Purity > 90% as determined by SDS-PAGE. MW: 20.2kDa. Partial: 1-36aa. N-terminal 6xHis-SUMO-tagged. Homo sapiens (Human). Photoreceptor required for image-forming vision at low light intensity. Required for photoreceptor cell viability after birth. Light-induced isomerization of 11-cis to all-trans retinal triggers a conformational change leading to G-protein activation and release of all-trans retinal.