Overall view of crystal structure of Ls-AChBP complexed with imidacloprid (IMI). The pentameric structure of Ls-AChBP is viewed from the top (a) corresponding to an extracellular surface of nAChRs and from the side (b). IMI molecules bound to Ls-AChBP are shown in space-filling model, whereas carbons, nitrogens and oxygens are colored green, blue and red, respectively. Two subunits, A and B chains, are colored by pink and blue, respectively. c The structure of A–B domain boundary of the Ls-AChBP complexed with IMI (red) is compared with that of the Ls-AChBP complexed with CTD (blue) and the apo form (light brown) complexed with 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) (PDB entry code: 1UX2) (Celie et al. 2004). Ligands are presented by stick models