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.