Determining the structure of the ligand-binding domain of the nicotinic
acetylcholine receptor (nAChR) has been a long standing goal in the design of
selective drugs useful in implicated diseases for this prevalent receptor
family. Acetylcholine-binding proteins have proven to be valuable surrogates
with structural similarity and sequence identity to the extracellular domain of
the nicotinic receptor, yet these soluble proteins have their unique features
and do not serve as exact replicates of the nAChRs of interest. Here we
systematically modify the sequence of these proteins toward the homomeric human
α7 nAChR. These chimeric proteins exhibit a shift in affinities to reflect α7
binding characteristics yet maintain expression levels and stability conducive
for crystallization. We also present a pentameric humanoid nAChR extracellular
domain with the structural determination of the α7 nAChR glycosylation site.
