Regulation of protein synthesis in rabbit reticulocyte lysates. Thiophosphorylation of initiation factor eIF-2 by heme-regulated protein kinase.
The heme-regulated protein kinase, which specifically phosphorylates the 38-kDa subunit of initiation factor eIF-2, can utilize adenosine 5'-O-(3-thiotriphosphate) (ATP[gamma S]) as a substrate. The rate of thiophosphorylation is 5-6-times slower than that observed with ATP. It is of special interest that thiophosphorylated derivatives of eIF-2 are resistant to dephosphorylation catalyzed by eIF-2 phosphoprotein phosphatase. The thiophosphorylated eIF-2 is less effective in promoting protein synthesis in hemin-deficient lysates under physiological conditions. In addition, ATP[gamma S] could also be utilized by the self-phosphorylation activity intrinsically associated with HRI.
D000818:Animals; D001798:Blood Proteins / Q000096:biosynthesis*; D015852:Eukaryotic Initiation Factor-2; D006418:Heme / Q000502:physiology*; D007700:Kinetics; D010448:Peptide Initiation Factors / Q000502:physiology*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D011506:Proteins / Q000502:physiology*; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000378:metabolism
D001798:Blood Proteins; D015852:Eukaryotic Initiation Factor-2; D010448:Peptide Initiation Factors; D011506:Proteins; D013438:Sulfhydryl Compounds; D006418:Heme; D011494:Protein Kinases; D010749:Phosphoprotein Phosphatases