Work

Structural insights into the secretin complex of a type IVb pilus system

Year: 2025

Type: article

Abstract: The bundle-forming pilus (BFP) system in enteropathogenic Escherichia coli (EPEC) produces type IVb pili that enable bacterial auto-aggregation, facilitating bacterial adhesion, colonization, and virulence. One of its components, lipoprotein BfpB, interacts with BfpG to form a secretin channel complex that enables pilus translocation across the outer membrane. Here, we report a high-resolution cryo-EM structure of the BfpB-BfpG complex, revealing a 17:17 stoichiometry with stable zigzag-like interactions between BfpG and BfpB near the N3 ring. Secretin BfpB consists of three β-barrels, including an additional N3 barrel that is crucial for BFP biogenesis. As a lipoprotein-type secretin, BfpB possesses an N-terminal LG domain that bridges the N0 domain and the outer membrane, ensuring its correct localization to the bacterial outer membrane. The C-terminal region of the LG domain mediates binding to BfpG, and disruption of these interactions impairs BFP biogenesis. Our results advance our understanding of the assembly mechanism of secretin complexes within the secretin superfamily. Enteropathogenic Escherichia coli produces bundle-forming pili that facilitate bacterial adhesion and colonization. Here, the authors report a high-resolution structure of the BfpB-BfpG secretin channel complex, which enables pilus translocation across the outer membrane, revealing an unusual 17:17 stoichiometry and providing insights into its assembly mechanism.

Source: Nature Communications

DOI: 10.1038/s41467-025-65063-w