title: Adhesion mechanisms of curli subunit CsgA to abiotic surfaces.
abstract: Curli fibers are functional amyloids that play a key role in biofilm structure and adhesion to various surfaces. Strong bioinspired adhesives comprising curli fibers have recently been created; however, the mechanisms curli uses to attach onto abiotic surfaces are still uncharacterized. Toward a materials-by-design approach for curli-based adhesives and multifunctional materials, we examine curli subunit adsorption onto graphene and silica surfaces through atomistic simulation. We find that both structural features and sequence influence adhesive strength, enabling the CsgA subunit to adhere strongly to both polar and nonpolar surfaces. Specifically, flexible regions facilitate adhesion to both surfaces, charged and polar residues (Arg, Lys, and Gln) enable strong interactions with silica, and six-carbon aromatic rings (Tyr and Phe) adsorb strongly to graphene. We find that adsorption not only lowers molecular mobility but also leads to loss of secondary structure, factors that must be well balanced for effective surface attachment. Both events appear to propagate through the CsgA structure as correlated motion between clusters of residues, often H-bonded between rows on adjacent β strands. To quantify this, we present a correlation analysis approach to detecting collective motion between residue groups. We find that certain clusters of residues have a higher impact on the stability of the rest of the protein structure, often polar and bulky groups within the helix core. These findings lend insight into bacterial adhesion mechanisms and reveal strategies for theory-driven design of engineered curli fibers that harness point mutations and conjugates for stronger adhesion.
authors.affiliation: Departments of Civil and Environmental Engineering and Mechanical Engineering, Northwestern University, Evanston, IL 60208, USA.
authors.forename: Elizabeth P
authors.identifier: 0000-0003-3149-7585
authors.initials: EP
authors.lastname: DeBenedictis
authors.affiliation: Northwestern University Medical Scientist Training Program, Northwestern University, Evanston, IL 60208, USA.
authors.forename: Jenny
authors.identifier: 0000-0002-2867-8687
authors.initials: J
authors.lastname: Liu
authors.affiliation: Departments of Civil and Environmental Engineering and Mechanical Engineering, Northwestern University, Evanston, IL 60208, USA.
authors.forename: Sinan
authors.initials: S
authors.lastname: Keten
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics; D006860:Hydrogen Bonding; D056004:Molecular Dynamics Simulation; D000072417:Protein Domains
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C489688:csgA protein, E coli; C077481:Crl protein, Bacteria
keywords: CsgA; Curli; adhesives; adsorption; biofilm; graphene; materials design; molecular dynamics; protein binding