a, Cryo-EM density map of splayed GluD1 model is shown in a view parallel to the membrane. The four subunits A, B, C, D are colored in orange, green, yellow and cyan, respectively. The colored spheres represent the COM of ATD and LBD domains. b, Top view of ATD with segmented EM density map fitted with atomic models is shown. The distances between the COMs of ATDs are shown with dashed lines below the EM density map, depicting the arrangement of ATDs in the plane. c, Densities corresponding to LBDs fitted with atomic models is shown. d, The distances from COMs of ATD and LBD are shown. The LBD plane is depicted as a circular disk, and the ATD plane is shown as a dashed ellipse. e,f, Side and top views of angles subtended by COMs of ATD with the COM of the LBD layer. COM plane of the LBD layer is indicated by metallic disk.