Scyllatoxin

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

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.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. ]

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.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. ] Especially the positively charged residues (Arg6 and Arg13, which are located in the ά helix) are important for the expression of toxin biological activitiesSabatier 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.] and for its receptor affinity.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 ]

Target

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

Mode of action

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

Toxicity

Scyllatoxin induces spontaneous contractions in guinea pig taenia coli muscle cells that havebeen relaxed with epinephrine. 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.]

Treatment

References

External links

Links of articles to Pubmed

*http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=12234192&query_hl=3&itool=pubmed_docsum
*http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=8718853&query_hl=6&itool=pubmed_docsum
*http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?CMD=Search&DB=pubmed
*http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=1731919&query_hl=13&itool=pubmed_docsum