Phosphorylation of eukaryotic protein synthesis initiation factors.
Phosphorylation of eukaryotic initiation factors was examined both in intact cells and in vitro with purified components. Intact rabbit reticulocytes were incubated in a medium containing[32P]phosphate, and eight initiation factors were isolated and partially purified. The purified factors were analyzed on dodecyl sulfate/polyacrylamide gels and compared with highly purified nonradioactive factors. Significant amounts of radioactivity were found associated with initiation factors eIF-2, polypeptide 2 (molecular weight 53,000); eIF-3, polypeptides 2 and 4 (molecular weights 110,000 and 67,000); and eIF-4B. Purfied initiation factors from rabbit reticulocytes were also treated in vitro with [gamma-32P]ATP and a cyclic AMP-independent protein kinase isolated from rabbit erythrocytes. Only the factor polypeptides phosphorylated intracellularly were phosphorylated in vitro. The results suggest that the cyclic AMP-independent protein kinase is responsible for the phosphorylation of specific initiation factors in cells active in protein synthesis and that it may play a role in regulating translation.
D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D008970:Molecular Weight; D010448:Peptide Initiation Factors; D010750:Phosphoproteins / Q000097:blood / Q000378:metabolism*; D011494:Protein Kinases / Q000097:blood / Q000378:metabolism; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism
D010448:Peptide Initiation Factors; D010750:Phosphoproteins; D011494:Protein Kinases
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