Fig. 4

Fig. 4 Fertilization induces transient activation of Src-family PTKs. The effect of fertilization on Src-family PTK activity was measured using a single cell assay (left panel). Individual zebrafish eggs were collected before and at different times after fertilization, transferred to a micro pipet tip then crushed at the time (minutes) indicated at the top of the Figure and the PTK activity in each egg was assayed as described in materials and methods. The resultant ³²PO₄-labeled proteins were analyzed by SDS-PAGE and subjected to partial alkaline hydrolysis to reduce contamination by ³²PO₄-Ser and ³²PO₄-Thr. The remaining phosphoproteins were detected by autoradiography. The position of the 60-kDa band indicative of Src-family PTK activity is indicated by the arrow. The effect of the PTK inhibitor PP2 on this type of assay was examined in a second experiment (right panel). Eggs collected at 5 min postinsemination were assayed in the presence of different concentrations of the PTK inhibitor PP2 or the inactive analog PP3. The concentration of each inhibitor (nanomolar) is indicated at the top.