2000 Fiscal Year Final Research Report Summary
The regulatory mechanism of phototransduction pathway in rhabdomeric photoreceptors.
| Project/Area Number |
10640672
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
動物生理・代謝
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| Research Institution | Hyogo College of Medicine |
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Principal Investigator |
SUZUKI Tatsuo Hyogo College of Medicine, Faculty of Medicine, Associate Professor, 医学部, 助教授 (90068544)
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| Project Period (FY) |
1998 – 2000
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| Keywords | Cell signaling / Photoreceptor / Phototransduction / Rhodopsin / GTP-binding protein / Phospholipase C / Proteinkinase C |
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| Research Abstract |
1. Reconstitution system of rhodopsin/G protein/phospholipase C was established, and activation of phospholipase C was observed in the presence of GTP and light. It was experimentally confirmed in vitro that the rhodopsin/G protein/phospholipase C system is able to work as the major reaction pathway of phototransduction.
2. Under the light conditions, translocation of G protein from membrane to cytosol was found in two species, Procambarus and Octopus. The cytosolic type was an inactive form of G protein and it did not couple with rhodopsin. It was suggested that a fatty acid is attached to the membrane-bound form and unattached to the cytosolic form.
3. The C-terminal peptide of phospholipase C was cleaved by a calcium-dependent protease, and the truncated phospholipase C was not activated by G protein. It was directoly proved in reconstitution system that the C-terminal peptide is the regulatory domain of the enzyme.
4. cDNA of phospholipase C was cloned in Watasenia, which encoded a protein of M.W.125,670 (1, 112 amino acids). The protease-cleavage site was determined by mass spectrometry and amino acid sequencing to be N-terminal side of G(860), A(861) and K(863).
5. Proteinkinase C, which is activated by diacylglycerol and calcium, was isolated from squid retina. It was found that phospholipase C was efficiently phosphorylated by the purified proteinkinase C.
6. The results of this study suggested that the translocation of G protein and the limited proteolysis of phospholipase C are candidates of regulatory mechanism of phototransduction in rabdomeric photoreceptors.
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