title: Inhibition of protein synthesis initiation by oxidized glutathione: activation of a protein kinase that phosphorylates the alpha subunit of eukaryotic initiation factor 2.
abstract: Oxidized glutathione (GSSG) (0.02-0.5 mM) inhibits reticulocyte lysates by a mechanism similar to that observed in heme deficiency. Incubation of hemin-supplemented postribosomal supernates with GSSG results in the activation of a translational inhibitor [I(GSSG)]. The activation of I(GSSG) is enhanced by the presence of an energy-regenerating system. The simultaneous addition of 1 mM dithiothreitol blocks the activation of the GSSG-induced inhibitor; however, once inhibitor is formed, its activity is not affected by 1 mM dithiothreitol. GSSG-treated postribosomal supernates and partially purified preparations of I(GSSG) inhibit protein synthesis in hemin-supplemented lysates with biphasic kinetics. Inhibition by I(GSSG) is blocked by cyclic AMP (2-10 mM) and is potentiated by ATP (2 mM). The inhibition is also blocked or reversed by eukaryotic initiation factor eIF-2. The activation of I(GSSG) is accompanied by an increased cyclic AMP-independent protein kinase activity which phosphorylates the 38,000-dalton component (alpha subunit) of eIF-2; however, GSSG treatment of supernates does not alter the activity of the cyclic AMP-independent protein kinase activity that phosphorylates the 49,000-dalton polypeptide component (beta subunit) of eIF-2. These data indicate that GSSG treatment of reticulocyte lysates results in the activation of a protein kinase with inhibitory and phosphorylation properties similar to those of the heme-regulated cyclic AMP-independent protein kinase which is activated in heme deficiency.
mesh_terms: D002474:Cell-Free System; D003864:Depression, Chemical; D004789:Enzyme Activation / Q000187:drug effects; D005978:Glutathione / Q000031:analogs & derivatives* / Q000494:pharmacology; D007700:Kinetics; D046911:Macromolecular Substances; D010442:Peptide Chain Initiation, Translational / Q000187:drug effects*; D010448:Peptide Initiation Factors / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D012156:Reticulocytes
chemical_list: D046911:Macromolecular Substances; D010448:Peptide Initiation Factors; D011494:Protein Kinases; D005978:Glutathione