Fibrinogen binding is affected by amino acid substitutions in C-terminal repeat region of fibronectin binding protein A.

Published online

Journal Article

Fibronectin-binding protein A (FnBPA), a protein displayed on the outer surface of Staphylococcus aureus, has a structured A-domain that binds fibrinogen (Fg) and a disordered repeat-region that binds fibronectin (Fn). Amino acid substitutions in Fn-binding repeats (FnBRs) have previously been linked to cardiovascular infection in humans. Here we used microtiter and atomic force microscopy (AFM) to investigate adhesion by variants of full-length FnBPA covalently anchored in the outer cell wall of Lactococcus lactis, a Gram-positive surrogate that otherwise lacks adhesins to mammalian ligands. Fn adhesion increased in five of seven FnBPA variants under static conditions. The bond targeting Fn increased its strength with load under mechanical dissociation. Substitutions extended bond lifetime (1/koff) up to 2.1 times for FnBPA-Fn. Weaker adhesion was observed for Fg in all FnBPA variants tested with microtiter. However, mechanical dissociation with AFM showed significantly increased tensile strength for Fg interacting with the E652D/H782Q variant. This is consistent with a force-induced mechanism and suggests that the dock, lock, and latch (DLL) mechanism is favored for Fg-binding under mechanical stress. Collectively, these experiments reveal that FnBPA exhibits bimodal, ligand-dependent adhesive behavior. Amino acid substitutions in the repeat-region of FnBPA impact binding to both ligands. This was unexpected for Fg since all variants have the same A-domain sequence, and the Fg-binding site is distant from the repeat region. This indicates that FnBRs may fold back on the A-domain in a way that impacts the DLL binding mechanism for Fg.

Full Text

Duke Authors

Cited Authors

  • Casillas-Ituarte, NN; DiBartola, AC; Broughton, MJ; Pérez-Guzmán, L; Wheeler, RM; Ibaraki, M; Lower, BA; Dunn, JA; Lower, BH; Fowler, VG; Hӧӧk, M; McIntyre, LM; Lower, SK; Sharma-Kuinkel, BK

Published Date

  • August 12, 2019

Published In

Volume / Issue

  • 9 / 1

Start / End Page

  • 11619 -

PubMed ID

  • 31406152

Pubmed Central ID

  • 31406152

Electronic International Standard Serial Number (EISSN)

  • 2045-2322

Digital Object Identifier (DOI)

  • 10.1038/s41598-019-48031-5

Language

  • eng

Conference Location

  • England