Two distinct enzymes contribute to biphasic S6 phosphorylation in serum-stimulated chicken embryo fibroblasts.
Serum stimulation of quiescent chicken embryo fibroblasts resulted in a time-dependent, biphasic activation of S6 kinase activity. Chromatographic fractionation of serum-stimulated cell lysates resolved two distinct S6 kinase activities. Anti-Xenopus S6 kinase II antiserum immunoprecipitated a 90,000-Mr S6 kinase but did not cross-react with a smaller, 65,000-Mr S6 kinase. Phosphopeptide analysis confirmed that the 90,000- and 65,000-Mr proteins were structurally unrelated and established that the 65,000-Mr protein isolated by the current protocol was the same serum-stimulated chicken embryo fibroblast S6 kinase as that previously characterized (J. Blenis, C. J. Kuo, and R. L. Erikson, J. Biol. Chem. 262:14373-14376, 1987). These results demonstrate the contribution of two distinct S6 kinases to total serum-stimulated ribosomal protein S6 phosphorylation.
Sweet
L J
LJ
Department of Cellular and Developmental Biology, Harvard University, Cambridge, Massachusetts 02138.
Alcorta
D A
DA
Erikson
R L
RL
D000818:Animals; D001769:Blood; D002478:Cells, Cultured; D002642:Chick Embryo; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003470:Culture Media; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008970:Molecular Weight; D010449:Peptide Mapping; D010748:Phosphopeptides / Q000302:isolation & purification; D010766:Phosphorylation; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D019893:Ribosomal Protein S6 Kinases
D003470:Culture Media; D007527:Isoenzymes; D010748:Phosphopeptides; D011494:Protein Kinases; D019893:Ribosomal Protein S6 Kinases