Elucidation of mechanisms underlying disulfide bond formation in nascent chains

2019 Fiscal Year Final Research Report

• Project Area: Nascent-chain Biology
• Project/Area Number: 26116005
• Research Category: Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
• Allocation Type: Single-year Grants
• Review Section: Biological Sciences
• Research Institution: Tohoku University
• Principal Investigator: Kenji Inaba 東北大学, 多元物質科学研究所, 教授 (10423039)
• Co-Investigator(Kenkyū-buntansha): 門倉 広 東北大学, 多元物質科学研究所, 准教授 (70224558)
• Project Period (FY): 2014-07-10 – 2019-03-31
• Keywords: タンパク質品質管理 / ジスルフィド結合 / X線結晶構造解析 / 高速原子間力顕微鏡

Outline of Final Research Achievements

Disulfide bond formation is a crucial step in the folding of numerous cell-surface proteins. Here, we developed a system to study the cotranslational folding of a cell-surface multidomain protein, LDL receptor. Using the system, we found that isomerization of nonnative disulfides to native ones, a key step in the folding of many cell-surface proteins, takes place at a specific timing during synthesis in a manner dependent of a downstream region of the polypeptide. Thus, folding of multidomain proteins in the ER may be more coordinated and elaborated than thought. We also succeeded in single-molecule observation of PDI engaged in the catalysis of oxidative protein folding using high-speed atomic force microscopy. Consequently, we discovered that PDI dimerizes in a substrate-dependent manner and catalyzes its oxidative folding in the central cavity of the dimer. These findings provide a number of new insights into the disulfide bond formation system of mammalian cells.

Free Research Field

構造生物学、生化学

Academic Significance and Societal Importance of the Research Achievements

本研究では、リボソーム上で翻訳合成されつつ小胞体に送り込まれてくるLDL受容体の新生鎖にジスルフィド結合が導入される過程の詳細を解明することに初めて成功した。さらに、50年以上もの研究の歴史があるPDI酵素が基質依存的に二量体を形成し、酸化的フォールディングを促進するという、同酵素の全く新しい触媒機構を解明した。ジスルフィド結合形成の仕組みの破綻は糖尿病や高脂血症などの疾患の原因になることから、以上の知見は基礎的に重要であるばかりでなく、ジスルフィド結合の形成不全が引き起こす疾患の発症の機序の解明に役立つと期待される。