Photoreceptor required for image-forming vision at low light intensity. Required for photoreceptor cell viability after birth (By similarity). May use a mixture of retinal and 3-dehydroretinal as visual pigment (PubMed:5315587). Light-induced isomerization of 11-cis to all-trans retinal triggers a conformational change that activates signaling via G-proteins. Subsequent receptor phosphorylation mediates displacement of the bound G-protein alpha subunit by arrestin and terminates signaling (By similarity). Synthesized in the inner segment (IS) of rod photoreceptor cells before vectorial transport to disk membranes in the rod outer segment (OS) photosensory cilia. Retina. Localized in the ventral part of the retina. Contains one covalently linked retinal chromophore. Upon light absorption, the covalently bound 11-cis-retinal is converted to all-trans-retinal. After hydrolysis of the Schiff base and release of the covalently bound all-trans-retinal, active rhodopsin is regenerated by binding of a fresh molecule of 11-cis-retinal. Belongs to the G-protein coupled receptor 1 family. Opsin subfamily.