Fig. 2.

Structural comparison of M₁ to M₅ mAChRs. (A) The overall view of the M₁ to M₅ mAChR structures aligned with the M₅ mAChR and shown as cartoons. M₁•tiotropium is colored peach (PDB ID code 5CXV), M₂•NMS in dark blue (PDB ID code 5ZKC), M₂•AF-DX384 in yellow (PDB ID 5ZKB), M₃•tiotropium in light blue (PDB ID 4U15), M₄•tiotropium in pink (PDB ID 5DSG) and M₅•tiotropium in green (PDB ID 6OL9). (B) Comparison of residues (stick representation) lining the orthosteric site with tiotropium from the M₅ mAChR displayed and (C) overlay of the orthosteric ligands. (D) View from the extracellular surface comparing differences in the ECL regions across the M₁ to M₅ mAChRs. Distances between the backbone of M₁ and M₅ mAChR residues in ECL2 and ECL3 are shown and indicated by arrows. (E) Electrostatic and surface potential of M₂ and M₅ mAChR (+5kT/e in blue and −5kT/e in red) mapped on the surface of the receptors calculated at pH 7.0. (F) Comparison of dissociation rate and (G) dissociation half-life of [³H]NMS by the addition of 10 µM atropine at the M₂ and M₅ mAChRs. Values are significantly different (P value < 0.0001, 2-way ANOVA). Detailed statistical analysis is shown in SI Appendix, Table S5.