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Biochem J. 1993 Jul 1;293 ( Pt 1):31-4.

Cyclic AMP-dependent protein kinase phosphorylates rabbit reticulocyte elongation factor-2 kinase and induces calcium-independent activity.

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  • 1Department of Biochemistry, School of Medical Sciences, University of Bristol, U.K.

Abstract

The catalytic subunit of cyclic AMP-dependent protein kinase (PKA) phosphorylated purified calcium/calmodulin-dependent eukaryotic elongation factor-2 (eEF-2) kinase, isolated from rabbit reticulocyte lysates. It maximally incorporated about 1 mol of phosphate/mol of eEF-2 kinase. The Km of eEF-2 kinase for PKA was calculated to be 7 microM. Phosphorylation of eEF-2 kinase by PKA induced calcium-independent activity which amounted to 40-50% of the total activity measured in the presence of calcium. Furthermore, the level of calcium-independent activity induced by phosphorylation by PKA was similar to that induced by the calcium-stimulated autophosphorylation of eEF-2 kinase. Phosphopeptide mapping of eEF-2 kinase labelled by autophosphorylation and by PKA revealed a number of common phosphopeptides. This suggests that PKA may phosphorylate the same site(s) which are phosphorylated autocatalytically and which are responsible for the induction of calcium-independent activity. The possible implications these findings have for the control of translation are discussed.

PMID:
8328970
[PubMed - indexed for MEDLINE]
PMCID:
PMC1134316
Free PMC Article
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