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Entropic bonding of the type 1 pilus from experiment and simulation
Fabiano Corsetti1,2,3,4, Alvaro Alonso-Caballero4,5, Simon Poly4,6
1Department of Materials, Imperial College London, London SW7 2AZ, UK.
Royal Society Open Science
|May 21, 2020
Summary
The stability of bacterial type 1 pili, crucial for uropathogenic Escherichia coli, arises from the entropic nature of subunit unravelling and detachment. This study quantifies pilus strength, revealing its entropic origins.
Area of Science:
- Bacterial adhesion mechanisms
- Biophysics of protein interactions
- Structural biology of pili
Background:
- Type 1 pili are essential for uropathogenic Escherichia coli adhesion.
- Pilus strength and stability are critical for bacterial anchoring.
- Previous studies explored FimG subunit unravelling using AFM and simulations.
Purpose of the Study:
- To quantitatively compare experimental and simulation data for pilus subunit unfolding.
- To estimate the free energy of FimG detachment from the FimF subunit.
- To elucidate the entropic contribution to pilus chain stability.
Main Methods:
- Atomic force microscopy (AFM) experiments.
- Steered molecular dynamics (MD) simulations.
- Quantitative comparison of experimental and simulation work values.
- Free energy calculations for subunit detachment.
Main Results:
- Good agreement was found between experimental and simulation work values for pilus subunit unfolding.
- The free energy difference for FimG detachment from FimF was estimated using simulation data.
- The high stability of the type 1 pilus chain is primarily due to entropic factors.
Conclusions:
- The study validates simulation accuracy by comparing it with AFM experiments.
- The unravelling and detachment of pilus subunits are energetically favorable due to entropy.
- Understanding these entropic forces provides insights into bacterial adhesion and pilus function.