Identification of protein phosphatases 1 and 2B as ribosomal protein S6 phosphatases in vitro and in vivo.
Protein phosphatases 1 and 2B from rabbit skeletal muscle were found to catalyze the dephosphorylation of ribosomal protein S6 in vitro. Phosphorylation of protein phosphatase-1 by the transforming protein of Rous sarcoma virus, pp60v-src, abolished S6 dephosphorylation by the purified enzyme. Analysis of the dephosphorylation of phosphorylase a and phosphorylase kinase in Xenopus oocyte extracts and after microinjection indicated the presence of oocyte enzymes similar to protein phosphatases-1 and -2B. Studies with 32P-labeled 40 S ribosomal subunits suggested that these enzymes were functioning as S6 phosphatases in oocytes. These findings support the hypothesis that regulation of protein phosphatase activity may be involved in the increase in S6 phosphorylation observed after mitogenic stimulation.
Andres
J L
JL
Department of Pharmacology, University of Colorado School of Medicine, Denver 80262.
Johansen
J W
JW
Maller
J L
JL
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D009132:Muscles / Q000201:enzymology; D015688:Oncogene Protein pp60(v-src); D009865:Oocytes / Q000201:enzymology; D010749:Phosphoprotein Phosphatases / Q000302:isolation & purification / Q000494:pharmacology*; D010766:Phosphorylation; D054645:Protein Phosphatase 1; D011817:Rabbits; D012191:Retroviridae Proteins / Q000494:pharmacology; D038601:Ribosomal Protein S6; D012269:Ribosomal Proteins / Q000378:metabolism*
D012191:Retroviridae Proteins; D038601:Ribosomal Protein S6; D012269:Ribosomal Proteins; D004533:Egtazic Acid; D015688:Oncogene Protein pp60(v-src); D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D002118:Calcium