Factor IX Niigata is a mutant factor IX responsible for the moderately severe hemophilia B in a patient who has a normal level of factor IX antigen with reduced clotting activity (1- 4% of normal). We reported previously that the purified mutant protein could be converted to the factor IXaβ form by factor XIa/Ca2+ at a rate similar to that in the case of normal factor IX, but the resulting mutant factor IXaβ could not activate factor X in the presence of factor VIII, Ca2+ and phospholipids (Yoshioka, A. et al. (1986) Thromb. Res. 42, 595-604). In the present study, we analyzed factor IX Niigata at the structural level to elucidate the molecular abnormality responsible for the loss of clotting activity. Amino acid sequence analysis of a peptide obtained on lysyl endopeptidase digestion, coupled with subsequent SP-V8 digestion, demonstrated that the alanine at position 390 was substituted by valine in the catalytic domain of the factor IX Niigata molecule.
|Number of pages||3|
|Journal||Journal of biochemistry|
|Publication status||Published - Dec 1988|
All Science Journal Classification (ASJC) codes
- Molecular Biology