 1998Co-Authors: Marzia Pisciotta, Fredy I.v. Coronas, Lourival D. Possani, Gianfranco PrestipinoAbstract:A purified peptide from Androctonus australis Garzoni venom (AaG) affects selectively a K+-current recorded from cerebellum granular cells. This current is characterized by fast activating and inactivating kinetics similar to an IA-type current. Addition of 2 µm peptide Aa1 (from Androctonus australis, toxin 1) to the external side of the channel suppressed completely and in a selective manner the IA-type current, with an IC50 value of 130 nm, whereas in the same conditions, the other potassium current, identified as delayed rectifier (Id), was not affected. Additionally, we show that another partially purified peptide (III-12) from the same venom was able to block reversibly both K+-currents.
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the Androctonus australis garzoni scorpion venom contains toxins that selectively affect voltage dependent k channels in cerebellum granular cells
European Biophysics Journal, 1998Co-Authors: Marzia Pisciotta, Fredy I.v. Coronas, Lourival D. Possani, Gianfranco PrestipinoAbstract:A purified peptide from Androctonus australis Garzoni venom (AaG) affects selectively a K+-current recorded from cerebellum granular cells. This current is characterized by fast activating and inactivating kinetics similar to an IA-type current. Addition of 2 µm peptide Aa1 (from Androctonus australis, toxin 1) to the external side of the channel suppressed completely and in a selective manner the IA-type current, with an IC50 value of 130 nm, whereas in the same conditions, the other potassium current, identified as delayed rectifier (Id), was not affected. Additionally, we show that another partially purified peptide (III-12) from the same venom was able to block reversibly both K+-currents.