neuropsin (Opsin-5), member of the class A family of seven-transmembrane G protein-coupled receptors
Neuropsin, also known as Opsin-5, is a photoreceptor protein expressed in the retina, brain, testes, and spinal cord. Neuropsin belongs to the type 2 opsin family of the class A G-protein coupled receptors. Mammalian neuropsin activates Gi protein-mediated photo-transduction pathway in a UV-dependent manner, whereas, in non-mammalian vertebrates, neuropsin is involved in regulating the photoperiodic control of seasonal reproduction in birds such as quail. As with other opsins, it may also act as a retinal photoisomerase.