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Collagen-binding domain within bovine propolypeptide of von Willebrand factor
J Takagi1, T Fujisawa, F Sekiya
1Department of Biological Sciences, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Japan.
Abstract:
Two reduced/alkylated fragments of bovine propolypeptide of von Willebrand factor (pp-vWF) that inhibit pp-vWF binding to collagen were isolated. One is a tryptic fragment of molecular mass of about 30 kDa and inhibits the binding at a molar concentration about 20 times higher than the intact pp-vWF. Amino acid sequence of this fragment was determined almost completely, and it was revealed that this fragment corresponded to the carboxyl-terminal region of pp-vWF molecule beginning with Phe557. The other active fragment was obtained by lysyl endopeptidase digestion. This migrated as a 21.5/21-kDa doublet in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, but deglycosylation of this doublet resulted in production of single species of 19 kDa. The difference between the doublet constituents, therefore, was of carbohydrate composition. The extent of inhibition of collagen-binding by this 21.5/21-kDa fragment was comparable to that of the 30-kDa fragment, and furthermore, location of this fragment in the molecule was established to be between Phe570 and Lys682. These were the only fragments among those obtained by proteolytic digestions that had significant competitive effect on the binding of intact pp-vWF to collagen. These results strongly suggest that at least one collagen-binding site should be present in the carboxyl-terminal region of bovine pp-vWF extending from residue 570 to 682.
Insights
Researchers identified two bovine propolypeptide of von Willebrand factor (pp-vWF) fragments that inhibit collagen binding. These fragments suggest a collagen-binding site exists in the pp-vWF carboxyl-terminal region.
Area of Science:
- Biochemistry
- Molecular Biology
- Hematology
Background:
- The von Willebrand factor (vWF) plays a crucial role in primary hemostasis by mediating platelet adhesion and aggregation.
- Understanding the specific domains of vWF responsible for collagen binding is essential for elucidating its function in hemostasis and thrombosis.
Purpose of the Study:
- To identify and characterize fragments of bovine propolypeptide of von Willebrand factor (pp-vWF) that inhibit its binding to collagen.
- To determine the location of collagen-binding sites within the pp-vWF molecule.
Main Methods:
- Proteolytic digestion (tryptic and lysyl endopeptidase) of reduced/alkylated bovine pp-vWF.
- Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to analyze fragment sizes.
- Deglycosylation to assess the nature of fragment heterogeneity.
- Amino acid sequencing to determine fragment identity and location.
Main Results:
- Two pp-vWF fragments, a 30 kDa tryptic fragment (Phe557-C-terminus) and a 21.5/21 kDa lysyl endopeptidase fragment (Phe570-Lys682), were isolated.
- Both fragments significantly inhibited pp-vWF binding to collagen.
- The 21.5/21 kDa fragment's heterogeneity was attributed to carbohydrate composition.
Conclusions:
- The carboxyl-terminal region of bovine pp-vWF, specifically between residues 570 and 682, contains at least one collagen-binding site.
- These findings contribute to a detailed understanding of vWF-collagen interactions in hemostasis.