1992 Fiscal Year Final Research Report Summary
Calcium-dependent protein in photoreceptor light-adaptation
| Project/Area Number |
03670064
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Neurophysiology and muscle physiology
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| Research Institution | Keio University School of Medicine |
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Principal Investigator |
KAWAMURA Satoru Keio University School of Medicine, Department of Physiology, Associate Professor, 医学部, 助教授 (80138122)
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| Project Period (FY) |
1991 – 1992
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| Keywords | S-Modulin / Rhodopsin / Visinin / Photoreceptor / Adaptation / Calcium / Recoverin / Phosphorylation |
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| Research Abstract |
Our resent work showed that photoreceptor light-adaptation in vertebrates is regulated by a calcium-dependent regulatory protein, S-modulin (sensitivity-modulating protein). In the present project, I found the followings.
1. S-modulin is a calcium-binding protein. By binding of calcium, a hydro-phobic portion emerges so that S-modulin binds to disk membranes to exert its physiologial function.
2. According to the partial amino acid sequence obtained from proteolyzed fragments, the amino acid sequence of S-modulin is about 60 % identical to visinin and 80 % to recoverin. Each of these three proteins has three putative EF hand structures. However, these proteins form a new family that is distinct from calmodulin family.
3. The site of S-modulin action in the phototransduction cascade is rhodopsin phosphorylation. At high calcium condition which is typical under dark-adapted condition, S-modulin inhibits rhodopsin phosphorylation so that the life time of activated rhodopsin is prolonged. By doing so, S-modulin prolongs photoreceptor light response and increases light-sensitivity in the dark.
From these results, one could elucidate most of the characteristics of the adaptation phenomena in vertebrate photoreceptor adaptation.
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