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Energetics of thrombin-thrombomodulin interaction
A Vindigni1, C E White, E A Komives
1Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Biochemistry
|June 3, 1997
Summary
Thrombin-thrombomodulin interaction is driven by electrostatic steering and involves enzyme conformational changes, significantly enhanced by chondroitin sulfate. This binding modulates thrombin
Area of Science:
- Biochemistry
- Molecular Biology
- Protein Interactions
Background:
- Thrombin is a key enzyme in hemostasis.
- Thrombomodulin acts as a crucial cofactor for thrombin.
- Understanding their interaction mechanism is vital for physiological insights.
Purpose of the Study:
- To elucidate the energetic signatures and recognition mechanism of thrombin-thrombomodulin interaction.
- To investigate the role of salt, chondroitin sulfate, and specific thrombomodulin domains.
- To determine the impact of this interaction on thrombin's enzymatic activity.
Main Methods:
- Temperature and salt dependence studies.
- Analysis of thrombin interaction with thrombomodulin and its fragments.
- Assays measuring enzyme kinetics and substrate hydrolysis.
Main Results:
- Thrombin-thrombomodulin binding is highly sensitive to salt concentration, with Na+ promoting and Cl- opposing the interaction.
- Chondroitin sulfate significantly enhances binding affinity through electrostatic interactions with the heparin-binding site.
- Thrombomodulin binding induces conformational changes in thrombin's slow form, increasing its specificity towards certain substrates.
Conclusions:
- Thrombin-thrombomodulin recognition is electrostatically steered, with chondroitin sulfate playing a major role in affinity enhancement.
- The interaction involves conformational transitions in thrombin, particularly in its slow form.
- Thrombomodulin enhances protein C cleavage by altering the substrate (protein C) rather than modifying thrombin's enzymatic efficiency.