Bacterial flagellar capping proteins adopt diverse oligomeric states

Sandra Postel, Daniel Deredge, Daniel A. Bonsor, Xiong Yu, Kay Diederichs, Saskia Helmsing, Aviv Vromen, Assaf Friedler, Michael Hust, Edward H. Egelman, Dorothy Beckett, Patrick L. Wintrode, Eric J. Sundberg

Research output: Contribution to journalArticlepeer-review


Flagella are crucial for bacterial motility and pathogenesis. The flagellar capping protein (FliD) regulates filament assembly by chaperoning and sorting flagellin (FliC) proteins after they traverse the hollow filament and exit the growing flagellum tip. In the absence of FliD, flagella are not formed, resulting in impaired motility and infectivity. Here, we report the 2.2 Å resolution X-ray crystal structure of FliD from Pseudomonas aeruginosa, the first high-resolution structure of any FliD protein from any bacterium. Using this evidence in combination with a multitude of biophysical and functional analyses, we find that Pseudomonas FliD exhibits unexpected structural similarity to other flagellar proteins at the domain level, adopts a unique hexameric oligomeric state, and depends on flexible determinants for oligomerization. Considering that the flagellin filaments on which FliD oligomers are affixed vary in protofilament number between bacteria, our results suggest that FliD oligomer stoichiometries vary across bacteria to complement their filament assemblies.

Original languageAmerican English
Article numbere18857
StatePublished - 24 Sep 2016

All Science Journal Classification (ASJC) codes

  • General Immunology and Microbiology
  • General Biochemistry,Genetics and Molecular Biology
  • General Neuroscience


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