The regulation of the fluxes and metabolism of vitamin A in the retina and retinal pigment epithelium is not yet well understood and is the subject of this grant request. Central to this problem are quantitative studies on certain enzymes and binding proteins which process vitamin A in the eye and which could be points of regulation. In this grant request we propose to study by chemical and biochemical means retinal ester esterase, synthetase, rhodopsin and certain of the retinol(al) binding proteins. The two enzymes will be purified to homogeniety and their mechanisms of action determined. In order to study these mechanisms a new quantitative assay system for these enzymes will be developed involving the transfer of the retinoids from small unilamellar vesicles (SUV's) to the protein. This assay will allow for the precise calculation of retinoid concentrations as well as providing a known and stable environment for them which allows for a meaningful calculation of thermodynamic and kinetic constants. This assay system should be generally useful for binding studies involving hydrophobic ligands. Having a quantitative assay for the enzymes in hand, we will determine whether they are regulated by light in the albino rat and frog. Highly specific, irreversible, mechanism-based inhibitors will be synthesized for these enzymes and they will be tested in vivo to determine their physiological roles. The same assay system mentioned above will be used to quantitatively measure the binding of the retinol(al)s to ascertain the retinol binding proteins and determine whether the activity of these proteins is regulated by light. Specific irreversible inactivators of these proteins will also be prepared and studied in vivo. Finally, new specific mechanism-based inactivators for opsin have been prepared. These will be primarily used to study how rhodopsins activity is regulated by light. Quantitative studies on the visible absorption spectra of these inhibitor(s) - opsin complexes will also be of interest in determining the mechanism(s) by which opsin perturbs the absorption spectra of bound chromophores.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY003624-05
Application #
3258020
Study Section
Visual Sciences A Study Section (VISA)
Project Start
1980-12-01
Project End
1986-11-30
Budget Start
1984-12-01
Budget End
1985-11-30
Support Year
5
Fiscal Year
1985
Total Cost
Indirect Cost
Name
Harvard University
Department
Type
Schools of Medicine
DUNS #
082359691
City
Boston
State
MA
Country
United States
Zip Code
Mondal, M S; Ruiz, A; Hu, J et al. (2001) Two histidine residues are essential for catalysis by lecithin retinol acyl transferase. FEBS Lett 489:14-8
Mondal, M S; Ruiz, A; Bok, D et al. (2000) Lecithin retinol acyltransferase contains cysteine residues essential for catalysis. Biochemistry 39:5215-20
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Perez-Sala, D; Gilbert, B A; Rando, R R et al. (1998) Analogs of farnesylcysteine induce apoptosis in HL-60 cells. FEBS Lett 426:319-24
Cho, J; Hamasaki, K; Rando, R R (1998) The binding site of a specific aminoglycoside binding RNA molecule. Biochemistry 37:4985-92
Hamasaki, K; Rando, R R (1998) A high-throughput fluorescence screen to monitor the specific binding of antagonists to RNA targets. Anal Biochem 261:183-90
Wang, Y; Hamasaki, K; Rando, R R (1997) Specificity of aminoglycoside binding to RNA constructs derived from the 16S rRNA decoding region and the HIV-RRE activator region. Biochemistry 36:768-79
Hamasaki, K; Rando, R R (1997) Specific binding of aminoglycosides to a human rRNA construct based on a DNA polymorphism which causes aminoglycoside-induced deafness. Biochemistry 36:12323-8

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