Related Experiment Videos
Molecular mechanisms in visual pigment regeneration
1Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115.
Photochemistry and Photobiology
|December 1, 1992
Summary
Vision requires retinoid isomerization. This study reveals membrane phospholipids power the enzymatic conversion of all-trans-retinyl esters to 11-cis-retinol, enabling vision restoration.
Area of Science:
- Biochemistry
- Molecular Biology
- Vision Science
Background:
- Photochemical bleaching of rhodopsin involves 11-cis-retinal isomerization.
- Vision requires enzymatic trans to cis retinoid isomerization.
- Multiple retinoid forms and energy requirements complicate this process.
Purpose of the Study:
- To identify the energy source and mechanism for retinoid isomerization in vision.
- To elucidate the enzymatic pathway for regenerating the visual chromophore.
Main Methods:
- Investigated enzymatic esterification of all-trans-retinol by lecithin retinol acyl transferase.
- Characterized the isomerohydrolase enzyme responsible for transforming all-trans-retinyl esters to 11-cis-retinol.
Main Results:
- Identified a two-step process utilizing membrane phospholipids for energy.
- Demonstrated esterification of all-trans-retinol to all-trans-retinyl ester.
- Showed direct conversion of the ester to 11-cis-retinol by an isomerohydrolase, coupling hydrolysis energy.
Conclusions:
- Membrane phospholipids provide the energy for retinoid isomerization.
- A specific enzymatic pathway involving ester intermediates regenerates the visual chromophore.
- This mechanism efficiently drives the formation of the high-energy 11-cis-retinoid isomer.