Intracranial injection into mice causes scratching and hyperactivity. Expressed by the venom duct. Is present in all duct parts with a highest content in part 2 (proximal of the venom bulb) and then decreases in concentration toward the end of the duct. The cysteine framework is III (CC-C-C-CC). Classified in the M-1 branch, since 1 residue stands between the fourth and the fifth cysteine residues. Two short peptides are produced from this precursor; Conotoxin tx3a-b is amidated at Cys-69 (but has no bromotryptophan), whereas conotoxin tx3a-a has an unmodified Gly-70 and a bromotryptophan (PubMed:15924437, PubMed:17042781, PubMed:19380747, PubMed:22709442). Two elongated peptides are also produced; Conotoxin elongated-tx3a-b is amidated at Cys-69 (but has no bromotryptophan), whereas conotoxin elongated tx3a-a has an unmodified Gly-70 (but has no bromotryptophan) (PubMed:22709442). With amidation at Cys-69. Belongs to the conotoxin M superfamily.