The ligand-binding domain of the NMDA (N-methyl-D-aspartate) subtype of ionotropic glutamate receptors, a member of the type 2 periplasmic binding fold protein superfamily.
The ligand-binding domain of the ionotropic NMDA subtype is structurally homologous to the periplasmic-binding fold type II superfamily, while the N-terminal domain belongs to the periplasmic-binding fold type I. The function of the NMDA subtype receptor serves critical functions in neuronal development, functioning, and degeneration in the mammalian central nervous system. The functional NMDA receptor is a heterotetramer comprising two NR1 and two NR2 (A, B, C, and D) or NR3 (A and B) subunits. The receptor controls a cation channel that is highly permeable to monovalent ions and calcium and exhibits voltage-dependent inhibition by magnesium. Dual agonists, glutamate and glycine, are required for efficient activation of the NMDA receptor. Among NMDA receptor subtypes, the NR2B subunit containing receptors appear particularly important for pain perception; thus NR2B-selective antagonists may be useful in the treatment of chronic pain.
Jiyao W et al.(2023). "The conserved domain database in 2023.",