Abstract
RABBIT reticulocytes, after incubation in a nutritional medium with radioactive inorganic phosphate, contain a significant amount of covalently bound phosphate. Approximately 65% of this phosphate is attached to ribosome-associated proteins which are released into the 0.5 M KCl wash fraction from ribosomes; the remainder is bound to ribosomal protein1. The high salt wash fraction contains various proteins required for the initiation and maintenance of protein synthesis. To analyse the effects of phosphorylation on the regulation of protein synthesis, purified initiation factors from rabbit reticulocytes have been examined for phosphate-acceptor activity through the use of cyclic AMP-regulated and cyclic nucleotide-independent protein kinases. Here we describe the phosphorylation of two factors previously shown to be involved in the initiation of haemoglobin synthesis. Both IF-MP, the Met-tRNAf binding factor, and IF-M2A, a ribosome-dependent GTPase activity, are modified by a cyclic nucleotide-independent protein kinase isolated from rabbit reticulocytes. Initiation factors IF-M1 (ref. 2), IF-M2Bα (ref. 3), IF-M2Bβ (ref. 3), IF-M3 (ref. 4) and IF-M4 (ref. 5) are not phosphorylated by this enzyme.
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TRAUGH, J., TAHARA, S., SHARP, S. et al. Factors involved in initiation of haemoglobin synthesis can be phosphorylated in vitro. Nature 263, 163–165 (1976). https://doi.org/10.1038/263163a0
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DOI: https://doi.org/10.1038/263163a0
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