non-visual parapinopsin, member of the class A family of seven-transmembrane G protein-coupled receptors
This group includes the non-visual pineal pigment, parapinopsin, which is a member of the class A of the seven transmembrane G protein-coupled receptors. Parapinopsin serves as a UV-sensitive pigment for the wavelength discrimination in the pineal-related organs of lower vertebrates such as reptiles, amphibians, and fish. Although parapinopsin is phylogenetically related to vertebrate visual pigments such as rhodopsin, which releases its retinal chromophore and bleaches, the parapinopsin photoproduct is stable and does not bleach. The vertebrate non-visual opsin family includes pinopsins, parapinopsin, VA (vertebrate ancient) opsins, and parietopsins. These non-visual opsins are expressed in various extra-retinal tissues and/or in non-rod, non-cone retinal cells.