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Rapid kinetics of Na+ binding to thrombin
Alaji Bah1, Laura C Garvey, Jingping Ge
1Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
The Journal of Biological Chemistry
|November 1, 2006
Summary
Sodium (Na+) binding to thrombin occurs in a two-step kinetic mechanism. This binding induces long-range structural changes in the enzyme, impacting blood clotting factors.
Area of Science:
- Biochemistry
- Enzymology
- Structural Biology
Background:
- Thrombin plays a crucial role in blood coagulation.
- Monovalent cations, like sodium (Na+), can allosterically modulate enzyme activity.
- Understanding Na+ binding kinetics is key to comprehending thrombin function.
Purpose of the Study:
- To elucidate the kinetic mechanism of Na+ binding to thrombin.
- To identify the specific tryptophan (Trp) residues involved in Na+ binding.
- To investigate the structural consequences of Na+ binding on thrombin.
Main Methods:
- Stopped-flow measurements of intrinsic fluorescence.
- Site-directed mutagenesis of thrombin's tryptophan residues.
- Temperature-dependent kinetic studies.
Main Results:
- Na+ binding to thrombin follows a two-step mechanism: a rapid phase and a slow phase.
- Specific Trp residues (Trp-141, Trp-215) are primarily involved in fluorescence changes.
- Na+ binding induces long-range structural effects across the entire thrombin enzyme.
Conclusions:
- The study reveals a detailed kinetic mechanism for Na+ binding to thrombin.
- Na+ binding influences thrombin's structure globally, not just locally.
- Findings are relevant for understanding cation modulation in other clotting factors and enzymes.
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