Early increase of a 105,000-dalton phosphoprotein during meiotic maturation of Xenopus laevis oocyte.
In ovo [32P] phosphoproteins were analyzed during meiotic maturation of Xenopus laevis oocytes. A phosphoprotein of 105,000-dalton was found to increase early (one hour) after progesterone induction of meiosis. The pure heat-stable inhibitor (PKI) of cAMP-dependent protein kinase, which induces maturation, was microinjected into oocytes. Again the early increase in the 105,000-dalton [32P] phosphoprotein occurred. The burst in protein phosphorylation, which takes place at the period of germinal vesicle breakdown, was quantitatively and qualitatively comparable in progesterone and PKI-stimulated oocytes. In order to confirm the inverse relationship between the 105,000 dalton [32P] phosphoprotein increase and cAMP-dependent protein kinase activity, purified C-subunit of the kinase has been microinjected into oocytes. C-subunit which inhibits maturation did not increase significantly the 105,000-dalton [32P] phosphoprotein whereas it increased the total level of in ovo phosphorylation. Enucleation experiments favour the localization of the 105,000-dalton protein in both the oocyte cytoplasm and nucleus. Furthermore the progesterone-induced increase in the phosphorylation of the 105,000-dalton protein was found in the cytoplasmic compartment after oocyte enucleation.
D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D008540:Meiosis; D008845:Microinjections; D008970:Molecular Weight; D009865:Oocytes / Q000032:analysis* / Q000254:growth & development*; D010063:Ovum / Q000032:analysis* / Q000254:growth & development*; D010750:Phosphoproteins / Q000032:analysis*; D011247:Pregnancy; D011374:Progesterone / Q000494:pharmacology; D047428:Protein Kinase Inhibitors; D014982:Xenopus laevis
D010750:Phosphoproteins; D047428:Protein Kinase Inhibitors; D011374:Progesterone; D000242:Cyclic AMP