| Title | Role of P2 Glycine in Determining the Specificity of Antithrombin Reaction with Coagulation Proteases. | | Author(s) | Yang L, Qureshi SH, Manithody C, Rezaie AR | | Institution | From the Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, Saint Louis, Missouri 63104. | | Source | Biochem Biophys Res Commun 2009 Aug 25. | | Abstract | Structural data suggests that bulky hydrophobic residues at the S2-S4 sub-sites of factor Xa (fXa) restrict the preference of this pocket for small and non-polar residues like Gly at the P2 position of substrates and inhibitors. However, kinetic studies monitoring the cleavage specificity of 10-residue peptides by fXa have identified Phe as the most preferred P2 residue and Gln-Phe-Arg-Ser-Leu-Ser as the most preferred P3-P3' residues for recognition by fXa. To determine whether this mechanism of specificity is also true for fXa reaction with antithrombin (AT), we prepared two AT mutants having either a Phe at the P2 or Gln-Phe-Arg-Ser-Leu-Ser at the P3-P3' positions of the reactive center loop. Inhibition kinetic studies indicated that the reactivity of P2-Phe with fXa was significantly ( approximately 5-fold) impaired, however, the P3-P3' mutant exhibited 1.5-fold improved reactivity with the protease, suggesting cooperative effects between P3-P3' residues influence the P2 specificity of AT. Substitution of Tyr-99 of fXa with a Gly dramatically impaired the reactivity of fXa with wild-type AT, but improved its reactivity with the serpin mutants in the absence, but not in the presence of pentasaccharide. AT with a P2-Phe inhibited thrombin with >150-fold impaired reactivity, however, the defect was restored by either pentasaccharide or by replacing Leu-99 of thrombin with a Gly. The P3-P3' mutant rapidly inhibited factors VIIa and XIa independent of pentasaccharide. These results indicate that P2-Gly plays a key role in determining the S2 sub-site specificity and target protease selectivity of AT in circulation. | | Language | ENG | | Pub Type(s) | JOURNAL ARTICLE
| | PubMed ID | 19715676 |
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