Structural basis of the flagellar axial structure and its construction

2023 Fiscal Year Final Research Report

• Project/Area Number: 21H02443
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 43040:Biophysics-related
• Research Institution: Osaka University
• Principal Investigator: Imada Katsumi 大阪大学, 大学院理学研究科, 教授 (40346143)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 細菌べん毛 / クライオ電子顕微鏡 / X線結晶構造 / シンメトリーミスマッチ / 超分子複合体

Outline of Final Research Achievements

The axial structure of the bacterial flagellum, an organelle responsible for bacterial motility, is a protein assembly composed of a rigid rod, a flexible hook, and a filament that is highly rigid yet capable of superhelical transition. The mechanisms behind the formation of such a complex structure and the integration of the parts, which vary in physical properties, functions, structures, and symmetries, remain unclear. In this study, we analyzed the structures of the intermediate states of flagellar formation and the structures of short filament mutants using cryo-electron microscopy. Through this analysis, we elucidated the mechanisms of hook and filament growth, as well as the molecular mechanism how the hook and filament are connected.

Free Research Field

生物物理学・構造生物学

Academic Significance and Societal Importance of the Research Achievements

生命活動を担う複雑な生体分子超複合体の多くは、シンメトリーミスマッチを利用して作られ作動する。本研究で解明されたべん毛軸構造の構築のしくみは、他の生体超分子複合体の構築・作動原理を理解する上で重要な知見であり、さらには、ナノスケールでの力学研究やナノマシン設計に向けて重要な基盤となる。また、べん毛軸構造形成阻害をターゲットとして細菌運動性を奪うことで感染を阻止する新しいタイプの薬剤開発の構造基盤となる。