title: Identification of a 33-Kd protein associated with the alpha-granule membrane (GMP-33) that is expressed on the surface of activated platelets.
abstract: To identify antigens on the platelet plasma membrane that are exposed after activation, we developed a monoclonal antibody (MoAb) designated RUU-SP 1.77. The RUU-SP 1.77 antigen is present on the membrane of resting platelets at a basal level and is strongly expressed on the plasma membrane after thrombin activation. Freshly fixed platelets bound 4,150 +/- 1,935 (mean +/- SD) RUU-SP 1.77 molecules per platelet; on fixed thrombin-stimulated platelets the number of binding sites was upregulated to 19,050 +/- 5,120 (kd 4.5 +/- 0.8 nmol/L). MoAb RUU-SP 1.77 recognized a major protein of 33 Kd and a minor 28-Kd protein, both under nonreduced and reduced conditions. Immunoelectron microscopic studies showed the presence of the protein associated with the membrane of alpha-granules. Due to the localization associated with the alpha-granule membrane, we have designated it GMP-33 (granule membrane protein with a molecular weight of 33 Kd). Based on structural properties, we conclude that GMP-33 is a protein associated with the alpha-granule membrane that has not been described before.
authors.affiliation: Department of Haematology, University Hospital Utrecht, The Netherlands.
authors.forename: M J
authors.initials: MJ
authors.lastname: Metzelaar
authors.forename: H F
authors.initials: HF
authors.lastname: Heijnen
authors.forename: J J
authors.initials: JJ
authors.lastname: Sixma
authors.forename: H K
authors.initials: HK
authors.lastname: Nieuwenhuis
mesh_terms: D000911:Antibodies, Monoclonal; D000941:Antigens / Q000276:immunology; D001792:Blood Platelets / Q000737:chemistry* / Q000648:ultrastructure; D015153:Blotting, Western; D003594:Cytoplasmic Granules / Q000648:ultrastructure*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007150:Immunohistochemistry; D007425:Intracellular Membranes / Q000737:chemistry*; D008970:Molecular Weight; D015539:Platelet Activation; D010980:Platelet Membrane Glycoproteins / Q000032:analysis* / Q000737:chemistry / Q000276:immunology; D013917:Thrombin / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D000941:Antigens; D010980:Platelet Membrane Glycoproteins; D013917:Thrombin