Left, localization of site 5 at the interface between the two constitutive ABD dimers. Right top, crystal structures of the inhibited (PDB 5IOV; Zhu et al, 2016) and presumably active (5FXG; Tajima et al, 2016) states illustrating the differences in distances between GluN2B-L795 and GluN1-E698 or GluN1-R673 at interface 5. Those three residues are colored green, while GluN1 and GluN2B subunits are colored red and blue respectively. Right bottom, schematic representation of the GluN1-R673C/GluN2B-L795C disulfide cross-link capturing an inhibited state of the receptor, and of the GluN1-E698C/GluN2B-L795C disulfide cross-link trapping the rolling motion 