G protein-coupled receptors

G protein-coupled receptors (GPCRs), also known as seven-(pass)-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptor, and G protein-linked receptors (GPLR), constitute a large protein family of receptors that detect molecules outside the cell and activate internal signal transduction pathways and, ultimately, cellular responses.

Pronunciation

• G protein-coupled receptors: /ˈdʒiː ˈproʊtiːn ˈkʌpld rɪˈsɛptərz/

Etymology

The term "G protein-coupled receptors" is derived from their association with G proteins, which get their name from the fact that they bind to guanine nucleotides.

Structure

GPCRs are integral membrane proteins that possess seven transmembrane domains. The extracellular parts of the receptor can be glycosylated. These extracellular loops also contain two highly conserved cysteine residues that form disulfide bonds to stabilize the receptor structure.

Function

GPCRs are involved in a wide variety of physiological processes. Some examples of their physiological roles include:

• The visual sense: The opsins use a photoisomerization reaction to translate electromagnetic radiation into cellular signals. Rhodopsin, for example, uses the conversion of 11-cis-retinal to all-trans-retinal for this purpose.
• The gustatory sense (taste): GPCRs in taste cells mediate release of gustducin in response to bitter-, umami- and sweet-tasting substances.
• The sense of smell: Receptors of the olfactory epithelium bind odorants (olfactory receptors) and pheromones (vomeronasal receptors)

Related Terms

• G proteins
• Transmembrane domain
• Signal transduction
• Cellular responses
• Opsins
• Rhodopsin
• Gustatory sense
• Olfactory epithelium
• Vomeronasal receptors

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