The ligand-binding domain of the NR1 subunit of ionotropic NMDA (N-methyl-D-aspartate) glutamate receptors, a member of the type 2 periplasmic binding fold protein superfamily.
This group contains the ligand binding domain of the NR1, an essential channel-forming subunit of the NMDA receptor. The ionotropic N-methyl-d-asparate (NMDA) subtype of glutamate receptors serves critical functions in neuronal development, functioning, and degeneration in the mammalian central nervous system. The functional NMDA receptor is a heterotetramer ccomposed of two NR1 and two NR2 (A, B, C, and D) or of 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. When co-expressed with NR1, the NR3 subunits form receptors that are activated by glycine alone and therefore can be classified as excitatory glycine receptors. NR1/NR3 receptors are calcium-impermeable and unaffected by ligands acting at the NR2 glutamate-binding site.
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