GPCR classes

Class A · Rhodopsin

The largest class by far — aminergic, peptide, lipid, nucleotide and chemokine receptors, plus the opsins. Most approved GPCR drugs act here.

Class B1 · Secretin

Secretin-family receptors for large peptide hormones such as GLP-1, glucagon, and PTH. Major metabolic and endocrine targets.

Class B2 · Adhesion

Adhesion GPCRs with large extracellular domains and self-cleaving GAIN domains. Roles in development and immunity; largely under-explored.

Class C · Glutamate

Dimeric receptors with large Venus-flytrap ligand domains — metabotropic glutamate, GABA-B, calcium-sensing, and taste-1 receptors.

Class F · Frizzled

Frizzled and Smoothened receptors transducing Wnt and Hedgehog signalling. Central to development and oncology.

Class T2 · Taste 2

Bitter taste receptors, expressed in the tongue and, surprisingly, throughout the body.

Class O1 · Odorant (class I)

Human class I odorant receptors (the OR51/52/56 families) — the ancestral “fish-like” clade humans share with aquatic vertebrates. A small group, but all human genes.

Class O2 · Odorant (class II)

Human class II (“tetrapod”) odorant receptors — the single largest gene family in the human genome.

Class Other · Other