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Related Experiment Video

Updated: Jun 28, 2026

High Resolution Electron Microscopy of the Helicobacter pylori Cag Type IV Secretion System Pili Produced in Varying Conditions of Iron Availability

High Resolution Electron Microscopy of the Helicobacter pylori Cag Type IV Secretion System Pili Produced in Varying Conditions of Iron Availability

Published on: November 21, 2014

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.

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Covalent Immobilization of Proteins for the Single Molecule Force Spectroscopy

Covalent Immobilization of Proteins for the Single Molecule Force Spectroscopy

Published on: August 20, 2018

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Last Updated: Jun 28, 2026

High Resolution Electron Microscopy of the Helicobacter pylori Cag Type IV Secretion System Pili Produced in Varying Conditions of Iron Availability

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Published on: November 21, 2014

Covalent Immobilization of Proteins for the Single Molecule Force Spectroscopy

Covalent Immobilization of Proteins for the Single Molecule Force Spectroscopy

Published on: August 20, 2018

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.