Structural insights into the secretin complex of a type IVb pilus system
Chenchen Pei1, Hui Sun1, Yinliang Qi2
1Affiliated Hospital of Hunan University/Xiangtan Central Hospital, School of Biomedical Sciences, Hunan University, Changsha, China.
Nature Communications
|October 16, 2025
Summary
Enteropathogenic E. coli uses the bundle-forming pilus (BFP) system for adhesion. We determined the BfpB-BfpG complex structure, revealing its role in pilus translocation and BFP biogenesis.
Area of Science:
- Microbiology
- Structural Biology
- Biochemistry
Background:
- The bundle-forming pilus (BFP) system in enteropathogenic Escherichia coli (EPEC) is crucial for bacterial adhesion and virulence.
- BFP production relies on a secretin channel complex formed by lipoproteins BfpB and BfpG for pilus translocation.
Purpose of the Study:
- To elucidate the high-resolution structure of the BfpB-BfpG complex.
- To understand the molecular mechanisms underlying BFP biogenesis and pilus translocation.
Main Methods:
- High-resolution cryo-electron microscopy (cryo-EM).
Main Results:
- Determined the cryo-EM structure of the BfpB-BfpG complex with a 17:17 stoichiometry.
- Identified stable zigzag-like interactions between BfpG and BfpB near the N3 ring.
- Revealed that BfpB contains three β-barrels, including a critical N3 barrel for BFP biogenesis, and its N-terminal LG domain mediates outer membrane localization and BfpG binding.
Conclusions:
- The BfpB-BfpG complex structure provides insights into the assembly of secretin complexes.
- Understanding these interactions is vital for BFP biogenesis and EPEC virulence.
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