Functional analysis of the EGF-like domain mutations Pro55Ser and Pro55Leu, which cause mild hemophilia B.
Author
Summary, in English
We studied the functional role of two mutations, Pro55Ser and Pro55Leu, located in the N-terminal Epidermal Growth Factor-like domain (EGF1) of coagulation factor (F) IX. Both mutations cause mild hemophilia B with habitual FIX coagulant activities of 10-12% and FIX antigen levels of 50%. We found that activation by FVIIa/TF and FXIa was normal for FIXPro55Ser, but resulted in proteolysis of FIXPro55Leu at Arg318-Ser319 with a concomitant loss of amidolytic activity, suggesting intramolecular communication between EGF1 and the serine protease domain in FIX. This was further supported by experiments using an anti-EGF1 monoclonal antibody. Activation of FX by FIXaPro55Ser was impaired in both the presence and the absence of phospholipid or FVIIIa, indicating that Pro55 is not directly involved in binding to FVIIIa. We also studied the effect of the two Pro55 mutations on Ca2+ affinity and found only small changes. Thus, the Pro55Ser mutation causes hemophilia primarily through to an impaired ability to activate FX whereas at least in vitro the Pro55Leu defect interferes with the activation of FIX.
Department/s
- Paediatric Hematologic Research Group
- Clinical Chemistry, Malmö
- Paediatric Haematology Research Unit
Publishing year
2003
Language
English
Pages
782-790
Publication/Series
Journal of Thrombosis and Haemostasis
Volume
1
Issue
4
Full text
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Links
Document type
Journal article
Publisher
Wiley-Blackwell
Topic
- Cardiac and Cardiovascular Systems
Status
Published
Research group
- Paediatric Hematologic Research Group
- Clinical Chemistry, Malmö
- Paediatric Haematology Research Unit
ISBN/ISSN/Other
- ISSN: 1538-7933