title: Ecto-protein kinase activities in normal and transformed cells.
abstract: The incubation of intact uninfected and Rous sarcoma virus (RSV)-transformed chicken cells (SR-RSV-A) with micromolar amounts of [gamma-32P]ATP under physiological conditions resulted in the radioactive phosphorylation of a variety of proteins. According to the experimental protocol the detectable phosphorylation was restricted to ATP utilization at the cell surface and was catalyzed by surface located protein kinase (PK). Serine- and to a lesser extent, threonine residues were phosphorylated. With respect to this enzyme the cells under investigation showed upon incubation with phosvitin the release of surface (phosvitin) kinase into the incubation medium. Based on immunochemical analysis and PK-assays using antisera from RSV-tumor bearing rabbits (TBR-serum) the pp60v-src with its associated tyrosine kinase activity was likewise detected in appreciable amounts at the outside of RSV-transformed chicken and mammalian cells. There was no cross reactivity of TBR-serum with phosvitin kinase. Phosvitin was not phosphorylated by the immunoprecipitated pp60v-src. Whereas phosphorylation catalyzed by pp60v-src was blocked with 10 to 20 microM diadenosine 5',5''-P1P4 tetraphosphate (Ap4A) the phosvitin phosphorylation was far less sensitive towards inhibition by Ap4A, similar to the cellular pp60c-src kinase activity in uninfected cells. The functional significance of the PK activities in uninfected and RSV-transformed cells observed at their surface or in cell-free form as well as the nature of their substrates remain to be established.
mesh_terms: D000227:Adenine Nucleotides / Q000494:pharmacology; D000818:Animals; D001358:Avian Sarcoma Viruses; D002462:Cell Membrane / Q000201:enzymology; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D002642:Chick Embryo; D003470:Culture Media / Q000032:analysis; D015226:Dinucleoside Phosphates; D004591:Electrophoresis, Polyacrylamide Gel; D008565:Membrane Proteins / Q000032:analysis; D010750:Phosphoproteins / Q000032:analysis; D010766:Phosphorylation; D011233:Precipitin Tests; D011494:Protein Kinases / Q000378:metabolism*; D013347:Subcellular Fractions / Q000201:enzymology; D013997:Time Factors
chemical_list: D000227:Adenine Nucleotides; D003470:Culture Media; D015226:Dinucleoside Phosphates; D008565:Membrane Proteins; D010750:Phosphoproteins; C020733:diadenosine tetraphosphate; D011494:Protein Kinases; C034454:ectoprotein kinase