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Serine suppresses the motor function of a periplasmic PomB mutation in the Vibrio flagella stator

Tatsuro Nishikino1, Shiwei Zhu1, Norihiro Takekawa1

  • 1Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, 464-8602, Japan.

Genes to Cells : Devoted to Molecular & Cellular Mechanisms
|March 24, 2016
PubMed

Insights

Serine, a chemotactic attractant, restores motility in Vibrio alginolyticus flagellar motor mutants by influencing rotor conformation, independent of the chemotaxis signaling pathway. This finding sheds light on flagellar motor regulation.

Area of Science:

  • Microbiology
  • Biochemistry
  • Molecular Biology

Background:

  • The Vibrio alginolyticus flagellar motor comprises a stator (PomA/PomB) and rotor (FliG).
  • Previous studies suggested stator activation via periplasmic PomB conformational changes.
  • Mutations creating disulfide bridges in PomB abolish motility.

Purpose of the Study:

  • To investigate the mechanism of motility restoration in PomB mutants by serine.
  • To elucidate the role of the chemotaxis signaling pathway in flagellar motor regulation.

Main Methods:

  • Site-directed mutagenesis to create PomB double-Cys mutants (L160C/I186C).
  • Assessment of bacterial motility in the presence and absence of serine.
  • Analysis of motility in conjunction with specific flagellar motor mutations (FliG(G214S)) and chemotaxis gene deletions (Che(-), ΔcheY).

Main Results:

  • Serine restored motility in PomB(L160C/I186C) mutants without disulfide bond cleavage.
  • Motility restoration by serine was observed in various genetic backgrounds, including CCW-biased and CW-locked strains.
  • However, a ΔcheY (CCW-locked) strain required serine for motility rescue, suggesting a complex interaction.

Conclusions:

  • Serine may restore motility by inducing conformational changes in the rotor (FliG), influencing rotational direction.
  • The chemotaxis protein CheY appears to influence stator conformation.
  • Motility restoration by serine is largely independent of the canonical chemotaxis signaling pathway, but CheY plays a role.

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