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Imperatoxin A


A Ryanodine Receptor Modulator

Cat #: STI-333
Alternative Name IpTxa
Lyophilized Powder yes
Origin Synthetic peptide
MW: 3758 Da
Purity: >98% (HPLC)
Form Lyophilized powder.
Effective concentration 10-300 nM.
Modifications Disulfide bonds between Cys3-Cys17, Cys10-Cys21 and Cys16-Cys32.
Molecular formula C148H254N58O45S6.
CAS No.: 172451-37-5
Activity Imperatoxin A is a strong agonist of ryanodine receptor channels (RyR)1. Induces voltage- and concentration-dependent subconductance states in both skeletal (RYR1 and RYR3) and cardiac (RYR2) ryanodine receptors by binding to a single, cytosolic accessible site different from the ryanodine binding site. The activating effect is dose-dependent (ED50=10 nM), with fast onset and found fully reversible2.
  1. Valdivia, H.H. et al. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 12185.
  2. El-Hayek, R. et al. (1995) J. Biol. Chem. 270, 28696.
Shipping and storage Shipped at room temperature. Product as supplied can be stored intact at room temperature for several weeks. For longer periods, it should be stored at -20°C.
Solubility Water or 0.9% NaCl solution. Centrifuge all product preparations before use (10000 x g 5 min).
Storage of solutions Store at 4°C for up to 1 week. For longer periods, small aliquots should be stored at -20°C. Avoid multiple freezing and thawing.
References - Scientific background
  1. Valdivia, H.H. et al. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 12185.
  2. El-Hayek, R. et al. (1995) J. Biol. Chem. 270, 28696.
  3. Zamudio, F. Z. et al.  (1997) FEBS Lett. 405, 385.
  4. Gurrola G.B. et al. (1999) J. Biol. Chem274, 7879.
Scientific background

Imperatoxin A (IpTxa) is a 33 amino acid natural peptidyl toxin isolated from the venom of scorpion Pandinus imperator. IpTxa interacts specifically and activates the sarcoplasmic reticulum Ca2+-release channel of skeletal and cardiac muscle (ryanodine receptor 1 and 2). It reversibly enhances binding of ryanodine to the receptors. The activating effect of IpTxa on skeletal ryanodine receptor is Ca2+-dependent, synergized by caffeine, and independent of other modulators of RyRs1-3.

IpTxa increased the open probability of rabbit skeletal muscle RyRs by increasing the frequency of open events and decreasing the duration of the closed lifetimes.2

IpTxa displays structural homology with an activating segment of the a1 subunit of the skeletal dihydropyridine receptor (II-III loop, segment Glu666-Leu690) which is putatively the native activator of ryanodine receptor. IpTxa and the segment Glu666-Leu690 activate RyRs in a similar manner and appear to compete for a common binding site on the ryanodine channel protein4. This suggest a common mechanism of IpTxa and dihydropyridine receptor for modulation of RyR4.

Target Ryanodine receptors
Peptide Content: 100%
Last update: 02/01/2022

Imperatoxin-A (#STI-333) is a highly pure, synthetic, and biologically active peptide toxin.

For research purposes only, not for human use



Product citations
  1. Nesuashvili, C. et al. (2013) Mol. Pharmacol. 83, 1007.
  2. Diaz-Sylvester, P.L. and Copello, J.A. (2009) PLoS ONE 4, e8315.
  3. Porta, M. et al. (2008) Biochim. Biophys. Acta 1778, 2469.


Scientific Background

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