A novel short neurotoxin,cobrotoxin c,from monocellate cobra (Naja kaouthia) venom: isolation and purification,primary and secondary structure determination,and tertiary structure modeling |
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Authors: | Meng Qing-Xiong Wang Wan-Yu Lu Qiu-Min Jin Yang Wei Ji-Fu Zhu Shao-Wen Xiong Yu-Liang |
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Institution: | Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, PR China. |
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Abstract: | A novel short neurotoxin, cobrotoxin c (CBT C) was isolated from the venom of monocellate cobra (Naja kaouthia) using a combination of ion-exchange chromatography and FPLC. Its primary structure was determined by Edman degradation. CBT C is composed of 61 amino acid residues. It differs from cobrotoxin b (CBT B) by only two amino acid substitutions, Thr/Ala11 and Arg/Thr56, which are not located on the functionally important regions by sequence similarity. However, the LD50 is 0.08 mg/g to mice, i.e. approximately five-fold higher than for CBT B. Strikingly, a structure-function relationship analysis suggests the existence of a functionally important domain on the outside of Loop III of CBT C. The functionally important basic residues on the outside of Loop III might have a pairwise interaction with alpha subunit, instead of gamma or delta subunits of the nicotinic acetylcholine receptor (nAChR). |
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Keywords: | Snake venom Short neurotoxin Cobrotoxin c Amino acid sequence Three-finger proteins Lethal toxicity Comparative structure modeling Functional domain |
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