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Proc Natl Acad Sci U S A. 2013 Aug 27;110(35):14390-5. doi: 10.1073/pnas.1308306110. Epub 2013 Aug 12.

Cryoelectron tomography reveals the sequential assembly of bacterial flagella in Borrelia burgdorferi.

Author information

1
Department of Pathology and Laboratory Medicine, University of Texas Health Science Center, Houston, TX 77030, USA.

Abstract

Periplasmic flagella are essential for the distinctive morphology, motility, and infectious life cycle of the Lyme disease spirochete Borrelia burgdorferi. In this study, we genetically trapped intermediates in flagellar assembly and determined the 3D structures of the intermediates to 4-nm resolution by cryoelectron tomography. We provide structural evidence that secretion of rod substrates triggers remodeling of the central channel in the flagellar secretion apparatus from a closed to an open conformation. This open channel then serves as both a gateway and a template for flagellar rod assembly. The individual proteins assemble sequentially to form a modular rod. The hook cap initiates hook assembly on completion of the rod, and the filament cap facilitates filament assembly after formation of the mature hook. Cryoelectron tomography and mutational analysis thus combine synergistically to provide a unique structural blueprint of the assembly process of this intricate molecular machine in intact cells.

KEYWORDS:

bacterial motility; macromolecular assemblages; molecular machines; protein secretion

PMID:
23940315
PMCID:
PMC3761569
DOI:
10.1073/pnas.1308306110
[Indexed for MEDLINE]
Free PMC Article

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