OPN3 (Opsin 3) is a Protein Coding gene. Among its related pathways are Peptide ligand-binding receptors and Circadian rythm related genes. GO annotations related to this gene include G-protein coupled receptor activity and G-protein coupled photoreceptor activity. An important paralog of this gene is RHO.Opsins are members of the guanine nucleotide-binding protein (G protein)-coupled receptor superfamily. In addition to the visual opsins, mammals possess several photoreceptive non-visual opsins that are expressed in extraocular tissues. This gene, opsin 3, is strongly expressed in brain and testis and weakly expressed in liver, placenta, heart, lung, skeletal muscle, kidney, and pancreas. The gene may also be expressed in the retina. The protein has the canonical features of a photoreceptive opsin protein.