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BotIT6: a potent depressant insect toxin from Buthus occitanus tunetanus venom.

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Mejri, Thouraya | Borchani, Lamia | Srairi-Abid, Najet | Benkhalifa, Rym | Cestele, Sandrine | Regaya, Imed | Karoui, Habib | Pelhate, Marcel | Rochat, Hervé | El Ayeb, Mohamed

Edité par CCSD ; Elsevier -

International audience. A new depressant insect toxin Buthus occitanus tunetanus insect-toxin 6 (BotIT6) was purified by high-performance liquid chromatography from Buthus occitanus tunetanus (Bot) venom. BotIT6 is very active against Blatella germanica (LD50=10ng/100mg body mass) thus being one of the most potent anti-insect toxin so far characterised. When compared to other insect toxin sequences, BotIT6 present high similarities with depressant insect toxins with an additional arginine residue at the C-terminus and a methionine at position 27. The calculated net charge of BotIT6 is positive (+3) whereas it is negative for classical depressant toxins: this might be associated with its high toxicity. Voltage current clump studies show that BotIT6 is not a very potent depressant insect toxin despite its high toxicity in vivo. BotIT6 is able to fully inhibit the specific binding of 125I AaHIT and 125I-BotIT2 on Periplaneta americana synaptosomal membrane vesicles with high affinities. Despite its higher toxicity BotIT6 is a weaker competitor with 125I AaHIT and 125I BotIT2 as compared to the other beta toxins.Altogether, these results may suggest that BotIT6 probably defines a novel sub-group of depressant anti-insect toxins for which the receptor site can be overlapping, but not identical to that for classical depressant insect toxins.

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