| Project/Area Number |
03454020
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
動物発生・生理学
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| Research Institution | The University of Tokyo |
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Principal Investigator |
ISHIKAWA Hajime The University of Tokyo, Graduate School of Science, Professor, 大学院・理学系研究科, 教授 (70012482)
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| Co-Investigator(Kenkyū-buntansha) |
SASAKI Tetsuhiko The University of Tokyo, Graduate School of Science, Instructor, 大学院・理学系研究科, 助手 (60235257)
YAMASHITA Tetsuro The University of Tokyo, Graduate School of Science, Instructor, 大学院・理学系研究科, 助手 (20202377)
藤原 晴彦 東京大学, 理学部, 講師 (40183933)
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| Project Period (FY) |
1991 – 1993
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| Project Status |
Completed (Fiscal Year 1993)
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| Budget Amount *help |
¥6,300,000 (Direct Cost: ¥6,300,000)
Fiscal Year 1993: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1992: ¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1991: ¥3,000,000 (Direct Cost: ¥3,000,000)
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| Keywords | Intracellular Symbiosis / Chaperonin / Energy-Coupling / Histidine Protein Kinase / Glutamine / Adaptive Molecular Evolution / Gut Microbes / 分子進化 / ツノアブラ族 / 共生体置換 / ヒスチジン・タンパク質キナーゼ / リン酸化 / 窒素再循環系 / 消化共生 / アブラムシ / 細胞内共生体 / シンビオニン / symオペロン / 自己触媒活性 / 分子シャペロン / 有機窒素再循環 |
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| Research Abstract |
1. Symbionin, an aphid endosymbiont-specific protein, is an energy-coupling protein which undergoes autophosphorylation in the presence of high-energy phosphate compounds and transfers its phosphate group to other acceptor compounds. While this property of symbionin is reminiscent of that of histidine protein kinases in the tow-component system that transduces environmental signals in E.coli, no considerable homology between the two proteins is apparent.
2. It has been suggested that symbionin is phophorylated at His-133, where GroEL has Ala instead of His. Since between the two proteins the overall amino acid sequence is highly conserved, it is all the more conspicuous that symbionin has created His at this position as the result of three consecutive base substitutions of a codon for Ala in GroEL.It is possible that symbionin has acquired a new function through positive selection in favor of His at this position, suggesting that adaptive evolution is in action even at molecular level.
3. While in the groE operon the expression of GroES and GroEL are comparable with each other, in the aphid endosymbiont the expression of GroES homolog is disproportionately less than that of symbionin.
4. In the synthesis of essential amino acids by the endosymbiont using glutamine, glutamine is first converted into glutamate and ammonia in the bacteriocyte and then absorbed by the symbiont.
5. One of gut microbes of aphid resembles E.coli, but prefers lower temperatures than does the latter. Comparison of structure of several genes suggested that the gut microbe is phylogenetically closer to the endosymbiont than is E.coli.
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