The structure of F-pili
Ying A Wang1, Xiong Yu, Philip M Silverman
1Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908-0733, USA.
Journal of Molecular Biology
|November 11, 2008
Summary
Bacterial conjugation relies on F-pili, which may act as DNA channels. This study reveals unique F-pilus structures with two coexisting symmetries, differing from known pili and phages, and large enough for DNA passage.
Area of Science:
- Microbiology
- Structural Biology
- Molecular Biology
Background:
- Bacterial DNA exchange occurs via conjugative pili.
- F-pili are crucial for bacterial conjugation, but their structure and function remain poorly understood.
- Recent findings suggest F-pili may serve as DNA channels during conjugation.
Purpose of the Study:
- To elucidate the structure and subunit packing of F-pili.
- To resolve ambiguities in the geometric arrangement of F-pilin subunits.
- To understand the structural basis for F-pilus function in DNA transfer.
Main Methods:
- Electron cryo-microscopy
- Single-particle analysis
- Structural determination of F-pilin subunit packing
Main Results:
- F-pili exhibit unique symmetries distinct from other bacterial pili and filamentous bacteriophages.
- Two distinct subunit packing schemes were identified: stacked rings and one-start helical symmetry.
- Both schemes feature a central lumen (approx. 30 A diameter) capable of ssDNA passage.
- Remarkably, these two symmetries coexist within the same F-pilus filaments.
Conclusions:
- F-pili possess a novel structure with coexisting symmetries, challenging previous models.
- The determined structures support the role of F-pili as channels for single-stranded DNA during conjugation.
- This structural plasticity may be a conserved feature in certain archaeal filaments.
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