11-cisRetinal is a chromophore that binds to opsin in the mammalian visual system as an inverse agonist forming the inactive conformation of rhodopsin. When 11-cisretinal absorbs a photon of light, it isomerizes to form all-trans retinal beginning the phototransduction cycle, which is the basis for mammalian vision. A G121L mutation in opsin allows 11-cisretinal to bind as a partial agonist and activate rhodopsin in the absence of light. In a moth model of carotenoid deficiency-induced low visual sensitivity, 11-cisretinal application to compound eyes restored visual sensitivity almost completely.
11-cisRetinol is an isomer of vitamin A . It is formed from vitamin A,viaatrans-retinyl ester intermediate, by the enzyme RPE65 in the retinal pigment epithelium and then converted to 11-cisretinal as part of the visual cycle.1,211-cisRetinol is an agonist of salamander and human red rod opsins expressed in COS cells and an inverse agonist of salamander red cone opsin, as well as human red and green cone opsins expressed in COS cells.3It promotes pigment formation in cone, but not rod, photoreceptors. 1.Rando, R.R.The biochemistry of the visual cycleChem. Rev.101(7)1881-1896(2001) 2.Guignard, T.J.P., Jin, M., Pequignot, M.O., et al.FATP1 inhibits 11-cis retinol formation via interaction with the visual cycle retinoid isomerase RPE65 and lecithin: Retinol acyltransferaseJ. Biol. Chem.285(24)18759-18768(2010) 3.Ala-Laurila, P., Cornwall, M.C., Crouch, R.K., et al.The action of 11-cis-retinol on cone opsins and intact cone photoreceptorsJ. Biol. Chem.284(24)16492-16500(2009)