Opsin

Opsins are a large family of evolutionarily conserved G protein-coupled receptors, each composed of seven transmembrane helices and characterized by the ability to bind a light-sensitive chromophore (usually 11-cis-retinal). They are responsible for the initial steps of phototransduction—the conversion of light into chemical signals—in the visual systems of animals, but also serve roles in non-visual physiological processes such as circadian rhythms and tissue photoresponse. Each opsin interacts with a cognate G protein when activated by light, initiating downstream signaling cascades. The opsin family is diverse, encompassing several gene families (e.g., rhodopsin, cone opsins, melanopsin) and spanning a wide range of tissues and functions. While foundational to vision and light-dependent biology, the general term “opsin receptor” is not typically used for any single protein and instead describes a large, heterogeneous family.

Other names

visual pigmentlight-sensitive GPCRrhodopsin-like receptorrhodopsincone opsinmelanopsin

Ligand (retinal) binding and photoisomerization leading to G protein activation and initiation of intracellular signaling cascades