Structure analysis of the flagellar cap-filament complex by electron cryomicroscopy and single-particle image analysis

Koji Yonekura, Saori Maki-Yonekura, Keiichi Namba

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)

Abstract

The cap of the bacterial flagellum plays an essential role in the growth of the long helical filament by promoting the efficient self-assembly of flagellin transported to the distal end through the narrow central channel of the flagellum. The structure of the cap-filament complex was analyzed by electron cryomicroscopy and single-particle image analysis to understand how the cap stays attached while allowing the flagellin insertion between the cap and the filament end and also allowing the HAP proteins to pass through. In the images of the complex, the projection pattern of the helical subunit array in the filament portion occupied the major fraction but was variable depending on the azimuthal orientation of the filament; therefore the images showed a strong tendency to be misaligned. Various methods had to be newly developed to correctly align the images by overcoming this misalignment problem. The structure thus obtained clearly demonstrated the pentameric structure of the cap and how the cap operates. The new methods of analysis presented here would be generally applicable to cap structures of various filaments that play biologically important roles in cellular activities.

Original languageEnglish
Pages (from-to)246-253
Number of pages8
JournalJournal of Structural Biology
Volume133
Issue number2-3
DOIs
Publication statusPublished - 2001
Externally publishedYes

Keywords

  • Bacterial flagellum
  • Electron cryomicroscopy
  • Flagellar cap
  • Flagellin
  • FliD
  • HAP2
  • Salmonella
  • Self-assembly
  • Single-particle image analysis

ASJC Scopus subject areas

  • Structural Biology

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