Fig. 1. Screening for potential PKA substrates from a mouse oocyte library. (A) Radiolabeled protein pools were generated and analyzed by a SDS-gel mobility shift assay. Asterisks indicate the proteins where mobility was shifted by incubation with PKA. (B) Radiolabeled proteins derived from isolated single clones (1-4B, 1-5B, 3-7F and 14-12D) were incubated with or without the PKA catalytic subunit, followed by a SDS-gel mobility shift assay. (C) mRNA from each independent clone were synthesized in vitro. Twenty nanograms of each mRNA (in 20 nl of H₂O) or 20 nl of H₂O (vehicle) were injected into 30 Xenopus oocytes 12 hours before 500 nM progesterone stimulation. Percentage of GVBD was measured by counting white spots on the animal pole of Xenopus oocytes.