Crystallography and electron microscopy of chaperone/usher pilus systems

Area of Science:

• Microbiology
• Structural Biology
• Biochemistry

Background:

• The chaperone-usher (CU) pathway is a conserved system in bacteria for assembling and translocating adhesive protein fibers called pili or fimbriae.
• Pili are crucial for pathogenic bacteria, mediating attachment to host cells via adhesins at their tips, initiating infections like those caused by uropathogenic E. coli (UPEC).

Purpose of the Study:

• To review the structural biology of the chaperone-usher pathway.
• To elucidate the mechanisms underlying the biogenesis of CU pili, a significant class of bacterial organelles.

Main Methods:

• This review synthesizes existing structural data on the chaperone-usher pathway.
• Focuses on the roles of periplasmic chaperones and the outer membrane usher in pilus assembly.

Main Results:

• The usher protein catalyzes the ordered assembly of pilus subunits.
• Chaperones are released, and the growing pilus is translocated stepwise to the bacterial surface.

Conclusions:

• Structural insights into the chaperone-usher pathway reveal the intricate mechanisms of pilus biogenesis.
• Understanding this pathway is key to comprehending bacterial adhesion and infection processes.