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Role of the cytoplasmic C terminus of the FliF motor protein in flagellar assembly and rotation

Grunenfelder, B. and Gehrig, S. and Jenal, U.. (2003) Role of the cytoplasmic C terminus of the FliF motor protein in flagellar assembly and rotation. Journal of bacteriology, Vol. 185, H. 5. pp. 1624-1633.

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Official URL: http://edoc.unibas.ch/dok/A5258558

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Abstract

Twenty-six FliF monomers assemble into the MS ring, a central motor component of the bacterial flagellum that anchors the structure in the inner membrane. Approximately 100 amino acids at the C terminus of FliF are exposed to the cytoplasm and, through the interaction with the FliG switch protein, a component of the flagellar C ring, are essential for the assembly of the motor. In this study, we have dissected the entire cytoplasmic C terminus of the Caulobacter crescentus FliF protein by high-resolution mutational analysis and studied the mutant forms with regard to the assembly, checkpoint control, and function of the flagellum. Only nine amino acids at the very C terminus of FliF are essential for flagellar assembly. Deletion or substitution of about 10 amino acids preceding the very C terminus of FliF resulted in assembly-competent but nonfunctional flagella, making these the first fliF mutations described so far with a Fla(+) but Mot(-) phenotype. Removal of about 20 amino acids further upstream resulted in functional flagella, but cells carrying these mutations were not able to spread efficiently on semisolid agar plates. At least 61 amino acids located between the functionally relevant C terminus and the second membrane-spanning domain of FliF were not required for flagellar assembly and performance. A strict correlation was found between the ability of FliF mutant versions to assemble into a flagellum, flagellar class III gene expression, and a block in cell division. Motile suppressors could be isolated for nonmotile mutants but not for mutants lacking a flagellum. Several of these suppressor mutations were localized to the 5' region of the fliG gene. These results provide genetic support for a model in which only a short stretch of amino acids at the immediate C terminus of FliF is required for flagellar assembly through stable interaction with the FliG switch protein.
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Infection Biology > Molecular Microbiology (Jenal)
05 Faculty of Science > Departement Biozentrum > Growth & Development > Molecular Microbiology (Jenal)
UniBasel Contributors:Jenal, Urs
Item Type:Article, refereed
Article Subtype:Research Article
Bibsysno:Link to catalogue
Publisher:American Society for Microbiology
ISSN:1098-5530
Note:Publication type according to Uni Basel Research Database: Journal article
Last Modified:22 Mar 2012 14:20
Deposited On:22 Mar 2012 13:20

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