Rhodopsin-like receptors

G Protein-Coupled Receptors (GPCRs), also called 7TM receptors, are the largest and most important integral membrane protein families, which mediate cellular responses to most hormones, metabolites, cytokines, and neurotransmitters, and therefore serve as “fruitful targets” for drug discovery. G Protein Coupled Receptors (GPCRs) perceive many extracellular signals and transduce them to heterotrimeric G proteins, which further transduce these signals intracellular to appropriate downstream effectors and thereby play an important role in various signaling pathways. GPCRs are categorized into six classes based on sequence and function: rhodopsin-like receptors (family A), secretin-like (family B), glutamate (family C), fungal mating pheromone receptors (Class D), cAMP receptors (Class E) and frizzled/smoothened (Class F). Class A GPCRs, rhodopsin-like receptors, is the largest group of GPCRs for a large variety of stimuli, which includes biogenic amine neurotransmitters, neuropeptides, peptide hormones, light, nucleotides, prostaglandins, leukotrienes, chemotactic peptides, and chemokines receptors. This family consists of 719 members and accounts for around 80% of GPCRs. The rhodopsin-like GPCRs show a conventional transmembrane domain (TMD) that forms ligand-binding pocket and additional eight helices with a palmitoylated cysteine at the C terminal.