This toxin affects the activity of ryanodine receptors 1, 2 and 3 (RyR1, RyR2 and RyR3) (PubMed:1334561, PubMed:9565405, PubMed:11867448). 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:9565405, PubMed:27114612). 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 (EC(50)=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). Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. Belongs to the scorpion calcin family.