2019 Fiscal Year Final Research Report
Structural and Functional Study of Binary Toxin Translocon by Cryo-EM and X-ray Crystallography
Project/Area Number |
18K06170
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Research Category |
Grant-in-Aid for Scientific Research (C)
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Allocation Type | Multi-year Fund |
Section | 一般 |
Review Section |
Basic Section 43040:Biophysics-related
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Research Institution | Kyoto Sangyo University |
Principal Investigator |
TSUGE Hideaki 京都産業大学, 生命科学部, 教授 (40299342)
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Co-Investigator(Kenkyū-buntansha) |
吉田 徹 京都産業大学, 総合生命科学部, 研究員 (30724546)
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Project Period (FY) |
2018-04-01 – 2020-03-31
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Keywords | ウェルシュ菌 / 二成分毒素 / タンパク質膜透過 / ADPリボシル化 / ディフィシル菌 / クライオ電子顕微鏡 / 単粒子解析 / 超分子複合体 |
Outline of Final Research Achievements |
The iota toxin produced by Clostridium perfringens type E is a binary toxin comprising two independent polypeptides: Ia, an ADP-ribosyltransferase, and Ib, which is involved in cell binding and translocation of Ia across the cell membrane. Here we report cryo-EM structures of the translocation channel Ib-pore and its complex with Ia. The high-resolution Ib-pore structure demonstrates a similar structural framework to that of the catalytic phi-clamp of the anthrax protective antigen pore. However, the Ia-bound Ib-pore structure shows a unique binding mode of Ia: one Ia binds to the Ib-pore, and the Ia amino-terminal domain forms multiple weak interactions with two additional Ib-pore constriction sites. Furthermore, Ib-binding induces tilting and partial unfolding of the Ia N-terminal α-helix, permitting its extension to the phi-clamp gate. This new mechanism of N-terminal unfolding is crucial for protein translocation.
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Free Research Field |
構造生物学、生物物理学、生化学、細菌学、タンパク質科学
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Academic Significance and Societal Importance of the Research Achievements |
ウェルシュ菌の二成分毒素はアクチンをADPリボシル化する酵素成分のIaと、Iaを膜を介して細胞内に透過させる膜結合成分Ibからなる。Ibは中央に孔を持つIb膜孔を形成し、Iaがこの中を通過する。この二成分毒素複合体の構造を明らかにした。このことより、タンパク質膜透過の仕組みの一端を明らかにした。似た二成分毒素はディフィシル菌(ヒト感染症)や炭疽菌でもみられ、膜孔の阻害剤創薬の重要な知見となる。
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