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. Author manuscript; available in PMC: 2018 Feb 27.
Published in final edited form as: Annu Rev Pharmacol Toxicol. 2012 Sep 28;53:127–146. doi: 10.1146/annurev-pharmtox-010611-134548

Figure 2.

Figure 2

Figure 2

(a) The G protein–coupled receptors (GPCRs) classified according to the GRAFS system (named on the basis of its five main classes: Glutamate, Rhodopsin, Adhesion, Frizzled, and Secretin). The numbers indicate the approximate numbers of receptors in the different classes. The ligands of the Glutamate and Secretin receptors are also indicated. (b) Schematic representation of the phylogenetic relationships of the human Rhodopsin GPCRs. The phylogenetic relationships are based on those discussed in Reference 83. Orphan GPCRs are shown in red. Some GPCR subgroups, analyzed as separate groups in Reference 83, have been placed according to their phylogenetic positions as described in Reference 85. Encircled areas outline phylogenetic clusters. Receptors with ambiguous relationships to other members are indicated by a dotted line.