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A newly discovered visual cycle necessary for vision during continuous illumination.
1Department of Nutritional Sciences and Toxicology, University of California, Berkeley 94720-3104, USA.
Nutrition Reviews
|February 21, 2002
Summary
Retinal G protein-coupled receptor (RGR) uses light to convert all-trans-retinal to 11-cis-retinal, supporting rhodopsin regeneration in the visual cycle.
Area of Science:
- Biochemistry
- Molecular Biology
- Vision Science
Background:
- Rhodopsin activation involves 11-cis-retinal photoisomerization.
- The visual cycle regenerates rhodopsin's chromophore.
Purpose of the Study:
- To elucidate the role of retinal G protein-coupled receptor (RGR) in retinal pigment epithelium.
- To understand RGR's light-dependent prosthetic group isomerization and its contribution to rhodopsin regeneration.
Main Methods:
- Investigated the photoisomerization of RGR's prosthetic group.
- Analyzed the enzymatic reduction of all-trans-retinal to 11-cis-retinol by co-purifying cis-retinol dehydrogenase.
- Traced the metabolic fate of 11-cis-retinol within the visual cycle.
Main Results:
- RGR photoisomerizes all-trans-retinal to 11-cis-retinal, mirroring rhodopsin's reaction.
- A co-purifying cis-retinol dehydrogenase reduces 11-cis-retinal to 11-cis-retinol.
- This 11-cis-retinol is utilized in the visual cycle to replenish rhodopsin's 11-cis-retinal.
Conclusions:
- RGR plays a crucial role in processing retinaldehyde isomers.
- RGR-mediated regeneration of 11-cis-retinal supplements rhodopsin replenishment, especially under intense light conditions.