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Bacterial flagellar axial structure and its construction

Abstract

The bacterial flagellum is a motile organelle composed of thousands of protein subunits. The filamentous part that extends from the cell membrane is called the axial structure and consists of three major parts, the filament, hook, and rod, and other minor components. Each of the three main parts shares a similar self-assembly mechanism and a common basic architecture of subunit arrangement while showing quite distinct mechanical properties to achieve its specific function. Structural and molecular mechanisms to produce these various mechanical properties of the axial structure, such as the filament, the hook, and the rod, have been revealed by the complementary use of X-ray crystallography and cryo-electron microscopy. In addition, the mechanism of growth of the axial structure is beginning to be revealed based on the molecular structure.

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Acknowledgements

The author thanks Keiichi Namba and Tohru Minamino for their encouragement and fruitful discussion. This work was partially supported by the Japanese Ministry of Education, Culture, Sports, Science and Technology.

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Correspondence to Katsumi Imada.

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This article is part of a Special Issue on ‘Biomolecules to Bio-nanomachines—Fumio Arisaka 70th Birthday’ edited by Damien Hall, Junichi Takagi and Haruki Nakamura.

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Imada, K. Bacterial flagellar axial structure and its construction. Biophys Rev 10, 559–570 (2018). https://doi.org/10.1007/s12551-017-0378-z

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Keywords

  • Bacterial flagellum
  • Axial structure
  • X-ray crystallography
  • Cryo-electron microscopy