1993 Fiscal Year Final Research Report Summary
Mechanism of Integration of Proteins into Biomembranes.
| Project/Area Number |
03404071
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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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 | KYUSHU UNIVERSITY |
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Principal Investigator |
OMURA Tsuneo Kyushu University, Graduaet School of Medical Science, Professor, 大学院・医学系研究科, 教授 (80029933)
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| Co-Investigator(Kenkyū-buntansha) |
SAKAGUCHI Masao Kyushu University, Graduaet School of Medical Science, Research Associate, 大学院・医学系研究科, 助手 (30205736)
MORIHASHI Ken-ichirou Kyushu University, Graduaet School of Medical Science, Research Associate, 大学院・医学系研究科, 助手 (30183114)
MIHARA Katsuyoshi Kyushu University, Graduaet School of Medical Science, Associate Professor, 大学院・医学系研究科, 助教授 (40029963)
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| Project Period (FY) |
1991 – 1993
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| Keywords | Membrane proteins / Biomembranes / Membrane topologie / Membrane biogenesis |
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| Research Abstract |
The mechanism of Integration of protein molecules into endoplasmic reticulum (ER) membrane and mitochondiral (Mt) outer membrane was studied with cell-free systems and cultured cells. The import of precursor proteins into mitochondria was also studied with the cell-free system. The following results were obtained.
1. The orientation of the signal-anchor sequence at the amino-terminus in the ER membrane depends on the balance between the amino-terminal charge and the length of the following stretch of hydrophobic amino acids. It was confirmed that the amino-terminus of the signal-anchor sequence of P-450(arom) is in the luminal side of the ER membrane.
2. A highly conserved proline-rich region is present after the hydrophobic stretch of the signal-anchor sequence of microsomal P-450s. The proline-rich region was essential for the formation of the correct conformation of P-450s.
3. The structural requirements for the interruption of the transfer of growing peptides across the ER membrane were clarified. The function of the stop-transfer sequence mainly depends on the hydrophobic core sequence.
4. The peptide-translocation apparatus of the ER membrane was examined by chemically cross-linking the membrane components with the translocating nascent peptides. A novel 9 kDa membrane protein was identified as a possible component of the translocation apparatus.
5. Liver cytosol was found to stimulate the mitochondrial import of the precursor proteins synthesized by the wheat germ lysate translation system. A novel import-stimulating factor was purified from the cytosol. It was a molecular chaperon which holds the precursor proteins in the import-competent forms.
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