title: Class C GPCR
text: # Class C GPCR
  
  The class C G-protein-coupled receptors (InterPro: IPR000337) are a class of G-protein coupled receptors that include the metabotropic glutamate receptors (InterPro: IPR000162) and several additional receptors.
  
  Structurally they are composed of four elements; an N-terminal signal sequence; a large hydrophilic extracellular agonist-binding region containing several conserved cysteine residues which could be involved in disulphide bonds; a shorter region containing seven transmembrane domains; and a C-terminal cytoplasmic domain of variable length. This protein family includes metabotropic glutamate receptors, the extracellular calcium-sensing receptors, the gamma-amino-butyric acid (GABA) type B receptors, and the vomeronasal type-2 receptors.
  
  ## Subfamilies
  
  ### Calcium-sensing receptor-related
  
  * extracellular calcium-sensing receptor-related InterPro: IPR000068
     * Calcium-sensing receptor (CASR)
     * GPRC6A (GPRC6A)
  
  ### $GABA_B$ receptors
  
  * $GABA_B$ receptor (gamma-aminobutyric acid) InterPro: IPR002455
     * $GABA_B$ receptor 1 (GABBR1)
     * $GABA_B$ receptor 2 (GABBR2)
  
  ### Metabotropic glutamate receptors
  
  * Metabotropic glutamate receptors (mGluR) InterPro: IPR000162
     * $mGluR_1$ (GRM1)
     * $mGluR_2$ (GRM2)
     * $mGluR_3$ (GRM3)
     * $mGluR_4$ (GRM4)
     * $mGluR_5$ (GRM5)
     * $mGluR_6$ (GRM6)
     * $mGluR_7$ (GRM7)
     * $mGluR_8$ (GRM8)
  
  ### RAIG
  
  * Retinoic acid-inducible orphan G protein-coupled receptors (RAIG)
     * $RAIG_1$ (GPRC5A)
     * $RAIG_2$ (GPRC5B)
     * $RAIG_3$ (GPRC5C)
     * $RAIG_4$ (GPRC5D)
  
  ### Taste receptors
  
  * Taste receptor
     * Taste receptor, type 1, member 1 (TAS1R1)
     * Taste receptor, type 1, member 2 (TAS1R2)
     * Taste receptor, type 1, member 3 (TAS1R3)
  
  ### Orphan
  
  * Class C Orphan receptors
     * GPR158 (GPR158)
     * GPR179 (GPR179)
     * GPR156 (GPR156)
  
  ### Other
  
  * Bride of sevenless protein InterPro: IPR002956
  * Vomeronasal receptor, type 2 InterPro: IPR004073
  