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  • Title: Allosteric activation of rabbit reticulocyte guanine nucleotide exchange factor activity by sugar phosphates and inositol phosphates.
    Author: Singh LP, Wahba AJ.
    Journal: Biochem Biophys Res Commun; 1995 Dec 14; 217(2):616-23. PubMed ID: 7503743.
    Abstract:
    Sugar phosphates are required to maintain active rates of translation in gel-filtered rabbit reticulocyte lysates. They may stimulate polypeptide chain initiation by acting as NADPH generators or by a direct interaction with initiation factor(s). We now provide evidence for the allosteric activation of the purified guanine nucleotide exchange factor (eIF-2B) by sugar phosphates and inositol phosphates. In the presence of microM fructose 1,6-bisphosphate, the rate of eIF-2B-catalyzed GDP/GTP exchange is increased approximately 2-fold. The half-maximal concentration for stimulation of eIF-2B activity (SC50) is 57 microM. The binding of GTP to isolated eIF-2B is stimulated 1.5-fold, whereas GTP-binding to ALP-treated eIF-2B is not affected by sugar phosphates. Inositol 1,4-bisphosphate, like fructose 1,6-bisphosphate, stimulates 2-3-fold the activity of the isolated eIF-2B (SC50, 140 microM).
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