This toxin stabilizes ryanodine receptor 1 (RyR1) opening in a long-lasting subconductance state (20% and 38% of the full conductance state have been found) (PubMed:17291197, PubMed:27114612). It promotes an increase in the opening probability at intermediate concentration (PubMed:17291197). Furthermore, it triggers calcium release from sarcoplasmic vesicles (68 nM are enough to induce a sharp release, and 45% of the total calcium is released after toxin (100 nM) addition) probably by acting as a cell-penetrating peptide (CPP) (PubMed:17291197, PubMed:27114612). In addition, it has been shown to dose-dependently stimulate ryanodine binding to RyR1 (EC(50)=6.9-71 nM) (PubMed:17291197, 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 (By similarity). It acts synergistically with caffeine (By similarity). In vivo, intracerebroventricular injection into mice induces neurotoxic symptoms, followed by death (PubMed:17291197). Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. LD(50) is 15 ug/kg by intracerebroventricular injection into mice. Belongs to the scorpion calcin family.