Cell penetrating peptide (CPP) that increases intracellular calcium release through the activation of nuclear inositol 1,4,5-trisphosphate receptors (ITPR) of cardiomyocytes, thereby causing an increase in the contraction frequency of these cells (PubMed:30282983). In vivo, this toxin is not lethal to mice, hovewer anti-CPP serum reduces venom lethality, suggesting that this toxin is lethal when it acts in synergy with other venom components (PubMed:30282983). Secreted in the venom and directed to the intranuclear region of cardiomyocytes (PubMed:30282983). Expressed by the venom gland. In intravenously injected mice, the labeled toxin has preference for heart, liver and lungs. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. The peptide(14-39) may have biotechnological applications as a drug delivery system targeting cancer cells, since it lacks pharmacological activity of the wild-type toxin and has selective internalization properties in specific cell lines. It is directed to the nucleus of six neoplastic cell lines (SK-MEL-188, HEP G2, Caco-2, MDA-MB-231, A549 and DU 145), as well as in rat cardiomyocytes, and rat heptocytes. However, it is unable to cross the cell membrane of six normal immortalized cell lines (HUV-EC-C, HFF-1, MCR-5, HEK-293, BHK-21 and MDCK). Belongs to the scorpion calcin-like family.