Acts as a co-agonist with PNU (an alpha-7 nAChR-selective allosteric modulator) at the endogenous alpha-7/CHRNA7 nicotinic acetylcholine receptors (nAChR) when tested in human SH-SY5Y neuroblastoma cells. Is the third alpha-conotoxin that acts as an agonist (after alpha-conotoxin SrIA/SrIB). Also acts as an antagonist at human alpha-7 nAChRs heterologously expressed in Xenopus oocytes (PubMed:24351107). Has possibly a distinct nAChR binding mode from other alpha-conotoxins, due to a different three residue motif (lacks the Ser-Xaa-Pro motif) (By similarity). Acts as a weak partial agonist at alpha-7/CHRNA7 nicotinic acetylcholine receptors (nAChR) when tested in human SH-SY5Y neuroblastoma cells (PubMed:24351107). Has possibly a 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. Two 4-hydroxyprolines have been detected by MS but the assignment of which of the three prolines is modified is uncertain (PubMed:23152539, and PubMed:24351107). Neither MrIC, Mr1.7b, nor Mr1.7a inhibit alpha-7/CHRNA7, alpha-3-beta-2/CHRNA3-CHRNB2 and alpha-3-beta-4/CHRNA3-CHRNB4 nAChRs endogenously expressed in human SH-SY5Y neuroblastoma cells. MrIC does not activate alpha-3-beta-2/CHRNA3-CHRNB2 and alpha-3-beta-4/CHRNA3-CHRNB4 endogenously expressed in human SH-SY5Y neuroblastoma cells. Mr1.7b does not activate alpha-7 endogenously expressed in human SH-SY5Y neuroblastoma cells (PubMed:24351107). Belongs to the conotoxin A superfamily. The cDNA sequence of this peptide has been submitted (EMBL entry JF460791) and described in PubMed:22781954 under the name Mr1.8.