Maurotoxin, a four disulfide bridge toxin from Scorpio maurus venom: purification, structure and action on potassium channels

FEBS Letters

El Ayeb, M¹  Sampieri, F³  Oughideni, R³  Rochat, H³  Kharrat, R¹  Crest, M²  Van Rietschoten, J³  Mansuelle, P³  Martin-Eauclaire, M.F³ 

[1] Laboratoire des Venins et Toxines, Institut Pasteur de Tunis, 13 Place Pasteur, B.P. 74, 1002 Tunis-Bélvédère, Tunisia;Laboratoire de Neurobiologie, CNRS-UPR 9024, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France;UMR 6560, Université de la Méditerranée CNRS, Laboratoire de Biochimie, Ingénierie des Protéines, IFR Jean Roche, Faculté de Médecine Nord, Bd. P. Dramard, 13916 Marseille Cedex 20, France

关键词: Scorpion toxin;    Potassium channel;   

DOI  :  10.1016/S0014-5793(97)00285-8

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

A new toxin acting on K⁺ channels, maurotoxin (MTX), has been purified to homogeneity from the venom of the chactoid scorpion Scorpio maurus. MTX is a basic single chain 34 amino acid residue polypeptide, amidated at its C terminal, and crosslinked by four disulfide bridges. It shows 29–68% sequence identity with other K⁺ channel toxins, and presents an original disulfide pattern, the last two half-cystine residues (31–34) being connected. Although the first three disulfide bonds have not been defined experimentally, modelling based on the structure of charybdotoxin favored two combinations out of six, one of which has two bridges (3–24 and 9–29) in common with the general motif of scorpion toxins. The last bridge would connect residues 13 and 19. MTX inhibits the binding to rat brain synaptosomal membranes of both [¹²⁵I]apamin, a SK_Ca channel blocker (IC₅₀ 5 nM), and [¹²⁵I]kaliotoxin, a Kv channel blocker (IC₅₀ 30 pM). MTX blocks the Kv1.1, Kv1.2 and Kv1.3 currents expressed in Xenopus oocytes with IC₅₀ of 45, 0.8 and 180 nM, respectively. MTX represents a member of a new class of short toxins with 4 disulfide bridges, active on voltage-dependent K⁺ channel and also competing with apamin for binding to its receptor.

【 授权许可】

Unknown