Scorpion calcine (IPR012632)

Short name: Scorpion_calcine

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