Cryo-EM density maps of GluN1-N2B di-eNMDAR. GluN1, GluN2A, and GluN2B subunits are colored in gray, orange, and lavender, respectively. GluN1-Fab4F11, GluN2A-Fab28C, GluN2B-Fab2, N-linked glycans, and the antagonist (R)-CPP are colored in blue, mint, pink, purple, and gold, respectively. The overall architecture of eNMDAR is shown, with the three layers comprising the N-terminal domain (NTD), ligand-binding domain (LBD), and transmembrane domain (TMD), and displayed in side views (upper) and top-down views (bottom). In the upper panel of (C), the bilobed clamshells of the NTD and LBD are marked with R1/R2 and D1/D2 lobes, respectively. The 2D class averages in (A) and (B) show the representative top-down views, with colored arrowheads highlighting the Fab density (scale bar, 50 A).
