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A putative spermidine synthase interacts with flagellar switch protein FliM and regulates motility in Helicobacter

Huawei Zhang1, Kwok Ho Lam1, Wendy Wai Ling Lam1

  • 1Centre for Protein Science and Crystallography, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong.

Molecular Microbiology
|September 5, 2017
PubMed

Insights

Spermidine synthase SpeE interacts with the flagellar switch protein FliM in Helicobacter pylori, altering motor rotation. This interaction, unique to Helicobacter, impacts bacterial virulence and motility.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • The bacterial flagellar motor is crucial for motility and virulence.
  • Proteins outside flagellar and chemotaxis systems can modulate motor function.
  • The precise mechanisms of these modulations are not fully understood.

Purpose of the Study:

  • To identify novel regulators of flagellar motor function in Helicobacter pylori.
  • To investigate the role of spermidine synthase (SpeE) in flagellar motility.
  • To elucidate the structural basis of the SpeE-FliM interaction.

Main Methods:

  • Pull-down assay and mass spectrometry to identify interacting proteins.
  • Generation and analysis of a speE-null mutant for motility assessment.
  • X-ray crystallography to determine the structure of the FliM-SpeE complex.

Main Results:

  • Spermidine synthase (SpeE) was identified as a FliM interacting partner.
  • SpeE deletion resulted in clockwise rotation bias without affecting flagellar formation.
  • Crystal structure revealed SpeE dimer binding to FliM's middle domain, overlapping with FliG interaction sites.
  • FliM-SpeE association appears unique to Helicobacter species.

Conclusions:

  • SpeE modulates Helicobacter pylori flagellar motor function by interacting with FliM.
  • This interaction influences the direction of flagellar rotation, impacting bacterial motility.
  • The FliM-SpeE interaction is a species-specific mechanism potentially contributing to Helicobacter pathogenesis.

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