Study on complex formation between recombinant human thrombomodulin fragment and thrombin using surface plasmon...

Area of Science:

• Biochemistry
• Molecular Biology
• Hematology

Background:

• Human thrombomodulin (hTM) is an endothelial cell protein with significant anticoagulant properties.
• hTM converts thrombin from a procoagulant to an anticoagulant enzyme, regulating blood clotting.
• Understanding the binding kinetics of hTM with thrombin is crucial for its therapeutic applications.

Purpose of the Study:

• To determine the affinity constants of recombinant human soluble TM (rhs-TM) and an active site hTM fragment (f-hTM) for thrombin.
• To elucidate the interaction dynamics between hTM variants and thrombin.
• To compare the binding characteristics of rhs-TM and f-hTM.

Main Methods:

• Surface plasmon resonance (SPR) was employed to measure the binding kinetics.
• SPR analysis allowed for the characterization of association and dissociation rates.
• Kinetic data were analyzed using appropriate binding models.

Main Results:

• The interaction of f-hTM with thrombin followed a simple binding model.
• The interaction of rhs-TM with thrombin involved at least two distinct phases.
• The dissociation constant (K(D)) for f-hTM-thrombin complex was 205 nM, significantly higher than rhs-TM (6.7 and 75 nM).
• f-hTM exhibited lower affinity due to a rapid dissociation rate, not a slow association rate.

Conclusions:

• f-hTM interacts rapidly with thrombin, but with lower overall affinity compared to rhs-TM.
• The binding of rhs-TM to thrombin is more complex, involving multiple interaction phases.
• These findings provide insights into the molecular interactions governing hTM's anticoagulant function.