Translational inhibition by eIF-2-phospholipid complex in mammalian cell-free systems |
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Authors: | F Pelaez C de Haro |
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Institution: | Centro de Biologia Molecular, Consejo Superior de Investigaciones Cientificas, Madrid, Spain. |
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Abstract: | The polypeptide chain initiation factor 2 (eIF-2) binds phospholipid (PL) and becomes a potent inhibitor of translation in hemin-supplemented reticulocyte lysates De Haro et al. (1986) Proc. Natl. Acad. Sci. USA 83, 6711–6715]. This binding is independent of calcium ions and seems to be specific for phosphatidylinositol or phosphatidylserine; phosphatidic and arachidonic acids are inactive. Like -subunit-phosphorylated eIF-2, eIF-2·PL traps GEF in a non-dissociable eIF-2·PL·GEF complex whereby GEF is no longer able to recycle. Initiation is inhibited when no free GEF is available. Translational inhibition by eIF-2·PL is rescued by equimolar amounts of eIF-2·GEF. On the basis of this stoichiometry, we have estimated that reticulocyte lysates contain about 60 pmol of GEF/ml (60 nM) eIF-2·PL also inhibits translation in cell-free mouse liver extracts and this inhibition is prevented by reticulocyte eIF-2·GEF suggesting that GEF also functions in liver. However, the eIF-2·PL complex does not affect translation in such non-mammalian eukaryotic systems as wheat germ and Drosophila embryos. |
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Keywords: | Protein synthesis Guanosine exchange factor trapping of Phospholipid effect Translation inhibition (Eukaryote) |
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