Phosphorylation of valyl-tRNA synthetase and elongation factor 1 in response to phorbol esters is associated with stimulation of both activities.
Valyl-tRNA synthetase from mammalian cells is isolated in a high Mr complex with elongation factor 1 (EF-1). This complex, which represents all of the valyl-tRNA synthetase activity and a significant portion of the EF-1 activity in rabbit reticulocytes, contains five polypeptides identified as valyl-tRNA synthetase and the four subunits of EF-1. In this study, we have examined the potential for regulation of the complex by phosphorylation of these components. The valyl-tRNA synthetase.EF-1 complex has been purified by gel filtration and tRNA-Sepharose chromatography from 32P-labeled rabbit reticulocytes stimulated by phorbol 12-myristate 13-acetate (PMA) and compared to the complex purified from control cells. One- and two-dimensional polyacrylamide gel electrophoresis and autoradiography show that valyl-tRNA synthetase and the alpha, beta and delta subunits of EF-1 are phosphorylated in vivo. Phosphorylation of each of the four proteins is increased 2-4-fold in response to PMA. Phosphorylation of valyl-tRNA synthetase in response to PMA is reproducibly accompanied by a 1.7-fold increase in aminoacylation activity, whereas phosphorylation of EF-1 is associated with a 2.0-2.2-fold stimulation of activity, as measured by poly(U)-directed polyphenylalanine synthesis. These data suggest that stimulation of translational rates in response to PMA is mediated, at least in part, by phosphorylation of valyl-tRNA synthetase and EF-1.
Venema
R C
RC
Department of Biochemistry, University of California, Riverside 92521.
Peters
H I
HI
Traugh
J A
JA
D000818:Animals; D001345:Autoradiography; D002850:Chromatography, Gel; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors / Q000378:metabolism*; D010766:Phosphorylation; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014637:Valine-tRNA Ligase / Q000378:metabolism*
D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors; D014637:Valine-tRNA Ligase; D013755:Tetradecanoylphorbol Acetate