Figure 3.

Gel analysis of epitope-tagged ZP glycoproteins synthesized and secreted by growing mouse oocytes. Two hundred growing oocytes were isolated from 13-d-old mice, microinjected with Myc-mZP2, and cultured in M199-M for ∼5 h. Oocytes were then transferred to Met/Cys-depleted M199-M, supplemented with 4 mCi/ml [³⁵S]Met/Cys. The culture medium was collected after ∼15 h and immunoprecipitated with monoclonal antibodies directed against Myc (9E10). Immunoprecipitates were subjected to 7.5% SDS-PAGE, as described in MATERIALS AND METHODS. Media from uninjected and injected oocytes probed with anti-Myc are shown in A and B, respectively. An arrowhead indicates the position of mZP2. Media were immunoprecipitated once again with an anti-mZP2 polyclonal antibody. As shown in C and D, both injected and noninjected oocytes secreted endogenous mZP2 glycoproteins. A band at ∼70 kDa was observed as a contaminant in all lanes. The positions of molecular mass standards are shown.