The Amino Terminal Domain ATD

Fig. 2. Membrane architecture of glutamate receptors. Ionotropic receptors are integral membrane spanning ion channels formed by the assembly of four or five subunits. Metabotropic glutamate receptors are G-pro-tein coupled receptors characterized by an unusually extended amino terminal domain (ATD).

Fig. 3. Architecture of ionotropic glutamate receptors. A single subunit is formed by three transmembrane domains, a membrane-reentering loop and an extended amino terminal domain (ATD). The N-terminal portion of ATD is homologous to LIVBP. The C-terminal portion of ATD and the S2 segment of the extracellular loop are homologous to LAOBP and constimte the ligand-binding domain.

Fig. 5. Architecture of metabotropic glutamate receptors. The first 400 amino acids of the ATD are homologous to LIVBP and include the ligand binding domain. The C-terminal portion of the ATD contains a cysteine-rich region which is responsible for the homodimerization of the receptor.

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