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Elife. 2016 Sep 24;5. pii: e18857. doi: 10.7554/eLife.18857.

Bacterial flagellar capping proteins adopt diverse oligomeric states.

Author information

1
Institute of Human Virology, University of Maryland School of Medicine, Baltimore, United States.
2
Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, United States.
3
Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, United States.
4
Department of Biology, University of Konstanz, Konstanz, Germany.
5
Department of Biotechnology, Institute of Biochemistry, Biotechnology and Bioinformatics, Technische Universität Braunschweig, Braunschweig, Germany.
6
Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem, Israel.
7
Department of Chemistry and Biochemistry, University of Maryland College Park, Baltimore, United States.
8
Department of Medicine, University of Maryland School of Medicine, Baltimore, United States.
9
Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, United States.

Abstract

Flagella are crucial for bacterial motility and pathogenesis. The flagellar capping protein (FliD) regulates filament assembly by chaperoning and sorting flagellin (FliC) proteins after they traverse the hollow filament and exit the growing flagellum tip. In the absence of FliD, flagella are not formed, resulting in impaired motility and infectivity. Here, we report the 2.2 Å resolution X-ray crystal structure of FliD from Pseudomonas aeruginosa, the first high-resolution structure of any FliD protein from any bacterium. Using this evidence in combination with a multitude of biophysical and functional analyses, we find that Pseudomonas FliD exhibits unexpected structural similarity to other flagellar proteins at the domain level, adopts a unique hexameric oligomeric state, and depends on flexible determinants for oligomerization. Considering that the flagellin filaments on which FliD oligomers are affixed vary in protofilament number between bacteria, our results suggest that FliD oligomer stoichiometries vary across bacteria to complement their filament assemblies.

KEYWORDS:

Pseudomonas; X-ray crystallography; analytical ultracentrifugation; biophysics; flagella; hydrogen-deuterium exchange; infectious disease; microbiology; structural biology

PMID:
27664419
PMCID:
PMC5072837
DOI:
10.7554/eLife.18857
[Indexed for MEDLINE]
Free PMC Article

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