Toxin that inhibits presynaptic voltage-gated calcium channel (Cav) in Drosophila nerve terminals, most likely through specific block of the Cav2 channel (known as Dmca1A). Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. Contains 5 disulfide bonds. Acylation by palmitate is required for biological activity. Belongs to the neurotoxin 02 (plectoxin) family. 02 (plectoxin) subfamily.