P59868 · CAIMP_PANIM

Function

function

This toxin affects the activity of ryanodine receptors 1, 2 and 3 (RyR1, RyR2 and RyR3) (PubMed:11867448, PubMed:1334561, PubMed:9565405).
At lower concentrations the toxin increases full openings of the RyRs, and at higher concentrations it inhibits full openings and induces openings to subconductance levels (30% of the full conductance state) and reduces the number of full conductance openings (PubMed:27114612, PubMed:9565405).
The different actions may be attributed to the toxins binding at different sites on the RyRs, with binding at a high-affinity site mediating the increase in full openings and the induction of subconductance states evoked upon binding to a lower-affinity site (PubMed:14699105).
Furthermore, it triggers calcium release from sarcoplasmic vesicles (11.7 nM are enough to induce a sharp release, and 70% of the total calcium is released after toxin (100 nM) addition) probably by acting as a cell-penetrating peptide (CPP) (PubMed:1334561, PubMed:27114612).
In addition, it has been shown to dose-dependently stimulate ryanodine binding to RyR1 (EC50=8.7 nM) (PubMed:27114612).
It also augments the bell-shaped calcium-[3H]ryanodine binding curve that is maximal at about 10 uM calcium concentration (PubMed:27114612).
It binds a different site as ryanodine (PubMed:9565405).
It acts synergistically with caffeine (By similarity).
In vivo, intracerebroventricular injection into mice induces neurotoxic symptoms, followed by death (By similarity).

Features

Showing features for site.

TypeIDPosition(s)Description
Site6Important for stimulation of [3H]ryanodine binding to RYR1
Site7Essential for stimulation of [3H]ryanodine binding to RYR1
Site11Important for stimulation of [3H]ryanodine binding to RYR1
Site30Important for stimulation of [3H]ryanodine binding to RYR1
Site31Essential for stimulation of [3H]ryanodine binding to RYR1
Site33Essential for stimulation of [3H]ryanodine binding to RYR1

GO annotations

AspectTerm
Cellular Componentextracellular region
Molecular Functioncalcium channel inhibitor activity
Molecular Functiontoxin activity

Keywords

Names & Taxonomy

Protein names

  • Recommended name
    Imperacalcin
  • Short names
    IpCa
  • Alternative names
    • Imperatoxin activator
    • Imperatoxin-A
      (IpTxa
      )

Organism names

  • Taxonomic identifier
  • Taxonomic lineage
    Eukaryota > Metazoa > Ecdysozoa > Arthropoda > Chelicerata > Arachnida > Scorpiones > Iurida > Scorpionoidea > Scorpionidae > Pandininae > Pandinus

Accessions

  • Primary accession
    P59868

Subcellular Location

Keywords

Phenotypes & Variants

Features

Showing features for mutagenesis.

TypeIDPosition(s)Description
Mutagenesis11.18-fold decrease of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis22.33-fold increase of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis3Linear IpCa; Loss of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis41.93-fold decrease of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis51.43-fold decrease of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis620.72-fold decrease of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis797.51-fold decrease of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis84.60-fold decrease of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis925.62-fold decrease of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis10Linear IpCa; Loss of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis116.83-fold decrease of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis133.08-fold increase of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis141.14-fold decrease of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis152.73-fold increase of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis16Linear IpCa; Loss of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis17Linear IpCa; Loss of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis181.16-fold decrease of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis194.96-fold decrease of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis2016.91-fold decrease of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis21Linear IpCa; Loss of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis2269.92-fold decrease of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis23418.48-fold decrease of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis24Loss of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis2523.96-fold decrease of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis2611.52-fold decrease of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis2720.09-fold decrease of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis292.35-fold increase of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis3021.69-fold decrease of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis31Loss of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis32Linear IpCa; Loss of stimulation of [3H]ryanodine binding to RYR1.
Mutagenesis33Loss of stimulation of [3H]ryanodine binding to RYR1.

PTM/Processing

Features

Showing features for peptide, disulfide bond.

TypeIDPosition(s)Description
PeptidePRO_00000449491-33Imperacalcin
Disulfide bond3↔17
Disulfide bond10↔21
Disulfide bond16↔32

Keywords

Expression

Tissue specificity

Expressed by the venom gland.

Family & Domains

Features

Showing features for region.

TypeIDPosition(s)Description
Region8-9Important for stimulation of [3H]ryanodine binding to RYR1
Region19-20Important for stimulation of [3H]ryanodine binding to RYR1
Region22-24Essential for stimulation of [3H]ryanodine binding to RYR1
Region25-27Important for stimulation of [3H]ryanodine binding to RYR1

Domain

The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin.

Sequence similarities

Belongs to the scorpion calcin family.

Keywords

Family and domain databases

Sequence

  • Sequence status
    Complete
  • Length
    33
  • Mass (Da)
    3,764
  • Last updated
    2003-09-26 v1
  • Checksum
    D0DF8EFFFE294537
GDCLPHLKRCKADNDCCGKKCKRRGTNAEKRCR

Keywords

Similar Proteins

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