Fig. 4. IAK1/Eg2 blocking peptide inhibits first polar body extrusion. Oocytes were injected with the peptides noted in Fig. 3B, except that in this case they were not coupled to ovalbumin. The rate of polar body extrusion during maturation was assessed. While the wild-type peptide only moderately inhibited polar body extrusion, the mutant, alanine-containing peptide was more effective in doing so. Although both peptides bind Eg2, the binding to the mutant peptide is essentially irreversible, and thus it is a more effective competitive inhibitor of kinase activity. In this analysis, 29 oocytes were assessed for the wild-type peptide, 18 oocytes for the mutant peptide and 47 oocytes that were not injected. The experiment was performed twice.