title: A protein kinase of the plasma membrane of Dictyostelium discoideum.
abstract: D. discoideum amoebae were found to phosphorylate plasma membrane proteins when intact cells were incubated with either [gamma-32P]ATP or [32P]phosphate. In the first case, the incorporation was largely a consequence of the hydrolysis of [gamma-32P]ATP, cellular uptake of the generated [32P]phosphate and its subsequent incorporation into ATP. When the contribution of this process to the phosphorylating activity of intact cells was eliminated, an ecto-protein kinase (ATP: protein phosphotransferase, EC 2.7.1.37) activity could be demonstrated. As amoebae progressed through their aggregation program, they showed a decreased ability to phosphorylate their plasma membrane when incubated with [gamma-32 P]ATP or [32P]phosphate. Analysis of ATPase activity, permeability properties and the pattern of proteins phosphorylated by intact cells and isolated plasma membranes lead to the following conclusions: the lower levels of phosphorylation observed with starved cells reflected an altered uptake of [32P]phosphate by these cells rather than a significant change in the plasma membrane protein kinase activity. Neither the substrates nor the activity of the ecto-protein kinase was dramatically altered during starvation.
mesh_terms: D002462:Cell Membrane / Q000201:enzymology; D004023:Dictyostelium / Q000201:enzymology*; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism; D008970:Molecular Weight; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D011494:Protein Kinases