GPCR families

The GPCRs have been divided into at least six families of GPCRs showing little to no sequence similarity:

Class A Rhodopsin like: Amine, Peptide, Hormone protein, (Rhod)opsin, Olfactory, Prostanoid, Nucleotide-like, Cannabinoid, Platelet activating factor, Gonadotropin-releasing hormone, Thyrotropin-releasing hormone & Secretagogue, Melatonin, Viral, Lysosphingolipid & LPA (EDG), Leukotriene B4 receptor, Class A Orphan/other.

Class B Secretin like: Calcitonin, Corticotropin releasing factor, Gastric inhibitory peptide, Glucagon, Growth hormone-releasing hormone, Parathyroid hormone, PACAP, Secretin, Vasoactive intestinal polypeptide, Diuretic hormone, EMR1, Latrophilin, Brain-specific angiogenesis inhibitor (BAI), Methuselah-like proteins (MTH), Cadherin EGF LAG (CELSR).

Class C Metabotropic glutamate / pheromone: Metabotropic glutamate, Calcium-sensing like, Putative pheromone receptors, GABA-B, Orphan GPCR5, Orphan GPCR6, Bride of sevenless proteins (BOSS), Taste receptors (T1R).

Class D Fungal pheromone: Fungal pheromone A-Factor like (STE2,STE3), Fungal pheromone B like (BAR,BBR,RCB,PRA), Fungal pheromone M- and P-Factor, Fungal pheromone other.

Class E cAMP receptors (Dictyostelium):

Frizzled/Smoothened family: frizzled, Smoothened,

Putative families: Ocular albinism proteins, Insect odorant receptors, Plant Mlo receptors, Nematode chemoreceptors, Vomeronasal receptors (V1R & V3R), Taste receptors T2R.

Orphans: Putative / unclassified GPCRs.

Non-GPCR families: Class Z Bacteriorhodopsins