A newly discovered visual cycle necessary for vision during continuous illumination.
Rhodopsin, the light-sensitive visual pigment of the retina, is activated through photoisomerization of its prosthetic group, 11-cis-retinal, to all-trans-retinal. A protein found in the retinal pigment epithelium named retinal G protein- coupled receptor (RGR) reacts to light in an opposite but parallel way: its prosthetic group, all-trans-retinal, is photoisomerized to 11-cis-retinal. The latter is reduced to 11-cis-retinol by a cis-retinol dehydrogenase that co-purifies with the RGR. The resulting 11-cis-retinol feeds into the visual cycle to be oxidized to 11-cis-retinal, thus replenishing the 11-cis-retinal of the rhodopsin. During continuous intense illumination, RGR can supplement the 11-cis-retinal required to regenerate rhodopsin.
Wolf
George
G
Department of Nutritional Sciences and Toxicology, University of California, Berkeley 94720-3104, USA.
D000818:Animals; D002417:Cattle; D005136:Eye Proteins / Q000502:physiology*; D006801:Humans; D008029:Lighting; D051379:Mice; D011956:Receptors, Cell Surface / Q000502:physiology*; D043562:Receptors, G-Protein-Coupled; D012160:Retina / Q000502:physiology*; D012243:Rhodopsin / Q000502:physiology; D014785:Vision, Ocular / Q000502:physiology*
D005136:Eye Proteins; C089754:G protein-coupled receptor RGR; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D012243:Rhodopsin