Thrombin activation of the factor XI dimer is a multistaged process for each subunit

Area of Science:

• Biochemistry
• Molecular Biology
• Hemostasis

Background:

• Factor XI (FXI) activation by proteases like thrombin is transient and difficult to study.
• Understanding FXI activation dynamics is crucial for hemostasis research.

Purpose of the Study:

• Identify the thrombin-FXI binding interface.
• Elucidate the dynamics of thrombin-mediated FXI activation.

Main Methods:

• Crosslinking mass spectrometry to map the binding site.
• Molecular dynamics simulations to analyze conformational changes.
• Utilized nanobody 1C10 to validate the activation pathway.

Main Results:

• Identified thrombin's binding interface on FXI light chain at Pro520.
• FXI undergoes conformational changes involving the apple 1 domain for activation.
• Thrombin binds but does not activate prekallikrein, despite conserved Pro520.

Conclusions:

• FXI activation is a multistep process initiated by thrombin binding to Pro520.
• Thrombin migration to the apple 1 domain facilitates cleavage site access.
• Detailed interaction analysis offers potential for therapeutic interventions in bleeding/thrombosis.