Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0019087 (hemorrhagic diathesis)
 678 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The assembly of the tenase complex on the surface of the platelet is an essential step in maintaining normal hemostasis as evidenced by the serious hemorrhagic diathesis associated with either factor IX (FIX) or factor VIII deficiencies. Understanding the regions and or residues of FIX crucial for proper binding to platelets has important clinical implications. The ability of FIX to bind activated platelets in the presence of 4 mmol/l CaCl2 was examined using electrophoretic light-scattering experiments. Wild-type FIX binds to activated platelets with dissociation constant Kd = 7.9 nmol/l. Activated FIX binds to activated platelets with Kd = 2 nmol/l. Activated factor VII does not bind activated platelets at physiological concentrations. The Gla domain of FIX is important for the binding of FIX to activated platelets since a chimera with a factor VII (FVII) template and FIX Gla [FVII(FIXGla)] has Kd = 9.6 nmol/l, and a chimera with a FVII template and FIX Gla, A and the first epidermal growth factor domain (EGF1) [FVII(FIXGla,A,EGF1)] has Kd = 9.7 nmol/l, but a chimera with a FIX template and a FVII Gla [FIX(FVIIGla)] does not bind activated platelets. Altering the fifth residue of FIX from a lysine to an alanine (Lys5<--Ala) abolishes the mutant from binding to collagen but does not affect FIX binding to the activated platelet (Kd = 9.8 nmol/l). Point mutations involved with residues 4 and 5 (Gly4<--Phe and Lys5<--no residue), residue 9 (Phe9<--Ala), residue 10 (Val10<--Lys) and residues 9-11 (Phe9<--Met, Val10<--Lys, Glu11<--Lys) do not bind to activated platelets.
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PMID:Location of the platelet binding site in zymogen coagulation factor IX. 1146 6

Reported evidence of a role in fibrinolysis by fibrinopeptide (Fp)B-dependent intermolecular fibrin polymerization contacts and of reversed FpA/FpB release sequence from fibrinogen Kingsport led us to investigate the fibrinolytic properties of Kingsport clots. Clot lysis was induced by either plasmin (pH 7.4) or by a mixture of plasminogen and recombinant tissue plasminogen activator and measured by lysis time and by turbidity (350 nm) time course. Clots were formed by thrombin from plasminogen-free fibrinogen (pH 7.4, 8 mmol/l CaCl2), with or without 40 nmol/l factor XIII or 20% afibrinogenemic plasma. Displaying no differences from corresponding normal controls were (a) lysis of repolymerized fibrin clots, and (b) chromogenic measurements of fibrin-stimulated Glu-plasminogen activation by recombinant tissue plasminogen activator. By contrast, thrombin-induced fine and coarse network clots (n = 7) displayed faster turbidity loss than corresponding normal controls and shorter lysis times ranging 31-55% of controls. Comparison of clots of fibrinogen fractions lacking approximately 90% of their alpha chain carboxyl terminal regions, n = 2, also displayed faster plasmin-induced lysis than corresponding controls. To assess the role of FpB release-dependent intermolecular polymerization contacts, clots were prepared in the presence of three molar excess antibeta 15-42 immunoglobulin G, n = 2, and displayed no differences in plasmin-induced lysis from nonimmune immunoglobulin G controls. The reversed FpA/FpB release sequence from Kingsport fibrinogen resulted in clots with decreased resistance to plasmin. We suggest that both markedly slow polymerization and decreased plasmin resistance played causative roles in the hemorrhagic diathesis associated with this dysfibrinogen.
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PMID:Decreased plasmin resistance by clots of a homophenotypic Aalpha R 16H fibrinogen (Kingsport, slower fibrinopeptide A than fibrinopeptide B release). 2001 99