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<p>The bundle-forming pilus (BFP) system in enteropathogenic <i>Escherichia coli</i> (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.</p>

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

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年10月16日

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  • Chenchen Pei,
  • Hui Sun,
  • Yinliang Qi,
  • Xiaomei Li,
  • Zhixiong Fang,
  • Manjuan Tang,
  • Rujing Zhang,
  • Zhaofeng Yan,
  • Meng Yin

摘要

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.