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CsrA-FliW interaction governs flagellin homeostasis and a checkpoint on flagellar morphogenesis in Bacillus subtilis

Sampriti Mukherjee1, Helen Yakhnin, Dave Kysela

  • 1Department of Biology, Indiana University, Bloomington, IN 47408, USA.

Molecular Microbiology
|September 8, 2011
PubMed

Insights

Researchers discovered FliW, a protein that acts as an antagonist to CsrA, controlling flagellin synthesis in Bacillus subtilis through a novel partner-switching mechanism for precise bacterial motility regulation.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Bacterial Genetics

Background:

  • CsrA is a conserved RNA-binding protein regulating gene expression in bacteria.
  • In Gram-negative bacteria, CsrA activity is typically antagonized by small RNAs (sRNAs).
  • A protein-based antagonist for CsrA has not been previously identified.

Purpose of the Study:

  • To identify and characterize novel regulators of CsrA activity.
  • To elucidate the mechanism controlling flagellin synthesis in Bacillus subtilis.
  • To investigate the role of protein-protein interactions in post-transcriptional gene regulation.

Main Methods:

  • Protein-protein interaction studies to identify FliW as a CsrA binder.
  • Genetic analysis in Bacillus subtilis to assess the function of FliW and CsrA in flagellin regulation.
  • Biochemical assays to confirm CsrA binding and activity modulation by FliW.

Main Results:

  • FliW is identified as the first protein antagonist of CsrA activity.
  • FliW acts via a partner-switching mechanism, releasing CsrA-mediated repression of flagellin (Hag) synthesis.
  • This regulation occurs post-hook completion, linking flagellar assembly to flagellin production.
  • Flagellin synthesis is homeostatically autoregulated by this FliW-CsrA interaction.

Conclusions:

  • FliW-mediated antagonism of CsrA provides a novel mechanism for controlling gene expression.
  • Homeostatic autoregulation of structural subunits is a potentially widespread mechanism in bacteria.
  • CsrA's ancestral role in flagellar assembly suggests its evolution towards broader regulatory functions, including virulence.

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