Phosphorylation in vitro of eukaryotic initiation factors IF-E2 and IF-E3 by protein kinases

O G Issinger, R Benne, J W Hershey, R R Traut

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Purified protein synthesis initiation factors IF-E2 and IF-E3 from rabbit reticulocytes were phosphorylated in vitro with protein kinases isolated from the same source. The highest levels of phosphorylation resulted from incubation of the factors with a cyclic nucleotide-independent protein kinase previously shown to have specificity for acidic proteins. The extent of phosphorylation of initiation factor IF-E2 was between 0.3 and 0.4 mol of phosphate per mol of factor complex, with either ATP or GTP as phosphoryl donor. Initiation factor IF-E2 is composed of three nonidentical polypeptides; only the polypeptide with a molecular weight of 52,000 was phosphorylated. The extent of phosphorylation of initiation factor IF-E3 was between 0.7 and 1.0 mol of phosphate per mol of factor complex with GTP as phosphoryl donor; with ATP, less phosphorylation of the factor was obtained. Initiation factor IF-E3 is composed of 9 to 11 nonidentical polypeptides; only 2 of these, with molecular weights of 120,000 and 70,000, were phosphorylated. A lower level of phosphorylation of initiation factor IF-E3 was found with the cyclic AMP-dependent protein kinase; the polypeptide of molecular weight 140,000 was the major site of phosphorylation.
Original languageEnglish
JournalJournal of Biological Chemistry
Volume251
Issue number20
Pages (from-to)6471-6474
Number of pages3
ISSN0021-9258
Publication statusPublished - 25. Oct 1976

Keywords

  • Adenosine Triphosphate
  • Animals
  • Electrophoresis, Polyacrylamide Gel
  • Guanosine Triphosphate
  • Molecular Weight
  • Peptide Initiation Factors
  • Protamine Kinase
  • Protein Kinases
  • Rabbits
  • Reticulocytes

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