title: A serine protease (CCP1) is sequestered in the cytoplasmic granules of cytotoxic T lymphocytes.
abstract: Based upon the use of a new predictive algorithm, three peptides were synthesized that correspond to likely antigenic sites of the cytotoxic T cell-specific protease cytotoxic cell protein 1 (CCP1). Antibodies raised against these peptides, under reducing conditions, bound to a single protein of m.w. 29,000 found in two actively cytotoxic T cells. This protein was absent from a "cytotoxic" T cell line that had lost its cytolytic properties. By using immunocytologic techniques, the protein was localized within cytoplasmic granules. In addition, granules purified from the cytoplasm of cytotoxic T cells were shown, by Western blot analysis, to contain the protein. The molecule detected by the antibodies behaves, upon reduction, similarly to a diisopropylfluorophosphate-binding protein. Thus, here we provide evidence that CCP1, a protein whose expression correlates with cytotoxicity, is contained within organelles which have been implicated in killing. These findings strongly suggest that CCP1 plays a key role in T cell-mediated target cell lysis.
mesh_terms: D002460:Cell Line; D003594:Cytoplasmic Granules / Q000201:enzymology*; D003602:Cytotoxicity, Immunologic; D000939:Epitopes / Q000138:chemical synthesis / Q000276:immunology; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000276:immunology; D012697:Serine Endopeptidases / Q000032:analysis* / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000201:enzymology* / Q000648:ultrastructure
chemical_list: D000939:Epitopes; D010446:Peptide Fragments; D012697:Serine Endopeptidases