1993 Fiscal Year Final Research Report Summary
PHYSIOLOGICAL ROLES OF TWO GLUCOSE UPTAKE PATHWAYS DURING GROWTH PHASEIN ESCHERICHIA COLI
| Project/Area Number |
04808030
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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 |
代謝生物化学
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| Research Institution | YAMAGUCHI UNIVERSITY |
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Principal Investigator |
YAMADA Mamoru YAMAGUCHI UNIVERSITY DEPARTMENT : BIOLOGICAL CHEMISTRY, FACULTY OF AGRICULTURE, 農学部, 助教授 (30174741)
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| Co-Investigator(Kenkyū-buntansha) |
YAMADA Yasue YAMAGUCHI UNIVERSITY DEPARTMENT : PHARMACOLOGY, SCHOOL OF MEDICINE, 医学部, 助手 (00166737)
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| Project Period (FY) |
1992 – 1993
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| Keywords | Glucose dehydrogenase / gcd gene / cAMP-CRP / Fnr / Phosphotransferase system / PTS |
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| Research Abstract |
Several bacteria including Escherichia coli have two glucose uptake pathways. One is a glucose dehydrogenase-linked gluconate transport system in which glucose is directly oxidized in the periplasm and the produced electrons are transferred to the respiratory chain to form electrochemical gradients across the cytoplasmic membrane. The other is a phosphotransferase system by which glucose is phosphorylated and concomitantly transferred into the cytoplasm. In this study, we investigated to clarify thje physiological roles of the two systems in the different growth phases in E.coli.
The results are summarized as follows. 1) Analysis of the gcd gene encoding glucose dehydrogenase and the topological structure of the product revealed that the protein possesses 5 membrane-spanning segments at the N-terminus and the C-terminal 5/6 portion in the periplasm which catalyzes glucose oxidation. 2) the gcd gene is regulated negatively by cAMP-CRP and Fnr.Especially, the binding of two Fnr proteins t
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o different sites leads DNA bending to repress the transcription. 3) The binding sites of these two factors were determined by site-specific mutagenesis. 4) Gene-disrupted mutant of the gcd gene was constructed to define roles of glucose dehydrogenase for the E.coli growth. The gcd mutant was clearly grown slower than the wild type. The growth was also compared with those of pts^- and gcd^-pts^-. The results suggested that glucose dehydrogenase promote the E.coli growth.
On the basis of the facts that the component genes of PTS are regulated positively by cAMP-CRP, and the intracellular concentration of cAMP is low at the early growth phase and high at the late growth phase, it is likely that the GDH system is expressed at the early growth phase and form electrochemical gradients requred for import of nutrients and synthesis of macromolecules such proteins. On the other hand, the PTS system seems to be expressed at the late growth phase to perform the rational metabolizm of glucose. Thus, the both systems may share the role of the glucose metabolizm during the E.coli growth. Less
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