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Salmonella type III secretion-associated chaperones confer secretion-pathway specificity
1Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06536, USA.
Molecular Microbiology
|February 6, 2004
Summary
Type III secretion systems (TTSSs) use specific domains for protein export. Removing chaperone-binding domains redirects proteins to the flagellar export pathway, revealing an ancestral signal.
Area of Science:
- Bacteriology
- Molecular Biology
- Microbial Pathogenesis
Background:
- Type III protein secretion systems (TTSSs) are crucial for bacterial virulence and share ancestry with flagellar export systems.
- TTSS-secreted proteins typically have two targeting domains: an N-terminal signal and a chaperone-binding domain.
Purpose of the Study:
- To investigate the roles of N-terminal and chaperone-binding domains in TTSS protein secretion and pathway specificity.
- To determine if secretion signals can function independently.
Main Methods:
- Mutational analysis of Salmonella typhimurium TTSS-secreted proteins (SptP, SopE) to delete chaperone-binding domains.
- Assessing protein secretion via TTSS and flagellar export pathways.
- Evaluating protein translocation into host cells.
Main Results:
- Deletion of chaperone-binding domains caused SptP and SopE to be secreted via the flagellar pathway, not TTSS.
- An ancestral flagellar secretion signal is present in TTSS proteins, revealed upon chaperone-binding domain removal.
- Both N-terminal and chaperone-binding domains are essential for TTSS-mediated secretion and host cell translocation.
Conclusions:
- TTSS-associated chaperones confer secretion-pathway specificity to their cognate proteins.
- The chaperone-binding domain is critical for directing proteins to the TTSS pathway, masking an ancestral flagellar signal.