| Project/Area Number |
08044212
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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| Research Field |
Functional biochemistry
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
MIHARA Katsuyoshi Graduate School of Medical Science, Professor, 大学院・医学系研究科, 教授 (40029963)
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| Co-Investigator(Kenkyū-buntansha) |
WATERNAB Mic バンダビルト大学, 医学部, 教授
SCHATZ Gottfried University of Basel, Biocenter, Professor, バイオセンター, 教授
KOMIYA Tohru Graduate School of Medical Science, Research Associate, 大学院・医学系研究科, 助手 (40304802)
NAKAMURA Nobuhiro Graduate School of Medical Science, Research Associate, 大学院・医学系研究科, 助手 (50294955)
SAKAGUCHI Masao Graduate School of Medical Science, Associate Professor, 大学院・医学系研究科, 助教授 (30205736)
WATERMAN Michael R. Vanderbilt University, School of Medicine, Professor
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| Project Period (FY) |
1996 – 1998
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| Keywords | chaperones / mitochondria / precursor proteins / protein import / membrane translocation / organelles / import receptor |
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| Research Abstract |
Mitochondrial precursor proteins with basic targeting signals may be transported across the outer membrane by sequential binding to acidic receptor sites of increasing affinity. To test this "acid chain" hypothesis, we assayed the interaction of mitochondrial precursors with three acidic receptor domains : the cytosolic domain of the outer membrane receptor Tom2O ; the intermembrane space domain of the outer membrane receptor Tom22 ; and the intermembrane space domain of Tim23, a subunit of the protein import system in the inner membrane. The domains were recombinantly produced, water-soluble and pure proteins. The apparent affinity and salt-resistance of precursor binding increased in the order Tom2O < Tom22 (internal) < Tim23. Precursor binding to the three acidic receptor domains as well as to the pure cytosolic domain of the outer membrane receptor Tom7O was inhibited by excess targeting peptide, but not by an equally basic control peptide. In this membrane-free and defined system, a precursor pre-bound to either the Tom7O or Tom2O domain was efficiently transferred to the Tim23 domain. Transfer was stimulated by the internal Tom22 domain and was much less efficient in the reverse direction. Precursors destined for the outer membrane bound only to Tom2O, but not to the internal Tom22- or the Tim23 domain, and a precursor destined to be inserted into the inner membrane bound only to the Tom2O- and the internal Tom22 domain, but not to the Tim23 domain. These results suggest that specific and sequential binding of a targeting signal to strategically situated acidic receptors along the import pathway delivers a precursor across the outer membrane and also contributes to the intramitochondrial sorting of imported proteins.
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