title: Phosphorothioated binary complex of eukaryotic initiation factor eIF-2 and GDP inhibits protein synthesis in hemin-supplemented reticulocyte lysates.
abstract: The rabbit reticulocyte heme-regulated eIF-2 alpha kinase (HRI) utilizes adenosine-5'-0-(3-thiotriphosphate) (ATP-gamma-S) as a substrate for its autophosphorylation and activation, and for the phosphorylation of eIF-2. The phosphorothioated binary complex [eIF-2(alpha-[35S]P) . GDP], interacted with the reticulocyte reversing factor (RF) in in vitro assays, and inhibited the ability of RF to catalyze GDP exchange from (eIF-2 . [3H]GDP) complexes. The phosphorothioate residue in the binary complex was resistant to phosphatase action under protein synthesis conditions. eIF-2(alpha-[35S]P) . GDP inhibited protein synthesis in hemin-supplemented lysates with biphasic kinetics, but had no effect on protein synthesis in heme-deficient lysates. The data reported here indicate that phosphorylation of eIF-2 . GDP alone, through the ability of eIF-2(alpha-P) . GDP to bind and sequester RF, is sufficient to inhibit protein chain initiation in the reticulocyte lysate.
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D000818:Animals; D004789:Enzyme Activation; D015852:Eukaryotic Initiation Factor-2; D006150:Guanine Nucleotides / Q000494:pharmacology*; D006153:Guanosine Diphosphate / Q000494:pharmacology*; D006418:Heme / Q000031:analogs & derivatives*; D006427:Hemin / Q000494:pharmacology*; D007700:Kinetics; D010448:Peptide Initiation Factors / Q000378:metabolism* / Q000494:pharmacology; D010766:Phosphorylation; D014176:Protein Biosynthesis; D011494:Protein Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism* / Q000494:pharmacology; D011817:Rabbits; D012156:Reticulocytes / Q000187:drug effects / Q000378:metabolism*; D019892:eIF-2 Kinase
chemical_list: D015852:Eukaryotic Initiation Factor-2; D006150:Guanine Nucleotides; D010448:Peptide Initiation Factors; D011506:Proteins; D006153:Guanosine Diphosphate; C022571:adenosine 5'-O-(3-thiotriphosphate); D006418:Heme; D006427:Hemin; D000255:Adenosine Triphosphate; D011494:Protein Kinases; D019892:eIF-2 Kinase