| Project/Area Number |
10680642
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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 |
Biophysics
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| Research Institution | Science University of Tokyo |
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Principal Investigator |
KOZONO Haruo Sci.Univ.Tokyo, Res.Inst.Biol.Sci, Associate Professor, 生命科学研究所, 助教授 (80287482)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAMURA Haruki Osaka Univ., Inst.Protein Res., Professor, 蛋白質研究所, 教授 (80134485)
FURUKAWA Koji Sci.Univ.Tokyo, Res.Inst.Biol.Sci, Res.Associate, 生命科学研究所, 助手 (00297631)
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| Project Period (FY) |
1998 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 1999: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1998: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Keywords | TCR / MHC / DSC / CD / peptide exchange / enthalpy / entropy / folding / ペプチド交換 / 熱安定性 / 酸性小胞 / 熱測定 / アゴニスト / アンタゴニスト |
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| Research Abstract |
Professional antigen presenting cell present peptide antigens in the context of major histocompatibility complex class II proteins (MHC II). The peptides are the end products of the proteins that came from extracellular fluid, which subsequently degraded in acidic vesicles. MHC II are synthesized in ER in which it binds invariant chain (Ii). A part of Ii named CLIP bind to the peptide-binding groove of MHC II. It is believed that low pH of acidic vesicle have important roll in peptides exchange reaction.
Here, we studied pH dependent stability of MHC II-peptide by thermodynamic way in order to uncover energetic as well as structural factors involved in the peptides exchange reaction. Peptides modified in one amino acid as well as whole sequence level are also studied. MHC II I-EィイD1kィエD1, MHC II I-AィイD1bィエD1, and as a control IgM are subjected to differential scanning calorimeter (DSC) and circular dichroism (CD) measurement. In both DSC and CD measurements, MHC II are more stable in acidic circumstance (pH5) than neutral one (pH7). In contrast, IgM is more stable in neutral pH. This observation was astonishing, since we expected that MHC II is unstable in pH5. Rationally, to exchange peptides MHC II must open some part of molecule so that stability should become lower. In addition, the stability gain in low pH is driven by enthalpy. The one amino acid change entropically affected to the stability.
We concluded as below. 1)The stability gain in low pH is a specific feature of MHC II ; the main function of MHC II is presentation of peptide at the cell surface, thus degradation in acidic vesicle should be prevented. 2)The fact that enthalpic stability gain in low pH suggests that some part, besides the peptide binding groove, increase interactions between domains. 3)Since peptides sequence modification affected to the stability of the MHC II, it is suggested that peptide became a part of protein.
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