NMDAR1: Proteins and Enzymes

N-methyl-D-aspartate (NMDA) receptors are ligand-gated ion channels that have a high permeability to calcium found in the central nervous system. The receptor consists of a number of distinct ligand binding domains, and the presence of both glutamate and glycine are required for full activation of the channel. Within the channel there is also a binding site for magnesium, which, when occupied, propagates a voltage-dependent channel block. Other binding sites are also found in the receptor, including a zinc-binding site and an inter-channel site that binds specific channel blockers such as phencyclidine (PCP) and related compounds. The NMDA receptor has been demonstrated to play an essential role in long-term potentiation (LTP), a phenomenon that has been implicated to be the basis for learning and memory. The influx of calcium as a result of channel activation is thought to be responsible for neuronal plasticity and glutamate neurotoxicity. A number of different NMDA receptor subunits have been cloned that may possess different functional and localization properties. The NMDA-R1 subunit (NR1) is expressed throughout the brain, while the NMDA-R2 subunits (NR2A, NR2B, NR2C, and NR2D) have a more specific localization pattern. The NMDA receptor subunits differ also in glycine sensitivity, the relative strength of the magnesium channel block, and their respective agonist-dependent deactivation time.