Molecular determinants of agonist discrimination by NMDA receptor subunits: analysis of the glutamate binding site on the NR2B subunit

Neuron. 1997 Mar;18(3):493-503. doi: 10.1016/s0896-6273(00)81249-0.


NMDA receptors require both L-glutamate and the coagonist glycine for efficient channel activation. The glycine binding site of these heteromeric receptor proteins is formed by regions of the NMDAR1 (NR1) subunit that display sequence similarity to bacterial amino acid binding proteins. Here, we demonstrate that the glutamate binding site is located on the homologous regions of the NR2B subunit. Mutation of residues within the N-terminal domain and the loop region between membrane segments M3 and M4 significantly reduced the efficacy of glutamate, but not glycine, in channel gating. Some of the mutations also decreased inhibition by the glutamate antagonists, D-AP5 and R-CPP. Homology-based molecular modeling of the glutamate and glycine binding domains indicates that the NR2 and NR1 subunits use similar residues to ligate the agonists' alpha-aminocarboxylic acid groups, whereas differences in side chain interactions and size of aromatic residues determine ligand selectivity.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 2-Amino-5-phosphonovalerate / pharmacology
  • Amino Acid Sequence
  • Binding Sites
  • Excitatory Amino Acid Agonists / pharmacology*
  • Glutamic Acid / metabolism*
  • Glutamic Acid / pharmacology
  • Glycine / pharmacology
  • Ion Channel Gating / drug effects*
  • Models, Molecular
  • Molecular Sequence Data
  • Piperazines / pharmacology
  • Receptors, N-Methyl-D-Aspartate / agonists*
  • Receptors, N-Methyl-D-Aspartate / chemistry
  • Receptors, N-Methyl-D-Aspartate / metabolism
  • Sequence Alignment
  • Sequence Homology, Amino Acid


  • Excitatory Amino Acid Agonists
  • Piperazines
  • Receptors, N-Methyl-D-Aspartate
  • Glutamic Acid
  • 2-Amino-5-phosphonovalerate
  • 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid
  • Glycine