The Type III Secretion Translocation Pore Senses Host Cell Contact

Area of Science:

• Microbiology
• Molecular Biology
• Cellular Biology

Background:

• Type III secretion systems (T3SS) are essential virulence factors in many Gram-negative pathogens.
• T3SS deliver effector proteins directly into host cells via a translocon pore.
• The assembly and function of the T3SS translocon pore remain poorly understood.

Purpose of the Study:

• To identify critical protein-protein interactions within the T3SS translocon.
• To elucidate the mechanism of host cell contact sensing by the T3SS.
• To determine the role of the translocator proteins in signal transduction.

Main Methods:

• Utilized a genetic technique to map protein-protein contacts.
• Investigated interactions between translocator proteins (e.g., PopD) and the T3SS needle tip.
• Analyzed translocon function in mutant strains with disrupted protein contacts.

Main Results:

• Identified key contacts essential for translocon function and pore assembly.
• Established the orientation of translocator proteins within the host cell membrane.
• Demonstrated that PopD interaction with the needle tip is crucial for host cell contact sensing.
• Showed that pore conformation changes are involved in detecting host cell contact.

Conclusions:

• The translocation pore actively participates in sensing host cell contact.
• A signal transduction pathway is initiated by pore conformational changes.
• Specific interactions between the pore and T3SS needle tip transmit the signal.