Proposed structural models of human factor Va and prothrombinase

Area of Science:

• Biochemistry
• Structural Biology
• Computational Biology

Background:

• The prothrombinase complex, comprising factor Xa, factor Va, calcium ions, and a phospholipid membrane, is essential for blood coagulation.
• Understanding the structure of this complex is vital for comprehending hemostasis and developing related therapeutics.

Purpose of the Study:

• To generate solvent-equilibrated structural models of human factor Va (FVa) and the complete prothrombinase complex.
• To investigate the conformational dynamics of FVa and its interactions within the prothrombinase complex.

Main Methods:

• Homology modeling was used to build initial structural templates for FVa.
• Protein-protein docking and molecular dynamics simulations were employed to refine models and assess complex stability.
• Experimental data served as filters during the docking process to ensure biologically relevant interactions.

Main Results:

• Molecular dynamics simulations indicated a potential shift towards planarity in the five domains of the FVa model.
• Docking of a factor Xa (FXa) model to the equilibrated FVa model revealed alterations in protein-protein contacts upon simulation of the complex.
• The simulation did not significantly change the buried surface area between FXa and FVa compared to the initial docking model.

Conclusions:

• The study provides refined structural models of human FVa and the prothrombinase complex.
• The findings suggest conformational flexibility in FVa and highlight dynamic changes within the complex during simulation.
• Potential binding sites for prothrombin on the prothrombinase complex were identified, offering insights for future functional studies.