Autor: |
A V, Bendetowicz, J A, Morris, R J, Wise, G E, Gilbert, R J, Kaufman |
Rok vydání: |
1998 |
Předmět: |
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Zdroj: |
Blood. 92(2) |
ISSN: |
0006-4971 |
Popis: |
von Willebrand factor (vWF) is a multimeric adhesive glycoprotein with one factor VIII binding site/subunit. Prior reports suggest that posttranslational modifications of vWF, including formation of N-terminal intersubunit disulfide bonds and subsequent cleavage of the propeptide, influence availability and/or affinity of factor VIII binding sites. We found that deletion of the vWF propeptide produced a dimeric vWF molecule lacking N-terminal intersubunit disulfide bonds. This molecule bound fluorescein-labeled factor VIII with sixfold lower affinity than multimeric vWF in an equilibrium flow cytometry assay (approximate KDs, 5 nmol/L v 0.9 nmol/L). Coexpression of propeptide-deleted vWF with the vWF propeptide in trans yielded multimeric vWF that displayed increased affinity for factor VIII. Insertion of an alanine residue at the N-terminus of the mature vWF subunit destroyed binding to factor VIII, indicating that the native mature N-terminus is required for factor VIII binding. The requirement for vWF propeptide cleavage was shown by (1) a point mutation of the vWF propeptide cleavage site yielding pro-vWF that was defective in factor VIII binding and (2) correlation between efficiency of intracellular propeptide cleavage and factor VIII binding. Furthermore, in a cell-free system, addition of the propeptide-cleaving enzyme PACE/furin enabled factor VIII binding in parallel with propeptide cleavage. Our results indicate that high-affinity factor VIII binding sites are located on N-terminal disulfide-linked vWF subunits from which the propeptide has been cleaved. |
Databáze: |
OpenAIRE |
Externí odkaz: |
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