| Project/Area Number |
06558096
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| Research Category |
Grant-in-Aid for Developmental Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Functional biochemistry
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| Research Institution | Institute of Molecular and Cellular Biosciences, University of Tokyo |
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Principal Investigator |
TOKUDA Hajime University of Tokyo, Institute of Molecular and Cellular Biosciences, Professor, 分子細胞生物学研究所, 教授 (40125943)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUYAMA Shin-ichi University of Tokyo, Institute of Molecular and Cellular Biosciences, Associate, 分子細胞生物学研究所, 助教授 (50183108)
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| Project Period (FY) |
1994 – 1995
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| Project Status |
Completed (Fiscal Year 1995)
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| Budget Amount *help |
¥18,700,000 (Direct Cost: ¥18,700,000)
Fiscal Year 1995: ¥8,100,000 (Direct Cost: ¥8,100,000)
Fiscal Year 1994: ¥10,600,000 (Direct Cost: ¥10,600,000)
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| Keywords | Overproduction of Sec factors / Protein secretion / E.coli / Chaperone / Precursor protein / SecG / Everted membrane vesicles / 酸性リン脂質 / SecA / SecB / 分泌型蛋白質 / 蛋白質分泌装置 / Sec因子大量発現 |
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| Research Abstract |
Preprotein translocase of E.coli comprises a peripheral component, SecA,and integral membrane components, SecY,SecE and SecG.SecA is thought to deliver the preprotein to the putative protein-conducting channel formed by SecY and SecE by undergoing ATP-driven cycles of membrane insertion and deinsertion. SecG renders the translocase highly efficient by unknown mechanism. Preprotein translocation into everted membrane vesicles is inhibited by an externally added antibody raised against the C-terminal region of SecG.However, we found that this region is exposed to the inside (periplasmic side) of membrane vesicles in the absence of preprotein translocation, thereby being protected from external proteinase K.Surprisingly, when preprotein translocation was started with ATP hydrolysis, the C-terminal region was exposed to the outside (cytoplasmic side) of membrane vesicles and thus digested by proteinase K.Another region of SecG showed a change in membrane sidedness, from the cytoplasmic to the periplasmic side, upon preprotein translocation, indicating that SecG undergoes topology inversion. This topology inversion was tightly coupled to the SecG function, and linked with the insertion-deinsertion cycle of SecA.We propose here that the inversion cycle of the SecG topology facilitates the insertion-deinsertion cycle of SecA,thereby causing efficient preprotein translocation.
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