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The function of the Na+-driven flagellum of Vibrio cholerae is determined by osmolality and pH.

ABSTRACT: Vibrio cholerae is motile by its polar flagellum, which is driven by a Na(+)-conducting motor. The stators of the motor, composed of four PomA and two PomB subunits, provide access for Na(+) to the torque-generating unit of the motor. To characterize the Na(+) pathway formed by the PomAB complex, we studied the influence of chloride salts (chaotropic, Na(+), and K(+)) and pH on the motility of V. cholerae. Motility decreased at elevated pH but increased if a chaotropic chloride salt was added, which rules out a direct Na(+) and H(+) competition in the process of binding to the conserved PomB D23 residue. Cells expressing the PomB S26A/T or D42N variants lost motility at low Na(+) concentrations but regained motility in the presence of 170 mM chloride. Both PomA and PomB were modified by N,N'-dicyclohexylcarbodiimide (DCCD), indicating the presence of protonated carboxyl groups in the hydrophobic regions of the two proteins. Na(+) did not protect PomA and PomB from this modification. Our study shows that both osmolality and pH have an influence on the function of the flagellum from V. cholerae. We propose that D23, S26, and D42 of PomB are part of an ion-conducting pathway formed by the PomAB stator complex.

SUBMITTER: Halang P

PROVIDER: S-EPMC3807483 | biostudies-literature | 2013 Nov

REPOSITORIES: biostudies-literature

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The function of the Na+-driven flagellum of Vibrio cholerae is determined by osmolality and pH.

Halang Petra P Leptihn Sebastian S Meier Thomas T Vorburger Thomas T Steuber Julia J

Journal of bacteriology 20130823 21

Vibrio cholerae is motile by its polar flagellum, which is driven by a Na(+)-conducting motor. The stators of the motor, composed of four PomA and two PomB subunits, provide access for Na(+) to the torque-generating unit of the motor. To characterize the Na(+) pathway formed by the PomAB complex, we studied the influence of chloride salts (chaotropic, Na(+), and K(+)) and pH on the motility of V. cholerae. Motility decreased at elevated pH but increased if a chaotropic chloride salt was added, w ...[more]

PMID: 23974033

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Project description:Vibrio cholerae is a Gram-negative bacterium with a monotrichous flagellum that causes the human disease cholera. Flagellum-mediated motility is an integral part of the bacterial life cycle inside the host and in the aquatic environment. The V. cholerae flagellar filament is composed of five flagellin subunits (FlaA, FlaB, FlaC, FlaD, and FlaE); however, only FlaA is necessary and sufficient for filament synthesis. flaA is transcribed from a class III flagellar promoter, whereas the other four flagellins are transcribed from class IV promoters. However, expressing flaA from a class IV promoter still facilitated motility in a strain that was otherwise lacking all five flagellins (ΔflaA-E). Furthermore, FlaA from V. parahaemolyticus (FlaAVP; 77% identity) supported motility of the V. cholerae ΔflaA-E strain, whereas FlaA from V. vulnificus (FlaAVV; 75% identity) did not, indicating that FlaA amino acid sequence is responsible for its critical role in flagellar synthesis. Chimeric proteins composed of different domains of FlaAVC and FlaD or FlaAVV revealed that the N-terminal D1 domain (D1N) contains an important region required for FlaA function. Further analyses of chimeric FlaAVC-FlaD proteins identified a lysine residue present at position 145 of the other flagellins but absent from FlaAVC that can prevent monofilament formation. Moreover, the D1N region of amino acids 87 to 153 of FlaAVV inserted into FlaAVC allows monofilament formation but not motility, apparently due to the lack of filament curvature. These results identify residues within the D1N domain that allow FlaAVC to fold into a functional filament structure and suggest that FlaAVC assists correct folding of the other flagellins.IMPORTANCEV. cholerae causes the severe diarrheal disease cholera. Its ability to swim is mediated by rotation of a polar flagellum, and this motility is integral to its ability to cause disease and persist in the environment. The current studies illuminate how one specific flagellin (FlaA) within a multiflagellin structure mediates formation of the flagellar filament, thus allowing V. cholerae to swim. This knowledge can lead to safer vaccines and potential therapeutics to inhibit cholera.

Dataset Information

The function of the Na+-driven flagellum of Vibrio cholerae is determined by osmolality and pH.

Publications

The function of the Na+-driven flagellum of Vibrio cholerae is determined by osmolality and pH.

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