The factor IX phospholipid-binding site is required for calcium-dependent activation of factor IX by factor XIa.
نویسندگان
چکیده
To determine the functional role of the metal-dependent conformational changes in Factor IX, two populations of conformation-specific anti-Factor IX antibodies were prepared. Anti-Factor IX X Mg(II) antibodies bind to Factor IX in the presence of Mg(II) and other metal ions, but not in the absence of metal ions. Anti-Factor IX X Ca(II)-specific antibodies bind to Factor IX in the presence of Ca(II) and Sr(II), but not in the presence of Mn(II), Mg(II), and Ba(II). In the presence of a metal ion that induces the conformational transition recognized by the anti-Factor IX X Mg(II) antibodies, the concentrations of CaCl2 and SrCl2 needed for the half-maximal binding of the anti-Factor IX X Ca(II)-specific antibodies to Factor IX were reduced 3- and 20-fold, respectively. Factor IX binding to phospholipid vesicles was inhibited by the Fab fragments of the anti-Factor IX X Ca(II)-specific antibodies, but was not inhibited by the Fab fragments of the anti-Factor IX X Mg(II) antibodies. Factor XIa activation of Factor IX was also inhibited by the Fab fragments of the anti-Factor IX X Ca(II)-specific antibodies, but not by the anti-Factor IX X Mg(II) antibodies. These results support the hypothesis that Factor IX undergoes two metal-dependent conformational transitions: FIX----FIX'----FIX*. The first transition (FIX----FIX') is metal-dependent but cation-nonselective; the second transition (FIX'----FIX*) is metal-selective for Ca(II) or Sr(II). The second transition results in the expression of conformational determinants necessary for membrane binding and the Ca(II)-dependent activation of Factor IX by Factor XIa. These results suggest chemical similarity between a surface of a domain of Factor XIa and phospholipid vesicles, both of which interact with Factor IX in the presence of Ca(II).
منابع مشابه
Structure, function, and molecular defects of factor IX.
A CROSS 1 3 generations and 55 affected members, the “bleeders of Tenna” in eastern Switzerland have demonstrated that hemophilia B is not necessarily severe or associated with spontaneous bleeding episodes.’ Moreover, patients with congenitally deficient factor IX activity are clinically indistinguishable from those with factor VIII deficiency, that is, hemophilia A. Both types of hemophilia a...
متن کاملModification of the N-terminus of human factor IX by defective propeptide cleavage or acetylation results in a destabilized calcium-induced conformation: effects on phospholipid binding and activation by factor XIa.
The propeptide of human coagulation factor IX (FIX) directs the gamma-carboxylation of the first 12 glutamic acid residues of the mature protein into gamma-carboxyglutamic acid (Gla) residues. The propeptide is normally removed before secretion of FIX into the blood. However, mutation of Arg-4 in the propeptide abolishes propeptide cleavage and results in circulating profactor IX in the blood. ...
متن کاملCleavage and activation of human factor IX by serine proteases.
Human factor IX circulates as a single-chain glycoprotein. Upon activation in vitro, it is cleaved into disulfide-linked light and heavy chains and an activation peptide. After reduction of activated 125I-factor IX, the heavy and light chains are readily identified by gel electrophoresis. A direct, immunoradiometric assay for factor IXa was developed to assess activation of factor IX for protea...
متن کاملActivation of factor IX bound to cultured bovine aortic endothelial cells.
Previous studies have shown that factor IX and its activated form, factor IXa, bind to cultured vascular endothelial cells and that cell-bound factor IXa retains its procoagulant activity. The present studies provide evidence that factor IX bound to cultured bovine aortic endothelial cells can be activated. Factor IX activation was assessed by finding cleavage of the factor IX molecule on NaDod...
متن کاملFunctional domains in the heavy-chain region of factor XI: a high molecular weight kininogen-binding site and a substrate-binding site for factor IX.
To probe the molecular interactions of factor XI we have prepared two monoclonal antibodies (MoAbs; 5F7 and 3C1), each of which binds the heavy chain of reduced and alkylated factor XIa. Competitive solid phase radioimmunoassay (RIA) binding studies revealed that 5F7 and 3C1 are directed against different epitopes within factor XI. One antibody (5F7) blocked the surface-mediated proteolytic act...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- The Journal of biological chemistry
دوره 262 16 شماره
صفحات -
تاریخ انتشار 1987