We aim to understand the molecular basis for light activation, recovery and adaptation of visual receptors. Our approach is to determine the intermolecular coupling magnitudes, stoichiometries, speeds and mechanism that permit automatic amplification, shutoff and sensitivity reduction after pulses of activating illumination of rod outer segment (ROS) membrane preparations of several kinds: whole isolated ROS after in vivo activation, broken open after isolation, and reconstituted from purified protein constituents. We use absorption and fluorescence spectroscopy, pH recording of nucleotide hydrolysis, fast membrane-aqueous phase separation, radiolabelled tracer nucleotides, nucleotide HPLC analysis, kinetic and thermodynamic computerized analytic modeling to specify the roles of rhodopsin bleaching, G-proteins, cGMP phosphodiesterase, arrestin, rhodopsin kinase and nucleotide and phosphoryl transfer enzymes in this process. Knowledge of these details is essential to the diagnosis of molecular defects of diseased receptor function and will accelerate progress in understanding design and defects of all hormone- neurotransmitter receptor - G-protein internal messenger coupling processes of both brain and somatic tissue.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY000012-29
Application #
3255054
Study Section
Visual Sciences A Study Section (VISA)
Project Start
1979-12-01
Project End
1994-11-30
Budget Start
1991-12-01
Budget End
1992-11-30
Support Year
29
Fiscal Year
1992
Total Cost
Indirect Cost
Name
University of Pennsylvania
Department
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104