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XB-ART-29332
Proc Natl Acad Sci U S A 1985 Feb 01;823:742-6.
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A protein kinase from Xenopus eggs specific for ribosomal protein S6.

Erikson E , Maller JL .


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A protein kinase specific for ribosomal protein S6 has been purified from eggs of Xenopus laevis. As visualized on a silver-stained polyacrylamide gel, the major protein in the preparation migrated with a Mr of 90,000. Incubation of the enzyme preparation with [gamma-32P]ATP led to phosphorylation of this protein on serine residues. Upon glycerol gradient centrifugation, the S6 kinase activity and the Mr 90,000 protein both sedimented with a Mr of 50,000-55,000. Two-dimensional gel electrophoresis demonstrated that up to 4-5 phosphate groups per S6 molecule could be incorporated with this enzyme in vitro, and two-dimensional peptide mapping demonstrated that the phosphopeptides from S6 labeled in vitro with the enzyme comigrated with those from highly phosphorylated S6 labeled in vivo in response to progesterone treatment. The purified S6 protein kinase did not phosphorylate at a significant rate ribosomal protein S10, histone H1, histone H4, mixed histones, casein, or phosvitin, indicating a high degree of substrate specificity. These results indicate that activation of a single S6 protein kinase may be sufficient to account for increased S6 phosphorylation after a growth stimulus.

???displayArticle.pubmedLink??? 3856226
???displayArticle.pmcLink??? PMC397122
???displayArticle.link??? Proc Natl Acad Sci U S A
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Species referenced: Xenopus laevis
Genes referenced: h4c4 psmd6 rps6ka3 vtga2

References [+] :
Beavo, Preparation of homogeneous cyclic AMP-dependent protein kinase(s) and its subunits from rabbit skeletal muscle. 1974, Pubmed