non-visual VA (vertebrate ancient) opsins, member of the class A family of seven-transmembrane G protein-coupled receptors
The vertebrate ancient (VA) opsin photopigments were originally identified in salmon and they appear to have diverged early in the evolution of vertebrate opsins. VA opsins are localized in the inner retina and the brain in teleosts. The vertebrate non-visual opsin family includes pinopsins, parapinopsin, VA (vertebrate ancient) opsins, and parietopsins. These non-visual opsins are expressed in various extraretinal tissues and/or in non-rod, non-cone retinal cells. They are thought to be involved in light-dependent physiological functions such as photo-entrainment of circadian rhythm, photoperiodicity, and body color change. The VA opsins belong the class A of the G protein-coupled receptors and possess seven-transmembrane (TM) alpha-helices interconnected by three extracellular and three intracellular loops.
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