Effect of phosphorylation of the alpha-subunit of eukaryotic initiation factor 2 on the function of reversing factor in the initiation of protein synthesis.
- 1 May 1983
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences
- Vol. 80 (9) , 2559-2563
- https://doi.org/10.1073/pnas.80.9.2559
Abstract
The reticulocyte reversing factor (RF) isolated as a complex with eukaryotic initiation factor 2 (eIF-2) acts catalytically in restoring protein synthesis in [rabbit] reticulocyte lysates inhibited by heme deficiency. In reconstituted in vitro assay mixtures containing Mg2+ (0.25-0.5 mM), RF catalyzes the formation of the binary complex (eIF-2.cntdot.GDP) but this effect is inhibited when eIF-2 is phosphorylated by the heme-regulated kinase for the .alpha.-subunit of eIF-2 (HRI). More significantly, RF catalyzes the rapid dissociation of (eIF-2.cntdot.GDP), which permits the exchange of GTP for GDP and, in the presence of Met-tRNAf, promotes the formation of the ternary complex (eIF-2.cntdot.Met-tRNAf.cntdot.GTP). Phosphorylation of the binary complex by HRI prevents its dissociation by RF and, as a consequence, ternary complex formation is inhibited. Phosphorylated binary complex [eIF-2(.alpha.P).cntdot.GDP] probably interacts with RF to form a [RF.cntdot.eIF-2(.alpha.P)] that is not readily dissociable. This binding of RF renders it unavailable to catalyze the dissociation of unphosphorylated binary complex, thereby blocking the recycling of eIF-2. Since RF is present in lysates at a limited concentration relative to that of eIF-2, the sequestering of RF in this manner could account for the observation that the phosphorylation of a small proportion of eIF-2 in heme-deficient lysates is sufficient to inhibit protein synthesis.This publication has 24 references indexed in Scilit:
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