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Core architecture of a bacterial type II secretion system
Anastasia A Chernyatina1, Harry H Low2
1Department of Life Sciences, Imperial College, London, SW7 2AZ, UK.
Nature Communications
|November 30, 2019
Summary
Bacterial type II secretion systems (T2SSs) are crucial for pathogen virulence. This study reveals the dynamic, modular architecture of a T2SS from Klebsiella pneumoniae, detailing its protein complex structure.
Area of Science:
- Microbiology
- Structural Biology
- Biochemistry
Background:
- Bacterial type II secretion systems (T2SSs) are essential protein machineries for translocating diverse substrates across the bacterial outer membrane.
- Understanding the structural basis of T2SS assembly and function is critical for developing novel antimicrobial strategies.
Purpose of the Study:
- To elucidate the high-resolution architecture of an assembled T2SS from the pathogen Klebsiella pneumoniae.
- To characterize the protein-protein interactions and stoichiometry within the T2SS complex.
Main Methods:
- Negative stain electron microscopy
- Cryo-electron microscopy
- Protein complex structural analysis
Main Results:
- A ~2.4 MDa T2SS complex composed of 7 proteins was structurally characterized.
- The outer membrane complex comprises the secretin PulD and pilotin PulS.
- The inner membrane platform consists of PulC, PulE, PulL, PulM, and PulN in a 2:1:1:1:1 ratio, forming a dynamic hexameric hub.
- Symmetry mismatch is resolved by PulC linkers and independent binding of PulC HR domains to the secretin base.
Conclusions:
- The T2SS exhibits a highly dynamic and modular architecture.
- Structural insights provide a framework for understanding pseudo-pilus assembly and substrate translocation.
- This work lays the foundation for targeting T2SS in bacterial pathogens.
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