Allosteric inhibitor of alpha-1B adrenergic receptors (ADRA1B). Binds to an allosteric modulatory site on transmembrane helix 6 and 7 at the base of extracellular loop 3 of ADRA1B (PubMed:23184947). Also weekly inhibits alpha-1A (ADRA1A) and alpha-1D (ADRA1D) adrenergic receptors in a competive manner (PubMed:15194691). Potently inhibits contractions of vas deferens, spleen and aorta in response to noradrenaline (PubMed:15680270). May also inhibits nicotinic acetylcholine receptors with a possible distinct nAChR binding mode from other alpha-conotoxins, due to a different three residue motif (lacks the Ser-Xaa-Pro motif) (By similarity). Expressed by the venom duct. The cysteine framework is I (CC-C-C). Alpha4/7 pattern. Has no effect on alpha-2 adrenergic receptors (ADRA2) (PubMed:11528421, PubMed:12824165). Belongs to the conotoxin A superfamily. Extended N-terminus.