Heat-stable translational inhibitor from rabbit reticulocyte lysates.
We have purified to apparent homogeneity a heat-stable (HS) factor from the postribosomal supernatant of rabbit reticulocyte lysates [(1988) FEBS Lett. 236, 479-483]. HS inhibits translation in hemin-supplemented lysates and induces phosphorylation of the alpha-subunit of the eukaryotic initiation factor 2 as does hemin deficiency. The translational inhibition produced by addition of HS to hemin-containing reticulocyte lysates and the accompanying phosphorylation of the eIF-2 alpha subunit can be prevented or reversed by NADPH generators including glucose 6-phosphate, NADPH itself, and also by dithiols, e.g., dithiothreitol, but not by fructose 1,6-bisphosphate or by monothiols, e.g., 2-mercaptoethanol. When added to crude preparations of the proinhibitor form (proHCI) of the heme-controlled translational inhibitor (HCI), HS produces a pronounced increase of the HCI to proHCI ratio. It appeared possible that HS might be oxidized glutathione (GSSG) but this is not the case, for HS is not a substrate for highly purified glutathione reductase from rabbit erythrocytes. The spectral analysis of highly purified HS is consistent with the idea that HS could be a nucleotide derivative.
Gaitero
F
F
Centro de Biología Molecular (CSIC-UAM), Universidad Autónoma, Madrid, Spain.
Mendez
E
E
de Haro
C
C
D000818:Animals; D004229:Dithiothreitol / Q000494:pharmacology; D004789:Enzyme Activation; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D005978:Glutathione / Q000494:pharmacology; D006427:Hemin / Q000378:metabolism; D006358:Hot Temperature; D066298:In Vitro Techniques; D009249:NADP / Q000378:metabolism; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000187:drug effects*; D011494:Protein Kinases / Q000378:metabolism*; D011817:Rabbits; D012156:Reticulocytes / Q000032:analysis*; D013438:Sulfhydryl Compounds; D019892:eIF-2 Kinase
D015852:Eukaryotic Initiation Factor-2; D013438:Sulfhydryl Compounds; D009249:NADP; D006427:Hemin; D011494:Protein Kinases; D019892:eIF-2 Kinase; D005978:Glutathione; D004229:Dithiothreitol