The class C G-protein-coupled receptors (IPR000337) are a class of G-protein coupled receptors that include the metabotropic glutamate receptors (IPR000162) and several additional receptors. Family C GPCRs have a large extracellular N-terminus which binds the orthosteric (endogenous) ligand. The shape of this domain is often likened to a clam. Several allosteric ligands to these receptors have been identified and these bind within the seven transmembrane region. (hgnc.genefamily:275)