title: Binding of 125I-labelled fibrin(ogen) fragments to platelets and to immunoprecipitated glycoprotein IIb-IIIa complex.
abstract: To further investigate which parts of the fibrinogen molecule that are responsible for its binding to the fibrinogen receptor on human platelets, the following approaches were made: The glycoprotein IIb-IIIa complex (the putative fibrinogen receptor) was immunoprecipitated in crossed immunoelectrophoresis of Triton X-100-extracts of platelets against antibodies to whole platelet proteins. Subsequently, the immunoplates were incubated with 125I-labelled, plasmin- or CNBr-cleaved fibrinogen fragments (pre-X,X,Y,D,Degta,Efg,N-DSK) or fibrin fragments (E1,N-dsk), characterized by partial sequenation. The immunoplates were exposed to X-ray films, and binding of the fragments to the glycoprotein IIb-IIIa complex was examined. The findings were compared to the results obtained from studies on binding of the same fragments to intact gel-filtered platelets after ADP-stimulation. The following conclusions were made: All fragments except Efg and Degta bound to the immunoprecipitated GPIIb-IIIa complex as well as to ADP-stimulated platelets suggesting that at least two sequences in the E domain and one in each of the D domains of fibrinogen are involved in binding to the platelet receptor. The GPIIb-IIIa complex is the only surface-located platelet antigen that binds fibrinogen and the aforementioned fragments. The binding of the fragments to the receptor is dependent on divalent cations.
mesh_terms: D000906:Antibodies; D001345:Autoradiography; D001792:Blood Platelets / Q000032:analysis / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure; D002850:Chromatography, Gel; D003488:Cyanogen Bromide / Q000494:pharmacology; D000939:Epitopes / Q000276:immunology; D005338:Fibrin Fibrinogen Degradation Products / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D005341:Fibrinolysin / Q000494:pharmacology; D006801:Humans; D007123:Immunoelectrophoresis, Two-Dimensional; D007457:Iodine Radioisotopes; D010980:Platelet Membrane Glycoproteins; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000276:immunology / Q000378:metabolism*
chemical_list: D000906:Antibodies; D000939:Epitopes; D005338:Fibrin Fibrinogen Degradation Products; D007457:Iodine Radioisotopes; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; D005341:Fibrinolysin; D003488:Cyanogen Bromide