N-terminal leucine/isoleucine/valine-binding protein (LIVBP)-like domain of the non-NMDA (N-methyl-d-asparate) subtypes of ionotropic glutamate receptors
N-terminal leucine/isoleucine/valine-binding protein (LIVBP)-like domain of the non-NMDA (N-methyl-d-asparate) subtypes of ionotropic glutamate receptors. While this N-terminal domain belongs to the periplasmic-binding fold type I superfamily, the glutamate-binding domain of the iGluR is structurally homologous to the periplasmic-binding fold type II. The LIVBP-like domain of iGluRs is thought to play a role in the initial assembly of iGluR subunits, but it is not well understood how this domain is arranged and functions in intact iGluR. Glutamate mediates the majority of excitatory synaptic transmission in the central nervous system via two broad classes of ionotropic receptors, characterized by their response to glutamate agonists: N-methyl-d -aspartate (NMDA) and non-NMDA receptors. NMDA receptors have intrinsically slow kinetics, are highly permeable to Ca2+, and are blocked by extracellular Mg2+ in a voltage-dependent manner. Non-NMDA receptors have faster kinetics, are most often only weakly permeable to Ca2+, and are not blocked by extracellular Mg2+. While non-NMDA receptors typically mediate excitatory synaptic responses at resting membrane potentials, NMDA receptors contribute several forms of synaptic plasticity and are thought to play an important role in the development of synaptic pathways. Non-NMDA receptors include alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionate (AMPA) and kainate receptors.