PROSITE documentation PDOC60028
Scorpion calcine family signature


Toxins of the scorpion calcine family bind directly to ryanodine receptors (RyRs), intracellular channel targets of the endoplasmic reticulum, and induce long lasting channel openings in a mode of smaller conductance. They have the ability to translocate into cells by crossing the plasma membrane [1,2,3].

Toxins of scorpion calcine family are highly basic 33-amino acid peptides that present three disulfide bridges (C1-C4, C2-C5, and C3-C6) and fold along a knottin or inhibitor cystine knot motif (see <PDOC60004>) [1,2,3] [E1]. Their three dimensional structure consists of a compact disulfide-bonded core from which emerge loops and the N-terminus. The main element of regular secondary structure is a double-stranded antiparallel β-sheet. A third peripheral extended strand is almost perpendicular to the double-stranded antiparallel β-sheet [2,4]. Scorpion calcine mimic the activating segment of the dihydropyridine receptor II-III loop, which interacts with a region of the ryanodine receptor (see <PDB:1C6W>) [1,2,5].

This family includes:

  • Imperatoxin-A (IpTx A) from Pandinus imperator (Emperor scorpion).
  • Opicalcin-1 and -2 from Opistophthalmus carinatus (African yellow leg scorpion).
  • Maurocalcin (MCa) from Scorpio maurus palmatus (Chactoid scorpion).

We have developed a pattern that contains six conserved cysteines with a C-C-CC-C-C cysteine arrangement.

Expert(s) to contact by email:

Ramakumar S.

Last update:

February 2006 / First entry.


Technical section

PROSITE method (with tools and information) covered by this documentation:

SCORPION_CALCINE, PS60028; Scorpion calcine family signature  (PATTERN)


1AuthorsGurrola G.B. Arevalo C. Sreekumar R. Lokuta A.J. Walker J.W. Valdivia H.H.
TitleActivation of ryanodine receptors by imperatoxin A and a peptide segment of the II-III loop of the dihydropyridine receptor.
SourceJ. Biol. Chem. 274:7879-7886(1999).
PubMed ID10075681

2AuthorsFajloun Z. Kharrat R. Chen L. Lecomte C. Di Luccio E. Bichet D. El Ayeb M. Rochat H. Allen P.D. Pessah I.N. De Waard M. Sabatier J.M.
TitleChemical synthesis and characterization of maurocalcine, a scorpion toxin that activates Ca(2+) release channel/ryanodine receptors.
SourceFEBS. Lett. 469:179-185(2000).
PubMed ID10713267

3AuthorsEsteve E. Mabrouk K. Dupuis A. Smida-Rezgui S. Altafaj X. Grunwald D. Platel J.-C. Andreotti N. Marty I. Sabatier J.-M. Ronjat M. De Waard M.
TitleTransduction of the scorpion toxin maurocalcine into cells. Evidence that the toxin crosses the plasma membrane.
SourceJ. Biol. Chem. 280:12833-12839(2005).
PubMed ID15653689

4AuthorsMosbah A. Kharrat R. Fajloun Z. Renisio J.-G. Blanc E. Sabatier J.-M. El Ayeb M. Darbon H.
TitleA new fold in the scorpion toxin family, associated with an activity on a ryanodine-sensitive calcium channel.
SourceProteins 40:436-442(2000).
PubMed ID10861934

5AuthorsGreen D. Pace S. Curtis S.M. Sakowska M. Lamb G.D. Dulhunty A.F. Casarotto M.G.
TitleThe three-dimensional structural surface of two beta-sheet scorpion toxins mimics that of an alpha-helical dihydropyridine receptor segment.
SourceBiochem. J. 370:517-527(2003).
PubMed ID12429019


PROSITE is copyrighted by the SIB Swiss Institute of Bioinformatics and distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives (CC BY-NC-ND 4.0) License, see prosite_license.html.


View entry in original PROSITE document format
View entry in raw text format (no links)