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Updated: Apr 18, 2026
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Use of Shigella flexneri to Study Autophagy-Cytoskeleton Interactions
Published on: September 9, 2014
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Visualization of the type III secretion sorting platform of Shigella flexneri
Bo Hu1, Dustin R Morado1, William Margolin2
1Departments of Pathology and Laboratory Medicine and.
Summary
Researchers visualized the bacterial type III secretion machine
Area of Science:
- Microbiology
- Structural Biology
- Molecular Biology
Background:
- Bacterial type III secretion machines inject virulence proteins into host cells.
- These machines are structurally related to bacterial flagella.
- The cytoplasmic sorting platform is crucial but poorly understood.
Purpose of the Study:
- To determine the high-resolution in situ structure of the intact type III secretion machine.
- To characterize the molecular architecture of the cytoplasmic sorting platform.
- To propose a model for the sorting platform's assembly and function.
Main Methods:
- High-throughput cryoelectron tomography (cryo-ET) was employed.
- Subtomogram averaging was used to determine the in situ structure.
- Molecular modeling of wild-type and mutant machines was performed.
Main Results:
- The cytoplasmic sorting platform comprises a central hub, six spokes, and pod-like structures.
- The hub is mainly composed of the Spa47 ATPase hexamer.
- MxiN protein forms the spokes, and Spa33 protein forms the pods.
Conclusions:
- A detailed molecular model of the type III secretion machine's sorting platform was proposed.
- The structure reveals essential contacts for nanomachine assembly.
- This work highlights key structural differences between type III secretion machines and flagella.
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