Maturation-promoting factor causes germinal vesicle breakdown when injected into Xenopus oocytes and can induce metaphase in a cell-free system. The cell-free assay was used to monitor maturation-promoting factor during its purification from unfertilized Xenopus eggs. Ammonium sulfate precipitation and six chromatographic procedures resulted in a preparation purified greater than 3000-fold that could induce germinal vesicle breakdown within 2 hr when injected into cycloheximide-treated oocytes. Proteins of 45 kDa and 32 kDa were correlated with fractions of highest activity in both assays. These fractions contained a protein kinase activity able to phosphorylate the endogenous 45-kDa protein, as well as histone H1, phosphatase inhibitor 1, and casein. The highly purified preparations described here should help to identify the mechanism of action of maturation-promoting factor and to elucidate the role of protein kinases in the induction of metaphase.
[1]
R. A. Johnson,et al.
The enzymatic preparation of [alpha-32P]ATP, [alpha-32P]GTP, [32P]cAMP, and [32P]cGMP, and their use in the assay of adenylate and guanylate cyclases and cyclic nucleotide phosphodiesterases.
,
1979,
Advances in cyclic nucleotide research.
[2]
J. Maller,et al.
Metaphase protein phosphorylation in Xenopus laevis eggs
,
1987,
Molecular and cellular biology.