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We have studied the posttranslational modifications of the 52-kD protein, an estrogen-regulated autocrine mitogen secreted by several human breast cancer cells in culture (Westley, B., and H. Rochefort, 1980, Cell, 20:353-362). The secreted 52-kD protein was found to be phosphorylated mostly (94%) on high-mannose N-linked oligosaccharide chains, and(More)
Specific inhibition of types 1 and 2A protein phosphatases by microinjection of okadaic acid (OA) into starfish oocytes induced germinal vesicle breakdown and activation of M phase-promoting factor (MPF) and histone H1 kinase. The effects were evident in immature oocytes arrested at first meiotic prophase as well as in fully mature oocytes arrested at the(More)
Activation of the phosphoinositide transduction pathway induces capacitative Ca2+ entry in Xenopus oocytes. This can also be evoked by intracellular injection of Ins(1,4.5)P3, external application of thapsigargin and/or incubation in a Ca2+-free medium. Readmission of Ca2+ to voltage-clamped, thapsigargin-treated Xenopus oocytes triggers Ca2+-dependent Cl-(More)
In a previous paper (J. Steroid Biochem. 29 (1988) 475-480), the isolation of a 17 kDa protein that was dramatically induced in the uterus of estrogen-treated spayed rats was presented. We now describe a new purification procedure that is compatible with microsequencing of the 17 kDa protein. The protein partial N-terminal amino acid sequence analysis gave(More)
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(More)
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