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Modulation of thrombin-hirudin interaction by specific ion effects
R De Cristofaro1, J W Fenton, E Di Cera
1Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, MO 63110.
Journal of Molecular Biology
|July 5, 1992
Summary
Specific ions influence thrombin-hirudin interactions, affecting inhibition. Ion release mechanisms, similar to those seen with fibrinogen, modulate this interaction, impacting the association rate constant.
Area of Science:
- Biochemistry
- Enzymology
- Protein-protein interactions
Background:
- Thrombin is a key enzyme in blood coagulation.
- Hirudin is a potent thrombin inhibitor.
- The interaction between thrombin and hirudin is crucial for anticoagulation.
Purpose of the Study:
- To investigate the role of salt concentration and specific ions on thrombin-hirudin interaction kinetics.
- To elucidate the mechanism of ion release in thrombin-hirudin binding.
- To compare ion effects in thrombin-hirudin interaction with thrombin-fibrinogen interaction.
Main Methods:
- Kinetic studies of thrombin amidase activity inhibition by recombinant hirudin.
- Experiments conducted across a range of salt concentrations (0.05 to 1 M) using various salts (NaCl, KCl, NaBr, KBr).
- Analysis of the relationship between inhibition constant (KI) and mean ion activity.
Main Results:
- The inhibition constant (KI) for thrombin-hirudin interaction varies with different salts at the same ionic strength.
- Specific ion effects, particularly ion release, modulate thrombin-hirudin binding.
- The order of ion release follows NaBr > NaCl > KCl > KBr, consistent with thrombin-fibrinogen interactions.
Conclusions:
- Specific ion effects play a significant role in modulating thrombin-hirudin interactions.
- Ion release is a key mechanism in the binding of hirudin to thrombin.
- The findings suggest a conserved ion linkage hierarchy across different thrombin interactions.