| Project/Area Number |
11480188
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Biophysics
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| Research Institution | Tokyo University of Agriculture and Technology |
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Principal Investigator |
MITAKU Shigeki Faculty of Engineering, Professor, 工学部, 教授 (10107542)
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| Co-Investigator(Kenkyū-buntansha) |
SONOYAMA Masashi Tokyo University of Agriculture and Technology Faculty of Engineering, Assistant Professor, 工学部, 助手 (40242242)
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| Project Period (FY) |
1999 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥15,800,000 (Direct Cost: ¥15,800,000)
Fiscal Year 2001: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2000: ¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 1999: ¥11,500,000 (Direct Cost: ¥11,500,000)
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| Keywords | Membrane proteins / Molecular structure / Intermediate states / Long range interaction / Coarse graining / Protein denaturation / Structure prediction / Protein classification / 構造安定性 / 光誘起変性 / プローブヘリックス法 / 相互作用 / バクテリオロドプシン / 膜貫通ヘリックス / レチナール / 膜タンパク質構造予測 / 膜貫通ヘリックス配置 / 極性相互作用 / 物理化学的予測 / 格子モデル |
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| Research Abstract |
The function of a protein is expressed through the structural change or fluctuation. In this work, we studied experimentally and theoretically the mechanism of the structural change of membrane proteins, using bacteriorhodopsin as a model system of the membrane protein.
We measured the denaturation behaviors of bacteriorhodopsin, a typical intrinsic membrane protein, changing the temperature and the light illumination conditions. At room temperature, the structure of bacteriorhodopsin recovered from photointermediate states to the ground state, while the recovery from the excited states was incomplete at the temperature around 50 ℃. We could conclude from extensive photobleaching experiments at various temperatures that the structure of bacteriorhodopsin is partly stabilized by polar loop segments which particularly contribute to the recovering process of the photocycle. Further experiments of the photobleaching at high temperature for mutated and chemically modified bacteriorhodopsin w
… More
ill lead to the physical mechanism of the photocycle.
A novel method for theoretical structure prediction was developed on the basis of the preivious results of denaturation experiments. Supposing that seven transmembrane helices are continuum rods with the polarity distribution of their surfaces, we calculated the interaction energy of a seven-helix system. The positioning and orientation of seven helices could be predicted by minimizing the interaction energy. The most preferable configuration of helices was very similar to the actual structure of bacteriorhodopsin. In the framework of this method, the protonation and deprotonation of amino acid residues within the helical regions strongly affect the helix configuration. In fact, the calculation suggested that the positioning and the tilting of helices change during the photocycle in accordance with the structural analyzes of intermediate states of bacteriorhodopsin. The problem of the contribution of loop segments to the structural change should be solved for the understanding of the functioning mechanism. Less
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