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. 1992 Dec 15;89(24):12185–12189. doi: 10.1073/pnas.89.24.12185

Scorpion toxins targeted against the sarcoplasmic reticulum Ca(2+)-release channel of skeletal and cardiac muscle.

H H Valdivia 1, M S Kirby 1, W J Lederer 1, R Coronado 1
PMCID: PMC50723  PMID: 1334561

Abstract

We report the purification of two peptides, called "imperatoxin inhibitor" and "imperatoxin activator," from the venom of the scorpion Pandinus imperator targeted against ryanodine receptor Ca(2+)-release channels. Imperatoxin inhibitor has a M(r) of approximately 10,500, inhibits [3H]ryanodine binding to skeletal and cardiac sarcoplasmic reticulum with an ED50 of approximately 10 nM, and blocks openings of skeletal and cardiac Ca(2+)-release channels incorporated into planar bilayers. In whole-cell recordings of cardiac myocytes, imperatoxin inhibitor decreased twitch amplitude and intracellular Ca2+ transients, suggesting a selective blockade of Ca2+ release from the sarcoplasmic reticulum. Imperatoxin activator has a M(r) of approximately 8700, stimulates [3H]ryanodine binding in skeletal but not cardiac sarcoplasmic reticulum with an ED50 of approximately 6 nM, and activates skeletal but not cardiac Ca(2+)-release channels. These ligands may serve to selectively "turn on" or "turn off" ryanodine receptors in fragmented systems and whole cells.

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Selected References

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