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Proc Natl Acad Sci U S A. 2014 Aug 12;111(32):11804-9. doi: 10.1073/pnas.1404506111. Epub 2014 Jul 25.

Native structure of a type IV secretion system core complex essential for Legionella pathogenesis.

Author information

1
Laboratory of Combined Research on Microbiology and Immunology, Research Institute for Microbial Diseases, Osaka University, Yamadaoka 3-1, Suita, Osaka 565-0871, Japan; and.
2
Faculty of Life and Environmental Sciences, Prefectural University of Hiroshima, Shobara, Hiroshima 727-0023, Japan.
3
Laboratory of Combined Research on Microbiology and Immunology, Research Institute for Microbial Diseases, Osaka University, Yamadaoka 3-1, Suita, Osaka 565-0871, Japan; and hnagai@biken.osaka-u.ac.jp.

Abstract

Bacterial type IV secretion systems are evolutionarily related to conjugation systems and play a pivotal role in infection by delivering numerous virulence factors into host cells. Using transmission electron microscopy, we report the native molecular structure of the core complex of the Dot/Icm type IV secretion system encoded by Legionella pneumophila, an intracellular human pathogen. The biochemically isolated core complex, composed of at least five proteins--DotC, DotD, DotF, DotG, and DotH--has a ring-shaped structure. Intriguingly, morphologically distinct premature complexes are formed in the absence of DotG or DotF. Our data suggest that DotG forms a central channel spanning inner and outer membranes. DotF, a component dispensable for type IV secretion, plays a role in efficient embedment of DotG into the functional core complex. These results highlight a common scheme for the biogenesis of transport machinery.

KEYWORDS:

assembly pathway; effector translocation; membrane proteins; nanomachine

PMID:
25062693
PMCID:
PMC4136560
DOI:
10.1073/pnas.1404506111
[Indexed for MEDLINE]
Free PMC Article

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