title: T3-p28 is a protein associated with the delta and epsilon chains of the T cell receptor-T3 antigen complex during biosynthesis.
abstract: The human T cell receptor-T3 antigen complex is composed of at least five polypeptide chains. In addition to the 45-kDa/50-kDa heterodimer (alpha and beta chains) of the T cell receptor, the complex includes 25-kDa (T3-gamma) and 20-kDa (T3-delta) glycoproteins and a nonglycosylated 20-kDa (T3-epsilon) protein. Here we report that in pulse-chase biosynthetic labeling experiments we detect a new polypeptide chain (T3-p28) which is associated with the T3-delta and T3-epsilon chains during biosynthesis but not on the cell surface. T3-p28, which is not recognized by anti-T3 antibodies, can be chemically distinguished from the previously described T3-gamma chain. The carboxylic ionophore monensin blocks the apparent dissociation of T3-p28 from the T3-delta and T3-epsilon chains. Peripheral blood lymphocytes as well as all T cell leukemic lines tested contain T3-p28, except one HPB-ALL subline. Since the T3-p28 protein is only observed early in biosynthesis of T3-delta and T3-epsilon, it may function in intracellular transport or assembly of the T cell receptor-T3 complex.
mesh_terms: D000954:Antigens, Surface; D017252:CD3 Complex; D002460:Cell Line; D006801:Humans; D008565:Membrane Proteins / Q000276:immunology / Q000378:metabolism*; D008985:Monensin / Q000494:pharmacology; D011487:Protein Conformation; D011948:Receptors, Antigen, T-Cell / Q000096:biosynthesis*; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism*
chemical_list: D000954:Antigens, Surface; D017252:CD3 Complex; D008565:Membrane Proteins; D011948:Receptors, Antigen, T-Cell; D008985:Monensin