title: Platelets contain proteins immunologically related to red cell spectrin and protein 4.1.
abstract: Human platelets were tested for the presence of proteins immunologically cross-reactive with red cell spectrin and protein 4.1. As assessed by indirect immunofluorescence microscopy, platelets were specifically reactive with affinity-purified rabbit antisera against red cell spectrin and protein 4.1. The immunoreactive platelet constituents were further analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, followed by electrophoretic transfer to nitrocellulose paper and immunoperoxidase staining. We found that whole platelets, membranes, and cytoskeletal preparations isolated by Triton X-100 extraction contain small amounts of proteins reacting with anti-spectrin or anti-protein 4.1 antiserum. The immunoreactive spectrin-like platelet protein has an apparent molecular weight of 240,000 and comigrates with the alpha-subunit of red cell spectrin. The major immunoreactive protein 4.1-like constituent has an apparent molecular weight of 78,000, which is slightly less than that of red cell protein 4.1. We conclude that platelets contain a spectrin-like protein which, by analogy with red cell spectrin, may have a role in membrane-cytoskeletal attachment. The properties and function of the platelet protein 4.1-like constituent are not yet known.
mesh_terms: D001792:Blood Platelets / Q000032:analysis / Q000276:immunology*; D001798:Blood Proteins / Q000032:analysis / Q000276:immunology*; D003598:Cytoskeletal Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D004910:Erythrocyte Membrane / Q000032:analysis / Q000276:immunology; D004912:Erythrocytes / Q000032:analysis; D005455:Fluorescent Antibody Technique; D006801:Humans; D007962:Leukocytes / Q000032:analysis; D008565:Membrane Proteins / Q000097:blood / Q000276:immunology*; D009479:Neuropeptides; D012967:Sodium Dodecyl Sulfate; D013049:Spectrin / Q000032:analysis / Q000276:immunology*
chemical_list: D001798:Blood Proteins; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D009479:Neuropeptides; C028841:erythrocyte membrane band 4.1 protein; C120557:erythrocyte membrane protein band 4.1-like 1; D013049:Spectrin; D012967:Sodium Dodecyl Sulfate