Staphylococcus aureus protein A binding to von Willebrand factor A1 domain is mediated by conserved IgG binding regions

Abstract

Protein A (Spa) is a surface‐associated protein of Staphylococcus aureus best known for its ability to bind to the Fc region of IgG. Spa also binds strongly to the Fab region of the immunoglobulins bearing VH3 heavy chains and to von Willebrand factor (vWF). Previous studies have suggested that the protein A–vWF interaction is important in S. aureus adherence to platelets under conditions of shear stress. We demonstrate that Spa expression is sufficient for adherence of bacteria to immobilized vWF under low fluid shear. The full length recombinant Ig‐binding region of protein A, Spa‐EDABC, fused to glutathione‐S‐transferase (GST), bound recombinant vWF in a dose‐dependent and saturable fashion with half maximal binding of about 30 nm in immunosorbent assays. Full length‐Spa did not bind recombinant vWF A3 domain but displayed binding to recombinant vWF domains A1 and D′‐D3 (half maximal binding at 100 nm and 250 nm, respectively). Each recombinant protein A Ig‐binding domain bound to the A1 domain in a similar manner to the full length‐Spa molecule (half maximal binding 100 nm). Amino acid substitutions were introduced in the GST‐SpaD protein at sites known to be involved in IgG Fc or in VH3 Fab binding. Mutants altered in residues that recognized IgG Fc but not those that recognized VH3 Fab had reduced binding to vWF A1 and D′‐D3. This indicated that both vWF regions recognized a region on helices I and II that overlapped the IgG Fc binding site.

Ultralarge von Willebrand Factor Fibers Mediate Luminal Staphylococcus aureus Adhesion to an Intact Endothelial Cell Layer Under Shear Stress

“…However, at highshear-flow conditions, we measured an SpA-independent S aureus adhesion (Figure 4). Notably, these findings of a shear flow dependency are supported by results obtained by O'Seaghdha and coworkers 35 showing that Lactococcus lactis derivatives expressing the SpA bind to recombinant human VWF under low shear rates but not under high shear rates. To reveal the potential bacterial binding partner for VWF under high-shear-flow conditions, we first determined the interaction between VWF and S aureus srtA, which lacks all cell wall-anchored surface proteins.…”

Recent human-to-poultry host jump, adaptation, and pandemic spread of Staphylococcus aureus

“…An identical spA nonsense mutation was found in all poultry ST5 strains examined, indicating that it happened early in the evolution of the poultry ST5 clade. SpA has multiple roles in the pathogenesis of human infections, including adherence to lung epithelium via the TNFR1 receptor (19), binding to human platelets through its interaction with von Willebrand factor (20,21), and inhibition of opsonophagocytosis resulting from non-specific binding of the Fc region of IgG (22,23). Of note, the avian equivalent of human IgG is IgY, which has a structurally distinct Fc region that does not bind to SpA (24,25), suggesting that SpA would not contribute to the inhibition of opsonophagocytosis in birds.…”

Suppression of conformational heterogeneity at a protein–protein interface

“…SpA binding mimics TNF-α activation of airway cells, leading to inflammation (5). SpA also binds the A1 domain of the hemostasis protein von Willebrand factor (vWf) with 15-nM affinity (6) using residues on helix 1 (Q10, F13, Y14, and L17) and helix 2 (N28, I31, and K35), which allows S. aureus to adhere to surfaces (7).…”