Dimerization Energetics of Curli Fiber Subunits CsgA and CsgB
Journal Article - Open Access
Northwestern University Evanston United States
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Curli fibers are functional amyloids that exhibit strong adhesion and robust self-assembly as biofilm structural components however, the binding energetics and mechanical properties of wild-type curli are not well understood. To address this, we present dimer structures made up of the major and minor curli subunits CsgA and CsgB, perform free energy calculations to obtain absolute binding energies, and estimate the Youngs modulus and persistence length of curli fibers. Equilibrium molecular dynamics simulations are used to evaluate nonbonded interactions. Binding energies are most favorable for CsgBCsgA, while CsgACsgA dimers have a higher binding energy than CsgBCsgB despite possessing less favorable nonbonded interaction energies. Decomposing each potential of mean force of separation indicated that solvent effects positively impact CsgACsgA binding but not CsgBCsgB and CsgBCsgA. Charged residues and conserved polar residues were also notable contributors to attractive nonbonded interactions, underlining their importance in dimer assembly. Our findings elucidate sequence effects on binding energy contributions and establish theoretical limits for the elasticity, persistence length, and strength of curli fibers.
- Atomic and Molecular Physics and Spectroscopy