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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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Purification and three-dimensional electron microscopy structure of the Neisseria meningitidis type IV pilus

Richard F Collins1, Muhammad Saleem, Jeremy P Derrick

  • 1Faculties of Life Sciences and Engineering/Physical Sciences, Manchester Interdisciplinary Biocentre, University of Manchester, 131 Princess Street, Manchester, United Kingdom.

Journal of Bacteriology
|July 10, 2007
PubMed

Insights

This study reveals the first 3-D structure of PilG, a key protein in type IV pilus assembly. The structure suggests how PilG links inner and outer cellular components in gram-negative bacteria.

Area of Science:

  • Microbiology
  • Structural Biology
  • Biochemistry

Background:

  • Type IV pili are crucial for Neisseria meningitidis pathogenesis.
  • PilG is an inner membrane protein essential for type IV pilus biogenesis.
  • PilG belongs to the GspF family of secretory proteins.

Purpose of the Study:

  • To determine the three-dimensional structure of the PilG multimer.
  • To elucidate the structural basis for PilG's role in type IV pilus biogenesis.

Main Methods:

  • Overexpression and purification of PilG from E. coli membranes.
  • Detergent extraction and metal ion affinity chromatography for purification.
  • 3-D electron microscopy with single-particle averaging and negative staining.

Main Results:

  • PilG forms stable dimers and tetramers in solution.
  • A 3-D reconstruction revealed an asymmetric bilobed structure of the PilG tetramer.
  • The N-terminus was identified, and the structure suggests transmembrane and periplasmic domains.

Conclusions:

  • This is the first 3-D structure reported for a GspF family member.
  • The structure provides insights into PilG's function in linking cellular components for pilus assembly.
  • The findings support a model for PilG's role in type II secretion and type IV pilus systems.

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