Molecular Interactions of Human Plasminogen with Fibronectin-binding Protein B (FnBPB), a...

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Staphylococcus aureus is a versatile bacterium causing various infections.
• Pathogens like S. aureus hijack host proteins, such as plasminogen, for invasion.
• Sortase-anchored cell wall proteins mediate pathogen-host interactions.

Purpose of the Study:

• To investigate the role of S. aureus cell wall proteins in plasminogen binding.
• To characterize the interaction between fibronectin-binding protein B (FnBPB) and plasminogen.
• To determine the mechanism and binding site of plasminogen capture by FnBPB.

Main Methods:

• Surface plasmon resonance (SPR) to quantify FnBPB-plasminogen binding affinity.
• Expression of recombinant FnBPB in Lactococcus lactis and S. aureus.
• Site-directed mutagenesis and biochemical assays to identify binding domains.

Main Results:

• Sortase-anchored cell wall proteins are primarily responsible for plasminogen binding.
• FnBPB binds plasminogen with a dissociation constant (KD) of 0.532 μm.
• FnBPB binds plasminogen independently of fibrinogen binding, with the N3 subdomain containing the binding site, including lysine residues.

Conclusions:

• FnBPB effectively captures and presents plasminogen for activation by host or bacterial factors.
• The distinct binding mechanism allows simultaneous interaction with plasminogen and fibrinogen.
• Understanding this interaction is crucial for developing strategies against S. aureus infections.