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YspC: a unique translocator exhibits structural alteration in the complex form with chaperone SycB
Abhishek Basu1, Rakesh Chatterjee, Saumen Datta
1Structural Biology and Bioinformatics Division, Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Kolkata 700032, West Bengal, India.
Yersinia secretion protein C (YspC) is a unique translocator that deviates from other minor translocators. Its structure and interaction with chaperone SycB reveal distinct functional properties within the type three secretion system.
Area of Science:
- Microbiology
- Structural Biology
- Protein Biochemistry
Background:
- Yersinia secretion protein C (YspC) is a component of the Yersinia type three secretion system (T3SS) in Yersinia enterocolitica.
- YspC functions as a translocator, facilitating the transport of effector proteins across bacterial membranes.
- It forms a complex with its cognate chaperone, SycB.
Purpose of the Study:
- To investigate the unique structural and biochemical properties of YspC.
- To elucidate the interaction mechanism between YspC and its chaperone SycB.
- To understand how these interactions influence the function of the Yersinia T3SS translocator.
Main Methods:
- Size exclusion chromatography to determine YspC's oligomeric state.
- Bioinformatic analysis (Multiple sequence alignment, ConSurf) to assess evolutionary deviation.
- Circular dichroism (CD) spectroscopy (near-UV and far-UV) to analyze tertiary and secondary structures.
- Thermal denaturation and trypsinolysis to study protein stability and conformational changes.
- Förster resonance energy transfer (FRET) and interaction studies with truncated SycB forms to map binding interfaces.
Main Results:
- YspC exists predominantly as a monomer and is highly soluble despite a transmembrane region, distinguishing it from other translocators.
- Structural analyses (CD, thermal denaturation, trypsinolysis) reveal unique tertiary and secondary structures of YspC, which are altered upon complex formation with SycB.
- SycB's tetratricopeptide repeat (TPR) regions are masked in the YspC-SycB complex, and interactions with truncated SycB forms indicate altered physiological states of the resulting complexes.
Conclusions:
- YspC represents a novel class of translocator proteins with unique structural and biochemical characteristics.
- The interaction with SycB significantly modulates YspC's structure and stability, suggesting a regulatory role for the chaperone.
- Understanding these molecular details provides insights into the mechanism of Yersinia T3SS assembly and function.
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