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Direct interaction of a chaperone-bound type III secretion substrate with the export gate
Dominic Gilzer1, Madeleine Schreiner1, Hartmut H Niemann2
1Department of Chemistry, Bielefeld University, Universitaetstrasse 25, 33615, Bielefeld, Germany.
Nature Communications
|June 2, 2022
Summary
Bacterial type III secretion systems (T3SS) use the export gate protein YscV to bind substrate complexes like YscX:YscY. Structural analysis reveals how YscX interacts with YscV, crucial for forming a functional T3SS for effector protein delivery.
Area of Science:
- Microbiology
- Structural Biology
- Molecular Biology
Background:
- Type III secretion systems (T3SS) are essential virulence factors in many gram-negative bacteria.
- T3SS mediate the direct injection of effector proteins into host cells.
- The export gate complex, including SctV (YscV), plays a critical role in substrate translocation.
Purpose of the Study:
- To elucidate the structural basis of substrate recognition and binding to the T3SS export gate.
- To understand the interaction between the YscX:YscY substrate complex and the YscV export gate in Yersinia.
Main Methods:
- X-ray crystallography was used to determine the structures of the YscX:YscY complex alone and in complex with nonameric YscV.
- Structural analysis focused on identifying binding sites and interaction interfaces.
Main Results:
- The YscX:YscY complex binds to YscV at distinct sites.
- The N-terminus of YscX interacts with a YscV binding site shared with flagellar chaperones, indicating a role in substrate recognition.
- The C-terminus of YscX inserts into the YscV ring, interacting with protomers and the stalk protein binding site.
Conclusions:
- The YscV-YscX interaction is essential for assembling a functional, secretion-competent T3SS.
- Structural insights reveal a conserved mechanism for substrate recognition and translocation in T3SS.
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