DIFFERENTIAL PHOSPHORYLATION OF A 57-KDA PROTEIN-TYROSINE KINASE DURING EGG ACTIVATION

Fertilization results in activation of many protein kinases which func tion during egg activation. We have used metabolic labelling and immun oprecipitation to study changes in the phosphorylation state of a 57-K Da src-family protein tyrosine kinase during fertilization of the sea urchin egg. The kinase was phosphorylated on serine at all periods stu died but it was also phosphorylated transiently on tyrosine at 5 minut es post insemination and then on threonine at 90 minutes after fertili zation. These data indicate that the 57-KDa PTK may be under complex r egulatory control during the first cell cycle. (C) 1995 Academic Press , Inc.