Scyllatoxin

Scyllatoxin
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Scyllatoxin is a toxin from the scorpion Leiurus quinquestriatus hebraeus, which blocks small-conductance Ca2+-activated K+ channels.

1 Source
2 Chemistry
3 Target
4 Mode of action
5 Toxicity
6 Treatment
7 References
8 External links
- 8.1 Links of articles to Pubmed

Source

Scyllatoxin (also leiurotoxin I) is one of the components of the venom of the Israeli scorpion ‘Leiurus quinquestriatus hebraeus’. It consists of only 0.02% of the total protein in crude venom.¹

Chemistry

Leiurotoxin I is a 31-residue toxin, with a helix and a short antiparallel β-sheet. This toxin is stabilized by disulfide bonds: Cys8-Cys26 and Cys12-Cys28 is bound to the β-sheet, Cys3-Cys21 is bound to an N-terminal segment preceding the helix. Leiurotoxin adopts the ά/β motif.¹ Especially the positively charged residues (Arg6 and Arg13, which are located in the ά helix) are important for the expression of toxin biological activities² and for its receptor affinity.³

Target

Scyllatoxin is a blocker of small-conductance Ca2+– activated K+ channels at 10-13 – 10-11 M concentrations in various cell types.¹ This toxin shows similarity in its physiological activity and binding specificity to apamin,¹ but both toxins show no structural similarity.⁴

Mode of action

Scyllatoxin blocks the slow after-hyperpolarization that follows an action potential in some nerve cells.¹

Toxicity

Scyllatoxin induces spontaneous contractions in guinea pig taenia coli muscle cells that have been relaxed with epinephrine.⁵

Treatment

Please help improve this section by expanding it. Further information might be found on the talk page or at requests for expansion. (June 2008)

References

^ ^a ^b ^c ^d ^e Zhu Q., Liang S., Martin L., Gasparini S., Me´nez A., Vita C..Role of Disulfide Bonds in Folding and Activity of Leiurotoxin I: Just Two Disulfides Suffice. Biochemistry 2002; 41: 11488-11494.
^ Sabatier J.M., Lecomte C., Mabrouk K., Darbon H., Oughideni R., Canarelli S., Rochat H., Martin-Eauclaire M.F., Van Rietschoten J. Synthesis and Characterization of Leiurotoxin I Analogs Lacking One Disulfide Bridge: Evidence That Disulfide Pairing 3-21 Is Not Required for Full Toxin Activity. Biochemistry 1996; 35: 10641-10647.
^ Buisine E. Wieruszeski J.M., Lippens G., Wouters D., Tartar A., Sautiere P. Characterization of a new family of toxin-like peptides from the venom of the scorpion Leiurus quinquestriatus hebraeus. 1H-NMR structure of leiuropeptide II. J. Pept. Res. 1997;49:545-55
^ Chicchi G.G., Gimenez-Gallego G., Ber E. Garcia M.L. Winquist R. Cascieri M.A. Purification and characterization of a unique, potent inhibitor of apamin binding from Leiurus quinquestriatus hebraeus venom. J. Biol. Chem. 1988; 21: 10192-7.
^ Auguste P., Hugues M., Mourre C., Moinier D., Tartar A., Lazdunski M.. Scyllatoxin, a Blocker of Ca2+-Activated K+ Channels: Structure-Function Relationships and Brain Localization of the Binding Sites. Biochemistry 1992; 31:648-654.