Effects of cholera toxin and actinomycin on synthesis of [35S]methionine-labeled proteins during progesterone-induced maturation of Xenopus laevis oocytes

The incorporation of ³⁵S]methionine into polypeptides during progesterone-induced meiotic maturation of Xenopus laevis oocytes was studied by two-dimensional polyacrylamide gel electrophoresis. Five modifications were consistently observed: two polypeptides of an approximate molecular weight of 150K daltons and pI 5 were new proteins, two represent increased incorporation and one was decreased incorporation. Cholera toxin inhibited the appearance of the modifications induced by progesterone. Actinomycin and enucleation did not significantly alter the modifications. These data indicate that a good correlation exists between the modifications in protein synthesis induced by progesterone and the resumption of meiotic cell division.