title: Cell-free phosphorylation of the murine small heat-shock protein hsp25 by an endogenous kinase from Ehrlich ascites tumor cells.
abstract: The small heat-shock protein hsp25 of the Ehrlich ascites tumor exists in one non-phosphorylated (hsp25/1) and two phosphorylated (hsp25/2, hsp25/3) isoforms. In stationary phase tumor cells, a protein kinase activity was detected which phosphorylates hsp25/1, resulting in the formation of several phosphorylated hsp25 isoforms, including those occurring naturally in the tumor. Cell-free phosphorylation of hsp25 required Mg2+ and ATP and was independent of Ca2+, phosphatidylserine, cAMP and cGMP. Polymyxin B inhibited, specifically, hsp25 phosphorylation, whereas trifluoperazine, staurosporine and the protein inhibitor of protein kinase A had no effect. In its properties, the hsp25 phosphorylating kinase differs from other common kinases such as protein kinases A and C, calcium/calmodulin-dependent kinases, and the ribosomal protein S6 kinase.
authors.affiliation: Max-Delbrück-Centrum für Molekulare Medizin, Berlin-Buch, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Benndorf
authors.forename: K
authors.initials: K
authors.lastname: Hayess
authors.forename: J
authors.initials: J
authors.lastname: Stahl
authors.forename: H
authors.initials: H
authors.lastname: Bielka
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism*; D002474:Cell-Free System; D015180:Electrophoresis, Gel, Two-Dimensional; D006360:Heat-Shock Proteins / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism; D051379:Mice; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D006360:Heat-Shock Proteins; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases; D008274:Magnesium