Bcr4 Is a Chaperone for the Inner Rod Protein in the Bordetella Type III Secretion System
Masataka Goto1, Akio Abe1, Tomoko Hanawa2
1Laboratory of Bacterial Infection, Graduate School of Infection Control Sciences, Kitasato Universitygrid.410786.c, Tokyo, Japan.
Microbiology Spectrum
|August 30, 2022
Summary
Bordetella bronchiseptica's Bcr4 protein stabilizes the BscI component of the type III secretion system (T3SS). This stabilization is crucial for constructing the T3SS machinery and injecting virulence proteins into host cells.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- Bordetella bronchiseptica utilizes a type III secretion system (T3SS) to deliver effector proteins into host cells.
- Chaperone proteins are known to stabilize components of the T3SS machinery.
- A previously identified protein, Bcr4, was suggested to be a chaperone-like protein regulating T3SS activity in B. bronchiseptica.
Purpose of the Study:
- To elucidate the mechanism by which Bcr4 controls T3SS activity in B. bronchiseptica.
- To determine the interaction partners and functional role of Bcr4 in T3SS assembly and function.
Main Methods:
- Pulldown assays were employed to identify Bcr4 interaction partners.
- Truncated Bcr4 derivatives were used to map functional domains involved in BscI interaction.
- Secretion profiles and effector translocation assays were performed on B. bronchiseptica strains with altered Bcr4 and BscI expression.
Main Results:
- Bcr4 was found to interact with BscI, an inner rod protein component of the T3SS.
- The C-terminal region of Bcr4 is essential for BscI interaction and T3SS activation.
- Deletion of BscI abolished type III secretion and effector translocation, while Bcr4 was shown to stabilize BscI.
Conclusions:
- Bcr4 acts as a chaperone for the T3SS inner rod protein BscI, stabilizing it for proper T3SS machinery assembly.
- This stabilization by Bcr4 is critical for the functional construction of the T3SS in B. bronchiseptica.
- This study represents the first identification of a chaperone for a T3SS inner rod protein in virulence bacteria.
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