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  • 标题:Recycling and phosphorylation of eukaryotic initiation factor 2 on 60S subunits of 80S initiation complexes and polysomes
  • 本地全文:下载
  • 作者:K V Ramaiah ; R S Dhindsa ; J J Chen
  • 期刊名称:Proceedings of the National Academy of Sciences
  • 印刷版ISSN:0027-8424
  • 电子版ISSN:1091-6490
  • 出版年度:1992
  • 卷号:89
  • 期号:24
  • 页码:12063-12067
  • DOI:10.1073/pnas.89.24.12063
  • 语种:English
  • 出版社:The National Academy of Sciences of the United States of America
  • 摘要:Phosphorylation of the alpha-subunit (38 kDa) of eukaryotic initiation factor 2 (eIF-2 alpha) regulates initiation of protein synthesis in eukaryotic cells. This phosphorylation is enhanced in cycloheximide-treated heme-deficient reticulocyte lysates in which polysomes are maintained. In early heme deficiency prior to polysome disaggregation, eIF-2(alpha P) accumulates primarily on the 60S subunits of polysomes. Further, isolated polysomes contain eIF-2 alpha that is efficiently phosphorylated in vitro by heme-regulated inhibitor (HRI). Immunoblot analysis of eIF-2 distribution in sucrose gradients of actively protein-synthesizing lysates indicates that eIF-2 is distributed at low levels throughout the polysome profiles. These findings suggest that polysome-bound eIF-2 alpha is a target of HRI under physiological conditions. The presence of eIF-2 on the 60S subunits of polysomes is incompatible with the conventional model in which eIF-2 is recycled during the joining of the 48S preinitiation complex and the 60S subunit to form the 80S initiation complex. A modified model is presented with emphasis on the translocation of eIF-2 from the 40S ribosomal subunit of the 48S preinitiation complex (eIF-2.GTP.Met-tRNA(f).40S.mRNA) to the 60S subunit of the 80S initiation complex.
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