Open AccessA Newly Discovered Visual Cycle Necessary for Vision during Continuous Illumination
Author(s) -
George Wolf
Publication year - 2002
Publication title -
nutrition reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.958
H-Index - 150
eISSN - 1753-4887
pISSN - 0029-6643
DOI - 10.1301/00296640260085976
Subject(s) - rhodopsin , retinal , visual phototransduction , retinol , retinaldehyde , retina , photoisomerization , biology , chemistry , biochemistry , neuroscience , vitamin , isomerization , catalysis
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.