Alpha-conotoxins act on postsynaptic membranes, they bind to the nicotinic acetylcholine receptors (nAChR) and thus inhibit them. This toxin inhibits rat alpha-3-beta-2/CHRNA3-CHRNB2 (IC(50)=3.5 nM), rat alpha-7/CHRNA7 (IC(50)=392 nM) nAChR, and the L.stagnalis soluble acetylcholine receptor (all tested without hydroxyproline). Expressed by the venom duct (PubMed:17660751, PubMed:23031820). Tx1a that containing 1 or 2 non-hydroxylated prolines are mostly present in part 5 of the venom duct (distal part near the pharynx), whereas tx1a-OO (with 2 hydroxyprolines) is mostly present in part 4 of the venom duct (follewed by part 3) (PubMed:23031820). The cysteine framework is I (CC-C-C). Alpha4/7 pattern. Exists in 4 different forms, depending on hydroxylations. Tx1a-PP does not contain hydroxyproline, tx1a-OP has one hydroxyproline at position 45, tx1a-PO has one hydroxyproline at position 46, and tx1a-PP has two hydroxyprolines at positions 45 and 46. Monoisotopic mass. Shows no inhibition on alpha-4-beta-2/CHRNA4-CHRNB2 and on alpha-1-beta-1-delta-epsilon/CHRNA1-CHRNB1-CHRND-CHRNE up to 10 uM. The toxin with a different disulfide pairing [C1-C4; C2-C3] shows an important loss of activity on L.stagnalis soluble acetylcholine receptor and a complete loss of activity on alpha-7/CHRNA7 nAChR, respectively. Belongs to the conotoxin A superfamily.