Affiliation:
1. Sol Sherry Thrombosis Research Center, Department of Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA.
Abstract
Binding sites for high molecular weight kininogen (HK) and for factor XIIa are present in the Apple 1 (A1) and the A4 domains of factor XI, respectively. To define the roles of these two sites in surface-mediated factor-XI activation we prepared conformationally constrained synthetic peptides and recombinant A1 domain (rA1) and determined their effects on the activation of factor XI by factor XIIa in the presence of HK and either kaolin or dextran sulfate. Surface-mediated factor-XI activation by factor XIIa was inhibited by a conformationally constrained A4 peptide (Ala317-Gly350), by an A1 peptide (Phe56-Ser86), and by rA1 (Glu1-Ser90). When used in combination at equimolar concentrations, rA1 and A4 peptide were 10-fold more effective than either one alone in inhibiting surface-mediated activation of factor XI by factor XIIa. The A4 peptide was a competitive inhibitor of factor XIIa amidolytic activity and a noncompetitive inhibitor of factor-XI activation by factor XIIa, whereas rA1 and the A1 peptide did not inhibit factor XIIa. The rA1 domain inhibited factor XI binding to HK, whereas the A4 peptide did not. We conclude that specific sequences exposed on the surfaces of the A1 (Val59-Lys83) and A4 (Ala317-Gly350) domains of factor XI act synergistically to promote surface-mediated factor-XI activation by factor XIIa in the presence of HK by binding factor XI to surface-bound HK (A1 domain) and by binding factor XIIa near the cleavage site (Arg369-Ile370) of factor XI (A4 domain).
Publisher
American Society of Hematology
Subject
Cell Biology,Hematology,Immunology,Biochemistry
Cited by
10 articles.
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1. Factor XI;Production of Plasma Proteins for Therapeutic Use;2012-12-14
2. Historical perspective of factor XI;Thrombosis Research;2005-01
3. Platelet Coagulation-Protein Interactions;Seminars in Thrombosis and Hemostasis;2004-08
4. Factor XI, but Not Prekallikrein, Blocks High Molecular Weight Kininogen Binding to Human Umbilical Vein Endothelial Cells;Journal of Biological Chemistry;2003-06
5. Factor XI;Wiley Encyclopedia of Molecular Medicine;2002-01-15