Identification of a protein kinase activity in rabbit reticulocytes that phosphorylates the mRNA cap binding protein.

McMullin EL, Haas DW, Abramson RD, Thach RE, Merrick WC, Hagedorn CH
Biochem Biophys Res Commun. 1988 153 (1): 340-6

PMID: 2967701 · DOI:10.1016/s0006-291x(88)81228-2

The 25 kDa mRNA cap binding protein can be purified in a partially phosphorylated state and the extent of its phosphorylation appears to be regulated during heat shock and mitosis in mammalian cells. We demonstrated that a nonabundant serine protein kinase activity exists in rabbit reticulocytes that phosphorylates the 25 kDa cap binding protein in both the free (eIF-4E) and complexed (eIF-4F) state. This kinase was not inhibited by the cAMP-dependent protein kinase inhibitory peptide IAAGRTGRRNAIHDILVAA, did not phosphorylate S6 ribosomal protein, did not phosphorylate p220 of eIF-4F as protein kinase C does and no other substrates for this kinase were apparent in reticulocyte ribosomal salt wash. The molecular identity of this kinase, the specific site(s) of eIF-4E that it phosphorylates and its in vivo regulatory role remain to be studied.

MeSH Terms (13)

Animals Carrier Proteins Eukaryotic Initiation Factor-4E Eukaryotic Initiation Factor-4F Intracellular Signaling Peptides and Proteins Peptide Initiation Factors Phosphorylation Protein-Serine-Threonine Kinases Protein Kinases Rabbits Reticulocytes RNA Cap-Binding Proteins RNA Caps

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