Figure 3.

Aniracetam and CX614 bind in the dimer interface, in a crevice at the clamshell hinge. A, View down the twofold axis, showing the binding of aniracetam, in one of its two equivalent orientations. Protomer A is in green, protomer B is in blue, and aniracetam is drawn in Corey, Pauling, and Koltun (CPK) representation, as is the partial agonist fluorowillardiine. B, View of the Ani/FW complex perpendicular to the molecular twofold axis. Here, aniracetam is red and in CPK representation; the approximate positions of the “linker” that connects the ligand-binding cores to the transmembrane domains is shown. C, View of the CX614 complex, along the molecular twofold axis, with the protein subunits colored as in A and CX614 and quisqualate in CPK representation. D, Illustration of CX614 binding pocket using the same view as in C, with CX614 in red.