Alpha-conotoxins act on postsynaptic membranes, they bind to the nicotinic acetylcholine receptors (nAChR) and thus inhibit them. This peptide has been experimentally synthesized as AusIA-globular and AusIA-ribbon. Both forms are active on chicken alpha-7/CHRNA7 nAChR with similar potency (micromolar range). Expressed by the venom duct. The cysteine framework is I (CC-C-C). Alpha5/5 pattern. The equipotent ability to inhibit alpha-7/CHRNA7 nAChR subunit by both the globular and ribbon toxin arise mainly from the insertion of an additional residue in the first loop and partly from residues in the termini. Two isomers (with different disulfide connectivity) have been synthesized (AusIA-globular (C1-C3, C2-C4) and AusIA-ribbon (C1-C4, C2-C3)). Only AusIA-globular contains the cysteine connectivity described as typical for native alpha-conotoxins. However, AusIA-ribbon is more potent than AusIA-globular, suggesting that another disulfide connectivity may exist in nature. Both isomers adopt very flexible structures without having a unique folded structure, lacking any stable alpha-helical and/or beta-turn units. Neither AusIA-globular nor AusIA-ribbon shows effect on muscle nAChRs alpha-1-beta-1-epsilon-delta/CHRNA1-CHRNB1-CHRNE-CHRND (adult subtype) and alpha-1-beta-1-gamma-delta/CHRNA1-CHRNB1-CHRNG-CHRND (fetal subtype) and on neuronal nAChRs alpha-3-beta-4/CHRNA3-CHRNB4, alpha-4-beta-4/CHRNA4-CHRNB4 and alpha-4-beta-2/CHRNA4-CHRNB2. Belongs to the conotoxin A superfamily.