GPCR Classification Sample Clauses

GPCR Classification. Further classification of the GPCR superfamily based on sequence homology and phylogenetic analysis yields five main subfamilies, Glutamate, Rhodopsin, Adhesion, Frizzled/Taste2 and Secretin (Fredriksson et al. 2003). The Rhodopsin family, also commonly referred to as class A (Xxxxxxxxxx 1994), is named for the first 7TM receptor identified, rhodopsin, the visual receptor for light (Xxxxxxxx et al. 1983; Ovchinnikov Iu et al. 1983). Approximately 90% of all GPCRs are members of the Rhodopsin family, more than half of which are olfactory receptors (Munk et al. 2016). While receptors in the Rhodopsin family typically have a short NT, their 7TM configuration and ligand preference are quite heterogeneous (Xxxxxxxxxx and Schioth 2008). The Secretin family of GPCRs contains 15 members, all of which contain an extracellular hormone-binding domain and bind peptide hormones. Secretin family members share relatively high homology, and contain several conserved residues (Xxxxxxxxxx and Schioth 2008). Contrary to the Rhodopsin receptors, much of the variation within the Secretin family occurs in the NT domain. The Adhesion family is the second largest family of GPCRs in humans, containing roughly 4% of all GPCRs. Adhesion receptors contain a variety of functional domains and nearly all members have long and diverse N-termini (Bjarnadottir et al. 2004). The most characteristic feature of Adhesion GPCRs is the GPCR proteolytic site (GPS) domain which acts as an intracellular autocatalytic processing resulting in two non-covalently attached fragments of the receptor (Xxxxxxxxxxx et al. 1997). The Adhesion and Secretin families are often categorized together into class B type receptors (Xxxxxxxxxx 1994). In addition to eight metabotropic glutamate receptors, the Glutamate, or class C, family of GPCRs includes GABAB receptors, calcium-sensing receptors, taste receptors and seven orphan receptors (Bjarnadottir, Fredriksson, and Schioth 2005). Glutamate family members share two unique features, they possess an unusually large extracellular NT domain containing a Venus flytrap motif, and they form constitutive dimers (Rondard et al. 2011). The last family of receptors, the Frizzled/Taste2 receptors are also referred to as class F and T, respectively (Xxxxxxxxxx 1994). The Frizzled family consists of 10 Frizzled receptors and Smoothened, originally identified in drosophila (Xxxxxx and Xxxxx 1987; Xxxxx et al. 1994). Frizzled family members are atypical in that their canonical ...