Scorpion calcine (IPR012632)

Short name: Scorpion_calcine

Overlapping homologous superfamilies


Family relationships



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 [PMID: 10075681, PMID: 10713267, PMID: 15653689].

Toxins of scorpion calcine family are highly basic 33-amino acid peptides that present three disulphide bridges (C1-C4, C2-C5, and C3-C6) and fold along a knottin or inhibitor cystine knot motif ( [PMID: 10075681, PMID: 10713267, PMID: 15653689]. Their three dimensional structure consists of a compact disulphide-bonded core from which emerge loops and the N terminus. The main element of regular secondary structure is a double-stranded antiparallel beta-sheet. A third peripheral extended strand is almost perpendicular to the double-stranded antiparallel beta-sheet [PMID: 10713267, PMID: 10861934]. Scorpion calcine mimic the activating segment of the dihydropyridine receptor II-III loop, which interacts with a region of the ryanodine receptor [PMID: 10075681, PMID: 10713267, PMID: 12429019].

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).

GO terms

Biological Process

GO:0009405 pathogenesis

Molecular Function

GO:0019855 calcium channel inhibitor activity

Cellular Component

GO:0005576 extracellular region

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE patterns