Protein kinase C phosphorylates glutamyl-tRNA synthetase in rabbit reticulocytes stimulated by tumor promoting phorbol esters

R. C. Venema, J. A. Traugh

Research output: Contribution to journalArticle

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Abstract

A high M(r) synthetase core complex isolated from higher eukaryotes contains aminoacyl-tRNA synthetases specific for arginine, aspartic acid, glutamic acid, glutamine, isoleucine, leucine, lysine, methionine, and proline. Previously, five of the synthetases were shown to be phosphorylated in reticulocytes, and the glutaminyl- and aspartyl-tRNA synthetases were shown to be selectively phosphorylated in response to 8-bromo cAMP (Pendergast, A.M., Venema, R.C., and Traugh, J.A. (1987) J. Biol. Chem. 262, 5939-5942). Exposure of reticulocytes to phorbol 12-myristate 13-acetate stimulates the selective phosphorylation of one synthetase in the complex, glutamyl-tRNA synthetase. Only the glutamyl-tRNA synthetase is modified to a significant extent when the purified complex is phosphorylated in vitro by protein kinase C; up to 0.7 mol of phosphate is incorporated per mol of synthetase. Two-dimensional phosphopeptide mapping shows a single tryptic phosphopeptide, which is identical for the enzyme modified in vitro by protein kinase C or in phorbol 12-myristate 13-acetate-stimulated cells. Phosphorylation in vivo is reproducibly accompanied by a 38 ± 10% reduction in aminoacylation activity of partially purified glutamyl-tRNA synthetase assayed in vitro. Phosphorylation in vitro has no detectable effect on aminoacylation. This difference may be due to the absence of a required effector molecule which alters activity by interaction with the phosphorylated synthetase. Glutamyl-tRNA synthetase is one of a growing number of translational components, including initiation factors, which are coordinately modified by protein kinase C in response to phorbol 12-myristate 13-acetate.

Original languageEnglish (US)
Pages (from-to)5298-5302
Number of pages5
JournalJournal of Biological Chemistry
Volume266
Issue number8
StatePublished - Jul 11 1991

Fingerprint

Glutamate-tRNA Ligase
Reticulocytes
Phorbol Esters
Ligases
Protein Kinase C
Tumors
Phosphorylation
Rabbits
Aminoacylation
Phosphopeptides
Acetates
glutaminyl-tRNA synthetase
Neoplasms
Aspartate-tRNA Ligase
8-Bromo Cyclic Adenosine Monophosphate
Amino Acyl-tRNA Synthetases
Peptide Initiation Factors
Isoleucine
Eukaryota
Glutamine

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Protein kinase C phosphorylates glutamyl-tRNA synthetase in rabbit reticulocytes stimulated by tumor promoting phorbol esters. / Venema, R. C.; Traugh, J. A.

In: Journal of Biological Chemistry, Vol. 266, No. 8, 11.07.1991, p. 5298-5302.

Research output: Contribution to journalArticle

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abstract = "A high M(r) synthetase core complex isolated from higher eukaryotes contains aminoacyl-tRNA synthetases specific for arginine, aspartic acid, glutamic acid, glutamine, isoleucine, leucine, lysine, methionine, and proline. Previously, five of the synthetases were shown to be phosphorylated in reticulocytes, and the glutaminyl- and aspartyl-tRNA synthetases were shown to be selectively phosphorylated in response to 8-bromo cAMP (Pendergast, A.M., Venema, R.C., and Traugh, J.A. (1987) J. Biol. Chem. 262, 5939-5942). Exposure of reticulocytes to phorbol 12-myristate 13-acetate stimulates the selective phosphorylation of one synthetase in the complex, glutamyl-tRNA synthetase. Only the glutamyl-tRNA synthetase is modified to a significant extent when the purified complex is phosphorylated in vitro by protein kinase C; up to 0.7 mol of phosphate is incorporated per mol of synthetase. Two-dimensional phosphopeptide mapping shows a single tryptic phosphopeptide, which is identical for the enzyme modified in vitro by protein kinase C or in phorbol 12-myristate 13-acetate-stimulated cells. Phosphorylation in vivo is reproducibly accompanied by a 38 ± 10{\%} reduction in aminoacylation activity of partially purified glutamyl-tRNA synthetase assayed in vitro. Phosphorylation in vitro has no detectable effect on aminoacylation. This difference may be due to the absence of a required effector molecule which alters activity by interaction with the phosphorylated synthetase. Glutamyl-tRNA synthetase is one of a growing number of translational components, including initiation factors, which are coordinately modified by protein kinase C in response to phorbol 12-myristate 13-acetate.",
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