title: The interferon-induced protein kinase PK-i from mouse L cells.
abstract: Interferon-treated L cells are characterized by an increased protein kinase activity that can selectively phosphorylate the small subunit of eukaryotic initiation factor 2. This protein kinase, PK-i, has been extensively purified and shown to be a potent inhibitor of mRNA translation. The purified PK-i contains the endogenously phosphorylated 67,000 Mr protein characteristic of interferon-treated cell extracts. PK-i can also phosphorylate arginine-rich histones. Purified PK-i can be activated by preincubation with ATP (but not adenylyl imidodiphosphate) and low concentrations of double-stranded RNA. The activation results in an increase in the first rate of eIF-2 phosphorylation. Activated PK-i becomes resistant to high concentrations of double-stranded RNA and more thermostable. A stimulator of PK-i activity, factor A, was isolated, as well as a specific phosphoprotein phosphatase that dephosphorylates the 67,000 Mr protein and eIF-2. These two factors, which are present in untreated L cells, may regulate the translation inhibitory activity of the interferon-induced and double-stranded RNA-activated protein kinase PK-i.
mesh_terms: D000818:Animals; D004789:Enzyme Activation; D007372:Interferons / Q000494:pharmacology*; D007700:Kinetics; D007739:L Cells / Q000187:drug effects / Q000201:enzymology; D051379:Mice; D008970:Molecular Weight; D010445:Peptide Elongation Factors / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism*
chemical_list: D010445:Peptide Elongation Factors; D007372:Interferons; D011494:Protein Kinases; D010749:Phosphoprotein Phosphatases