Alpha-conotoxin OmIA

UniProtKB accession:  P0C1R7

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UniProtKB description:  Alpha-conotoxins act on postsynaptic membranes, they bind to the nicotinic acetylcholine receptors (nAChR) and thus inhibit them. This toxin blocks alpha-3-beta-2/CHRNA3-CHRNB2 (IC(50)=11 nM), alpha-7/CHRNA7 (IC(50)=27.1-59 nM (rat)/ 290 nM (human)), alpha-3-beta-4/CHRNA3-CHRNB4 (IC(50)=160 nM), and alpha-6/alpha-3-beta-2-beta-3 (CHRNA6/CHRNA3-CHRNB2-CHRNB3) (IC(50)=201 nM) nAChR (PubMed:16803900, PubMed:30025921, PubMed:34955864). In the OmIA-AChBP complex, this toxin occupies all five binding pockets located between two adjacent subunits of the homopentamer (PubMed:34955864). Despite a competitive binding mode observed in the co-crystal structure, it displays functional insurmountable antagonism at alpha-7 and alpha-3-beta-4 nAChRs (PubMed:34955864). It also shows biphasic-inhibition at alpha-7 nAChRs in the presence of the positive allosteric modulator PNU120596, with a preference for the high-affinity binding site following prolonged exposure (PubMed:34955864).