Metabotropic glutamate receptor 1 (mGluR1) is a 130 kDa, 7-transmembrane glycoprotein that belongs to group I of the C-family of G-protein coupled receptors. On neurons, mGluR1 is postsynaptic, associates with Gq-like proteins, mobilizes intracellular Ca++, and influences ion channel activity. Mature mGluR1 is 1176 amino acids (aa) in length and contains a 574 aa N-terminal extracellular domain (ECD) (aa 19-592). The ECD binds glutamate and forms either a covalent homodimer or heterodimer with CaSR. There is one alternative splice form for human mGluR1 that shows a 20 aa substitution for the C-terminal 308 amino acids. Over aa 33-522, human mGluR1 shares more that 98% aa identity with mouse, rat and canine mGluR1.