Modulates P-type voltage-gated calcium channels (Cav2.1/CACNA1A) in rat cerebellar Purkinje cells and hippocampal CA1-CA3 neurons. At saturating concentrations (>10 nM) the toxin decelerates activation kinetics and slightly increases peak amplitude without affecting deactivation kinetics. Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. Contains 4 disulfide bonds. Belongs to the neurotoxin (omega-lctx) family.