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Function of the conserved FHIPEP domain of the flagellar type III export apparatus, protein FlhA

Clive S Barker1, Tomoharu Inoue1, Irina V Meshcheryakova1

  • 1Trans-membrane Trafficking Unit, Okinawa Institute of Science and Technology, Okinawa, Japan.

Molecular Microbiology
|December 23, 2015
PubMed

Insights

Mutagenizing the FHIPEP region of bacterial flagellar protein export protein FlhA disrupted flagellar assembly. This region acts as a gate, controlling substrate entry into the export pore and essential for bacterial motility.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Bacterial Physiology

Background:

  • The Type III flagellar protein export apparatus is crucial for bacterial motility.
  • FlhA is a key membrane protein in this apparatus, homologous to FHIPEP export proteins.
  • FHIPEP proteins possess a conserved cytoplasmic domain.

Purpose of the Study:

  • To investigate the role of the conserved FHIPEP region within Salmonella FlhA.
  • To determine how mutations in this region affect flagellar protein export and bacterial motility.

Main Methods:

  • Site-directed mutagenesis of the cloned Salmonella flhA gene, focusing on the FHIPEP region.
  • Analysis of bacterial motility and flagellar structure via microscopy.
  • Western blot hybridization to assess protein export.

Main Results:

  • Most FlhA FHIPEP mutants resulted in loss of motility and flagella, with no detectable export of hook protein and flagellin.
  • A D199A mutant produced short flagella, while a V151L mutant showed no flagella and excreted un-polymerized hook protein.
  • A suppressor mutation in FlhB partially restored flagellar export and assembly.

Conclusions:

  • The FHIPEP region of FlhA is critical for regulating substrate entry into the bacterial flagellar protein export apparatus.
  • This region likely functions as a gate, controlling the flow of proteins through the export pore.
  • Mutations in the FHIPEP region severely impair flagellar biogenesis and bacterial motility.

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