Chaperone-subunit-usher interactions required for donor strand exchange during bacterial pilus assembly

Area of Science:

• Microbiology
• Structural Biology
• Biochemistry

Background:

• Type 1 pili are crucial virulence factors for uropathogenic Escherichia coli (UPEC).
• Pilus assembly occurs through the chaperone-usher pathway, involving specific protein interactions and translocation across the outer membrane.
• Understanding this pathway is vital for developing targeted antimicrobial strategies.

Purpose of the Study:

• To elucidate the molecular mechanisms of the donor strand exchange assembly in type 1 pilus biogenesis.
• To identify the specific protein components and their functions in targeting and assembly at the usher.

Main Methods:

• Investigated the role of FimH and chaperone proteins in targeting and assembly.
• Analyzed the donor strand exchange mechanism during pilus formation.
• Examined the necessity of donor strand exchange for subunit translocation.

Main Results:

• Targeting of the FimC-FimH complex to the usher is primarily mediated by FimH.
• A previously unrecognized chaperone function is essential for subunit participation in donor strand exchange.
• Donor strand exchange is critical for subunit translocation across the outer membrane usher.

Conclusions:

• FimH plays a key role in initiating pilus biogenesis by targeting the chaperone-subunit complex to the usher.
• The chaperone possesses a novel function crucial for the donor strand exchange mechanism.
• The donor strand exchange process is indispensable for the translocation of subunits through the usher, enabling pilus assembly.