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Molecular mapping of thrombin-receptor interactions.
Y M Ayala1, A M Cantwell, T Rose
1Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Proteins
|September 20, 2001
Summary
Thrombin
Area of Science:
- Biochemistry
- Molecular Biology
- Proteolysis
Background:
- Thrombin plays dual roles in blood coagulation and cell signaling.
- It signals by interacting with protease-activated receptors (PARs): PAR1, PAR3, and PAR4.
Purpose of the Study:
- To map thrombin's binding epitopes for PAR1, PAR3, and PAR4.
- To elucidate the molecular basis for differential receptor specificity.
Main Methods:
- Enzymatic assays
- Alanine scanning mutagenesis
- 3D structural modeling
Main Results:
- Thrombin epitopes for PARs largely overlap with fibrinogen/fibrin binding sites.
- Key residues in the active site and exosite I dictate PAR-specific recognition.
- Mutations reveal distinct hierarchies of effects on PAR4, PAR3, and PAR1 binding.
- Specific mutations (W215A, R67A) selectively alter receptor cleavage and specificity.
Conclusions:
- Structural mapping and mutagenesis identify critical thrombin residues for PAR interactions.
- These findings explain thrombin's differential specificity for PAR1, PAR3, and PAR4.
- 3D models provide a structural basis for observed mutagenesis data.