Kinetic pathway for the slow to fast transition of thrombin. Evidence of linked ligand binding at structurally distinct domains.
Research article published in The Journal of biological chemistry (1997)
Abstract
The kinetic pathway for the Na+-induced slow --> fast transition of thrombin was characterized. The slow form was shown to consist of two conformers in a 3:1 ratio (ES2:ES1) at 5 degrees C, pH 7.4, Gamma/2 0.3. ES2 binds Na+ 3 orders of magnitude faster than does ES1. The small molecule active site-directed inhibitor L-371,912, and the exosite I binding ligand hirugen, like Na+, bind selectively to ES2 and induce the slow --> fast conversion of thrombin. The slow --> fast transition is limited by the rate of conversion of ES1 to ES2 (k approximately 28 s-1 at 5 degrees C). Replacement of Arg-221a or Lys-224 at the Na+ binding site with Ala appears to selectively alter the slow form and reduce the apparent affinity of the mutants for Na+ and L-371,912. This replacement, however, has little effect on the affinity for the inhibitor in the presence of saturating concentrations of Na+. The kinetically linked ligand binding at the Na+ binding site, exosite I, and the active site of thrombin characterized in the present study indicates the basis for the plasticity of this important enzyme, and suggests the possibility that the substrate specificity and, therefore, the procoagulant and anticoagulant activities of thrombin may be subject to allosteric regulation by as yet unidentified physiologically important effectors.
Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.
Zusammenfassung
The kinetic pathway for the Na+-induced slow --> fast transition of thrombin was characterized. The slow form was shown to consist of two conformers in a 3:1 ratio (ES2:ES1) at 5 degrees C, pH 7.4, Gamma/2 0.3.
Warum dies für die Hirudotherapie relevant ist
The abstract characterizes the kinetic pathway of thrombin's Na+-induced slow-to-fast transition, identifying two slow-form conformers and showing that the active-site-directed inhibitor L-371,912 and the exosite I binding ligand hirugen each bind selectively to one conformer and induce the slow-to-fast conversion. Mutations at Arg-221a or Lys-224 alter the slow form and reduce apparent affinity for Na+ and L-371,912. The only possible ASH-domain hook in the abstract is the named ligand 'hirugen,' but the abstract does not state that it is leech-derived, hirudin-derived, or related to hirudotherapy. Thus, no direct leech or hirudotherapy relevance is established by the abstract itself; relevance remains limited to thrombin allostery and ligand-binding kinetics.
Zitation
Kinetic pathway for the slow to fast transition of thrombin. Evidence of linked ligand binding at structurally distinct domains.
Lai et al. · The Journal of biological chemistry, 1997
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