Prothrombin residues 473-487 contribute to factor Va binding in the prothrombinase complex

Area of Science:

• Biochemistry
• Molecular Biology
• Hematology

Background:

• The prothrombinase complex, comprising factor Xa (fXa), factor Va (fVa), prothrombin (fII), and phospholipids, is crucial for blood coagulation.
• Identifying specific protein-protein interactions within this complex is essential for understanding hemostasis and developing targeted therapies.

Purpose of the Study:

• To identify prothrombin (fII) sequences involved in the assembly of the prothrombinase complex.
• To investigate the interaction between prothrombin and factor Va (fVa) within the prothrombinase complex.

Main Methods:

• Synthesis and screening of synthetic peptides based on fII sequences for inhibition of fXa-induced plasma clotting.
• Assessing prothrombinase activity and amidolytic activities of fXa and thrombin.
• Utilizing fluorescein-labeled fVa (Fl-fVa) and anisotropy measurements to study peptide-fVa interactions.

Main Results:

• The fII peptide PT473-487 potently inhibited plasma clotting and prothrombinase activity in a factor Va (fVa)-dependent manner.
• PT473-487 did not inhibit the amidolytic activity of fXa or thrombin, indicating specificity.
• Fluorescence anisotropy data demonstrated a direct binding interaction between PT473-487 and phospholipid-bound Fl-fVa.

Conclusions:

• Prothrombin (fII) residues 473-487 mediate the interaction with factor Va (fVa).
• These residues provide critical fVa-binding sites essential for prothrombinase complex assembly.
• The findings elucidate specific molecular interactions governing blood coagulation.