Molecular Model of a Type III Secretion System Needle: Implications for Host-Cell Sensing

Type III secretion systems are essential virulence determinants for many Gram-negative bacterial pathogens. The type III secretion system consists of cytoplasmic, transmembrane, and extracellular domains. The extracellular domain is a hollow needle protruding above the bacterial surface and is held...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2006-08, Vol.103 (33), p.12529-12533
Main Authors: Deane, Janet E., Roversi, Pietro, Cordes, Frank S., Johnson, Steven, Kenjale, Roma, Daniell, Sarah, Booy, Frank, Picking, William D., Picking, Wendy L., Blocker, Ariel J., Lea, Susan M.
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Architecture
Bacteria
Bacterial Proteins - chemistry
Bacterial Proteins - genetics
Bacterial Proteins - metabolism
Biological Sciences
Cell Surface Extensions - chemistry
Cell Surface Extensions - metabolism
Cellular biology
Crystal structure
Crystallography, X-Ray
Lead
Membranes
Models, Molecular
Molecular Sequence Data
Molecules
Monomers
Protein Structure, Tertiary
Protein Subunits - chemistry
Protein Subunits - genetics
Protein Subunits - metabolism
Proteins
Secretion
Shigella
Shigella flexneri
Shigella flexneri - pathogenicity
Virulence
Yersinia
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Summary:Type III secretion systems are essential virulence determinants for many Gram-negative bacterial pathogens. The type III secretion system consists of cytoplasmic, transmembrane, and extracellular domains. The extracellular domain is a hollow needle protruding above the bacterial surface and is held within a basal body that traverses both bacterial membranes. Effector proteins are translocated, via this external needle, directly into host cells, where they subvert normal cell functions to aid infection. Physical contact with host cells initiates secretion and leads to formation of a pore, thought to be contiguous with the needle channel, in the host-cell membrane. Here, we report the crystal structure of the Shigella flexneri needle subunit MxiH and a complete model for the needle assembly built into our three-dimensional EM reconstruction. The model, combined with mutagenesis data, reveals that signaling of host-cell contact is relayed through the needle via intersubunit contacts and suggests a mode of binding for a tip complex.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0602689103