Identification of novel phosphorylation sites in the beta-subunit of translation initiation factor eIF-2

Biochem Biophys Res Commun. 1994 Jun 30;201(3):1279-88. doi: 10.1006/bbrc.1994.1843.

Abstract

Initiation factor eIF-2 (a trimer of subunits alpha, beta and gamma) attaches the initiator Met-tRNA to the ribosome during the initiation of translation in eukaryotic cells. Both the alpha and beta subunits can be phosphorylated although the sites in the beta-subunit have not previously been fully identified. Here we identify the sites at which eIF-2 beta is phosphorylated in vitro by three well-characterised protein kinases, casein kinase-2 (which phosphorylates serine residues-2 and -67), protein kinase C (serine-13) and cAMP-dependent protein kinase (serine-218). This constitutes an essential prerequisite for studying the phosphorylation of eIF-2 beta in vivo. Indeed, we present evidence that at least one of these sites (serine-67) is phosphorylated in reticulocytes. The major kinase activity against eIF-2 beta in reticulocyte lysates appears in CK-2 and protein phosphatase-2A is the principal enzyme responsible for dephosphorylation of eIF-2 beta phosphorylated by this kinase.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Creatine Kinase / metabolism
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Eukaryotic Initiation Factor-2 / metabolism*
  • Molecular Sequence Data
  • Peptide Fragments / chemistry
  • Peptide Mapping
  • Phosphorylation
  • Phosphoserine / metabolism
  • Phosphothreonine / metabolism
  • Protein Kinase C / metabolism
  • Rabbits

Substances

  • Eukaryotic Initiation Factor-2
  • Peptide Fragments
  • Phosphothreonine
  • Phosphoserine
  • Cyclic AMP-Dependent Protein Kinases
  • Protein Kinase C
  • Creatine Kinase