Scyllatoxin

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

Contents

[edit] 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]

[edit] 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 activities[2] and for its receptor affinity.[3]

[edit] 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]

[edit] Mode of action

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

[edit] Toxicity

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

[edit] Treatment

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[edit] References

  1. ^ 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.
  2. ^ 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.
  3. ^ 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
  4. ^ 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.
  5. ^ 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.

[edit] External links

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