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Published on: December 17, 2013
Structural basis of chaperone self-capping in P pilus biogenesis
D L Hung1, J S Pinkner, S D Knight
1Department of Molecular Microbiology, Box 8230, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
Summary
PapD chaperone prevents premature P pilus assembly in E. coli by binding subunits. It also self-caps its binding surface, revealed by crystal structures, ensuring proper assembly regulation.
Area of Science:
- Microbiology
- Structural Biology
- Molecular Mechanisms
Background:
- PapD is an immunoglobulin-like chaperone essential for P pilus assembly in uropathogenic Escherichia coli.
- It prevents premature subunit association in the periplasm by capping interactive surfaces.
Purpose of the Study:
- To elucidate the structural basis of PapD's self-capping mechanism.
- To understand how PapD regulates its own activity and subunit binding.
Main Methods:
- X-ray crystallography to determine the structure of dimeric PapD.
- Site-directed mutagenesis to analyze the role of specific surfaces in dimerization and subunit binding.
Main Results:
- Crystal structures revealed PapD dimers with rearranged C2-D2 and F1-G1 loops, indicating a self-capping mechanism.
- This self-capping involves the same surface PapD uses to bind pilus subunits.
- Mutagenesis confirmed that the subunit-binding surface is required for chaperone dimerization.
Conclusions:
- PapD self-interaction caps its own subunit-binding site, providing a regulatory mechanism for P pilus assembly.
- This structural insight explains how PapD ensures precise control over pilus biogenesis in E. coli.
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