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acetylcholine binding protein (AChBP) This family contains acetylcholine binding protein (AChBP) which is a soluble extracellular domain homolog secreted by protostomia, and has been widely recognized as a surrogate for the ligand binding domain of nicotinic acetylcholine receptors (nAChRs). AChBP forms a pentameric structure where the interfaces between the subunits provide an acetylcholine (ACh) binding pocket homologous to the binding pocket of nAChRs. Thus far, AChBPs have been characterized only in aquatic mollusks, which have shown low sensitivity to neonicotinoids, the insecticides targeting insect nAChRs. Lymnaea stagnalis acetylcholine binding protein (Ls-AChBP) which has been found in glial cells as a water-soluble protein modulating synaptic ACh concentration has its the binding pocket show better resemblance as it contains all the five aromatic residues fully conserved in nAChR. Five AChBP subunits have been characterized in Pardosa pseudoannulata, a predator enemy against rice insect pests, and share higher sequence similarities with nAChR subunits of both insects and mammals compared with mollusk AChBP subunits.
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