title: Protein kinase activity of the intracellular but not of the membrane-associated form of the Ki-1 antigen (CD30).
abstract: The Hodgkin-associated Ki-1 antigen (CD30) consists of a 120-kDa membrane-associated glycosylated phosphoprotein (Ki-1/120) and a 57-kDa non-glycosylated phosphoprotein (Ki-1/57) which only occurs intracellularly. Both molecules are phosphorylated at serine residues. An analysis of the peptide fragments resulting from staphylococcal V8-protease digestion of the Ki-1/57 molecule revealed identical bands irrespective of the cell source. Only a few bands of the Ki-1/57 digests appeared among the peptide fragments of the Ki-1/120 membrane antigen. The protein kinase activity was tested for both forms of the Ki-1 antigen. The Ki-1/120, devoid of the Ki-1/57 molecule, was immunoprecipitated from cell lysates of Hodgkin-analogous cell lines L428 or L540, which had been loaded with the Ki-1 or the Ki-1-analogous antibodies Ber-H2, HSR-1, -2 and -3 (method 1). These other antibodies reacted with the Ki-1/120, but not with the Ki-1/57 antigen. The latter, devoid of the Ki-1/120, was isolated from L540 cells after removal of the membrane form by method 1 or from U266/Bl myeloma or Raji Burkitt lymphoma cells which only contain the smaller form. Effects of non-specific adsorption were eliminated by various control precipitates. The Ki-1/57 intracellular antigen showed autophosphorylation and could phosphorylate histones as well. In contrast, a protein kinase activity of the membrane-associated Ki-1/120 could not be demonstrated.
authors.affiliation: Biochemisches Institut der Medizinischen Fakultät der Christian-Albrechts-Universität zu Kiel, FRG.
authors.forename: H
authors.initials: H
authors.lastname: Hansen
authors.forename: G
authors.initials: G
authors.lastname: Bredfeldt
authors.forename: B
authors.initials: B
authors.lastname: Havsteen
authors.forename: H
authors.initials: H
authors.lastname: Lemke
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000943:Antigens, Differentiation / Q000378:metabolism*; D000951:Antigens, Neoplasm / Q000378:metabolism*; D000954:Antigens, Surface / Q000378:metabolism; D003593:Cytoplasm / Q000201:enzymology; D015180:Electrophoresis, Gel, Two-Dimensional; D006657:Histones / Q000378:metabolism; D006689:Hodgkin Disease / Q000378:metabolism; D006801:Humans; D017730:Ki-1 Antigen; D010446:Peptide Fragments / Q000032:analysis; D010766:Phosphorylation; D011494:Protein Kinases; D014407:Tumor Cells, Cultured
chemical_list: D000596:Amino Acids; D000943:Antigens, Differentiation; D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D006657:Histones; D017730:Ki-1 Antigen; D010446:Peptide Fragments; D011494:Protein Kinases