title: Reconstitution of the purified platelet fibrinogen receptor. Fibrinogen binding properties of the glycoprotein IIb-IIIa complex.
abstract: Several lines of evidence indicate that the platelet membrane glycoprotein IIb-IIIa complex (GP IIb-IIIa) is necessary for the expression of platelet fibrinogen receptors. The purpose of the present study was to determine whether purified GP IIb-IIIa retains the properties of the fibrinogen receptor on platelets. Glycoprotein IIb-IIIa was incorporated by detergent dialysis into phospholipid vesicles composed of 30% phosphatidylcholine and 70% phosphatidylserine. 125I-Fibrinogen binding to the GP IIb-IIIa vesicles, as measured by filtration, had many of the characteristics of 125I-fibrinogen binding to whole platelets or isolated platelet plasma membranes: binding was specific, saturable, reversible, time dependent, and Ca2+ dependent. The apparent dissociation constant for 125I-fibrinogen binding to GP IIb-IIIa vesicles was 15 nM, and the maximal binding capacity was 0.1 mol of 125I-fibrinogen/mol of GP IIb-IIIa. 125I-Fibrinogen binding was inhibited by amino sugars, the GP IIb and/or IIIa monoclonal antibody 10E5, and the decapeptide from the carboxyl terminus of the fibrinogen gamma chain. Furthermore, little or no 125I-fibrinogen bound to phospholipid vesicles lacking protein or containing proteins other than GP IIb-IIIa (i.e. bacteriorhodopsin, apolipoprotein A-I, or glycophorin). Also, other 125I-labeled plasma proteins (transferrin, orosomucoid) did not bind to the GP IIb-IIIa vesicles. These results demonstrate that GP IIb-IIIa contains the platelet fibrinogen receptor.
authors.forename: L V
authors.initials: LV
authors.lastname: Parise
authors.forename: D R
authors.initials: DR
authors.lastname: Phillips
mesh_terms: D000596:Amino Acids / Q000494:pharmacology; D001792:Blood Platelets / Q000378:metabolism*; D002241:Carbohydrates / Q000494:pharmacology; D005340:Fibrinogen / Q000302:isolation & purification / Q000378:metabolism*; D006023:Glycoproteins / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008081:Liposomes; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism*; D010980:Platelet Membrane Glycoproteins; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D002241:Carbohydrates; D006023:Glycoproteins; D008081:Liposomes; D008565:Membrane Proteins; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; D005340:Fibrinogen