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

The flagellar motor of Vibrio alginolyticus is made of two parts: a stator consisting of proteins PomA and PomB, and a rotor whose main component is FliG. The interaction between FliG and PomA generates torque for flagellar rotation. Based on cross-linking experiments of double-Cys mutants of PomB, we previously proposed that a conformational change in the periplasmic region of PomB caused stator activation. Double-Cys mutants lost their motility due to an intramolecular disulfide bridge. In this study, we found that the addition of serine, a chemotactic attractant, to a PomB(L160C/I186C) mutant restored motility without cleaving the disulfide bridge. We speculate that serine changed the rotor (FliG) conformation, affecting rotational direction. Combined with the counterclockwise (CCW)-biased mutation FliG(G214S), motility of PomB(L160C/I186C) was restored without the addition of serine. Likewise, motility was restored without serine in Che(-) mutants, in either a CCW-locked or clockwise (CW)-locked strain. In contrast, in a ΔcheY (CCW-locked) strain, Vibrio (L160C/I186C) required serine to be rescued. We speculate that CheY affects stator conformation and motility restoration by serine is independent on the chemotaxis signaling pathway. © 2016 Molecular Biology Society of Japan and John Wiley & Sons Australia, Ltd.

Citation

Tatsuro Nishikino, Shiwei Zhu, Norihiro Takekawa, Seiji Kojima, Yasuhiro Onoue, Michio Homma. Serine suppresses the motor function of a periplasmic PomB mutation in the Vibrio flagella stator. Genes to cells : devoted to molecular & cellular mechanisms. 2016 May;21(5):505-16

PMID: 27004994

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