| Autor: |
Tish A. Young, Arne Slungaard, Nigel S. Key, Christopher A. Pennell, Arkadiusz Z. Dudek, Troy D. Decker |
| Rok vydání: |
1997 |
| Předmět: |
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| Zdroj: |
Journal of Biological Chemistry. 272:31785-31792 |
| ISSN: |
0021-9258 |
| DOI: |
10.1074/jbc.272.50.31785 |
| Popis: |
Platelet factor 4 (PF4) is an abundant platelet α-granule heparin-binding protein. We have previously shown that PF4 accelerates up to 25-fold the proteolytic conversion of protein C to activated protein C by the thrombin·thrombomodulin complex by increasing its affinity for protein C 30-fold. This stimulatory effect requires presence of the γ-carboxyglutamic acid (Gla) domain in protein C and is enhanced by the presence of a chondroitin sulfate glycosaminoglycan (GAG) domain on thrombomodulin. We hypothesized that cationic PF4 binds to both protein C and thrombomodulin through these anionic domains. Qualitative SDS-polyacrylamide gel electrophoresis analysis of avidin extracts of solutions containing biotinylated PF4 and candidate ligands shows that PF4 binds to GAG+ but not GAG− forms of thrombomodulin and native but not Gla-domainless protein C. Quantitative analysis using the surface plasmon resonance-based BIAcoreTM biosensor system confirms the extremely high affinity of PF4 for heparin (K D = 4 nm) and shows that PF4 binds to GAG+ thrombomodulin with aK D of 31 nm and to protein C with aK D of 0.37 μm. In contrast, PF4 had no measurable interaction with GAG− thrombomodulin or Gla-domainless protein C. Western blot analysis of normal human plasma extracted with biotinylated PF4 demonstrates PF4 binding to protein C in a physiologic context. Thus, PF4 binds with relative specificity and high affinity to the GAG− domain of thrombomodulin and the Gla domain of protein C. These interactions may enhance the affinity of the thrombin·thrombomodulin complex for protein C and thereby promote the generation of activated protein C. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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