The goal of the proposed research is to elucidate the molecular mechanism of visual excitation in vertebrate retinal rods. Phototransduction is now known to involve a light-activated enzyme cascade that leads to a rapid reduction of cytosolic cycli GMP and the closure of Na+ channels at the plasma membranes. Central to this process is the activation of three proteins: transducin, cyclic GMP phosphodiesterase, and a postulated cyclic GMP-sensitive channel. The goal of this study is to gain and understanding of the molecular basis of photoexcitation through detailed strucutral and functional analyses of these retinal proteins. We propose to carry out the following studies: (1) Specific monoclonal antibody probes directed against transducin and phosphodiesterase will be used to investigate the structure-function relationships of these proteins, to localize their distributions in photoreceptors, and to study the cause of retinal degenerations. (2) Site-directed chemical probes and anti-synthetic peptdie antibodies will be developed to identify and study the active sites of transducin, and to characterize other cellular GPT-binding homologs. (3) The interaction of the lambda inhibitor and cyclic GMP with phosphodiesterase will be invesigated. The primary structure of the phosphodiesterase subunits will be elucidated by recombinant DNA techniques. (4) Finally, an attempt will be made to isolate and identify the cyclic GMP-sensitive channel. By advancing our knowledge in these four specific areas, our research is expected to contribute to the overall goal of achieving a better understanding of how the interactions of these proteins give rise to activation and termination of the photoresponse in visual cells.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY005895-10
Application #
2159638
Study Section
Visual Sciences A Study Section (VISA)
Project Start
1984-12-01
Project End
1996-11-30
Budget Start
1993-12-01
Budget End
1994-11-30
Support Year
10
Fiscal Year
1994
Total Cost
Indirect Cost
Name
University of California Los Angeles
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
119132785
City
Los Angeles
State
CA
Country
United States
Zip Code
90095
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Lee, R H; Lieberman, B S; Yamane, H K et al. (1992) A third form of the G protein beta subunit. 1. Immunochemical identification and localization to cone photoreceptors. J Biol Chem 267:24776-81
Fung, B K; Lieberman, B S; Lee, R H (1992) A third form of the G protein beta subunit. 2. Purification and biochemical properties. J Biol Chem 267:24782-8
Anant, J S; Ong, O C; Xie, H Y et al. (1992) In vivo differential prenylation of retinal cyclic GMP phosphodiesterase catalytic subunits. J Biol Chem 267:687-90
Yamane, H K; Farnsworth, C C; Xie, H Y et al. (1991) Membrane-binding domain of the small G protein G25K contains an S-(all-trans-geranylgeranyl)cysteine methyl ester at its carboxyl terminus. Proc Natl Acad Sci U S A 88:286-90
Fung, B K; Young, J H; Yamane, H K et al. (1990) Subunit stoichiometry of retinal rod cGMP phosphodiesterase. Biochemistry 29:2657-64
Fung, B K; Yamane, H K; Ota, I M et al. (1990) The gamma subunit of brain G-proteins is methyl esterified at a C-terminal cysteine. FEBS Lett 260:313-7
Yamane, H K; Farnsworth, C C; Xie, H Y et al. (1990) Brain G protein gamma subunits contain an all-trans-geranylgeranylcysteine methyl ester at their carboxyl termini. Proc Natl Acad Sci U S A 87:5868-72
Ong, O C; Ota, I M; Clarke, S et al. (1989) The membrane binding domain of rod cGMP phosphodiesterase is posttranslationally modified by methyl esterification at a C-terminal cysteine. Proc Natl Acad Sci U S A 86:9238-42
Griswold-Prenner, I; Tuteja, N; Farber, D B et al. (1989) G protein-effector coupling: interactions of recombinant inhibitory gamma subunit with transducin and phosphodiesterase. Biochemistry 28:6145-50

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