title: Indirect inactivation of eukaryotic initiation factor 2 in reticulocyte lysate by selenite.
abstract: Addition of selenite to rabbit reticulocyte lysate produces a biphasic pattern of translational inhibition. Sucrose density gradient shows that the onset of translational inhibition is accompanied by decreased Met-tRNAf binding to 43 SN ribosomal subunits and loss of polysomes. Control rates of translation are restored by the addition of exogenous eukaryotic initiation factor 2 (eIF-2). Selenite also directly inhibits Met-tRNAf binding activity of eIF-2. While selenite could react directly with unpaired cysteine residues of eIF-2 to inhibit protein synthesis initiation, a more complex mechanism than a direct inactivation of eIF-2 is suggested by the following observations: 1) translational inhibition produced by selenite is accompanied by an apparent increase in the phosphorylation state of eIF-2alpha; and 2) the extent of translational inhibiton is not proportional to steady-state level of phosphorylation. Rather, the time required for the onset of translational inhibition decreases as the level of eIF-2alpha phosphorylation is increased. This suggests a multistep sequence for eIF-2 inactivation, dependent upon an initial activation of eIF-2alpha kinase and followed by additional eIF-2 modification(s).
mesh_terms: D000818:Animals; D005033:Ethylmaleimide / Q000494:pharmacology; D015852:Eukaryotic Initiation Factor-2; D005978:Glutathione / Q000494:pharmacology; D007700:Kinetics; D008626:Mercuribenzoates / Q000494:pharmacology; D010445:Peptide Elongation Factors / Q000302:isolation & purification; D010448:Peptide Initiation Factors / Q000037:antagonists & inhibitors* / Q000302:isolation & purification; D014176:Protein Biosynthesis / Q000187:drug effects*; D011506:Proteins / Q000037:antagonists & inhibitors* / Q000302:isolation & purification; D012343:RNA, Transfer / Q000378:metabolism; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D020887:Selenious Acid; D012643:Selenium / Q000494:pharmacology*
chemical_list: D015852:Eukaryotic Initiation Factor-2; D008626:Mercuribenzoates; D010445:Peptide Elongation Factors; D010448:Peptide Initiation Factors; D011506:Proteins; D012343:RNA, Transfer; D020887:Selenious Acid; D005978:Glutathione; D012643:Selenium; D005033:Ethylmaleimide