Fig. 5.

Model of the M₁ mAChR based on the crystal structure of the β₂-adrenergic receptor. The view is from outside of the TM helix bundle. Color-coding indicates the effects of the mutations of the residues studied on the potency and maximum signaling response of 77-LH-28-1: gray, little or no effect; green, reduced potency; red, reduced maximum signal; blue, increased potency. a, starting conformation showing the Trp101 side-chain in a trans conformation (χ1 = 167.7°). b, 77-LH-28-1 (magenta) docked into a binding pocket created by the isomerization of the side chain of Trp101 to a gauche⁺ conformation (χ1 = -66°).