Opsin protein

Opsin proteins are a diverse group of G protein-coupled receptors (GPCRs) that serve as light-sensitive receptors in animal tissues, most prominently in the photoreceptor cells of the retina[1][5][8]. Each opsin consists of seven transmembrane helices and binds a chromophore (typically 11-cis-retinal), which, upon photon absorption, isomerizes and triggers a conformational change, activating the G protein-mediated signal transduction pathway fundamental to vision and other light-responsive biological processes[1][8][5]. In vertebrates, they enable sight, while non-visual opsins (such as melanopsin) are crucial for circadian rhythm regulation and other non-image-forming photoreceptive functions[1][3]. Opsins are organized into multiple subfamilies according to sequence, G-protein-coupling specificity, and biological role; their functional diversity covers vision, circadian entrainment, pigmentation, taste, thermosensation, and more[3][7]. Opsin mutations are implicated in retinal dystrophies, color vision deficiencies, and may affect circadian behaviors; while no direct drugs target opsins clinically, they are central to optogenetic research where engineered opsins allow light-based modulation of cellular signaling[2][3][8].

Other names

Visual pigment proteinRetinylidene proteinPhotopigmentGPCR rhodopsin family protein

Light activation causing isomerization of chromophore, initiating G protein signaling cascades - In optogenetics, activation by light enables remote control of cell signaling