Reevaluation of cell surface protein release at fertilization and its role in regulation of sea urchin egg protein synthesis

Abstract

We have reexamined conditions for release of labeled cell surface proteins from sea urchin eggs and the effects of exogenous cell surface protein on the status of protein synthesis in activated eggs. As reported earlier ( J. D. Johnson and D. Epel, 1975, Proc. Nat. Acad. Sci. USA 72, 4474–4478 ), we find insemination and the Ca-ionophore A23187 induce release of labeled cell surface polypeptides but in contrast to that report we do not observe increased release during incubation in ammonia or nicotine. Electrophoretic analysis of the 125I-labeled polypeptides released after insemination indicates that the cell surface protein fraction contains a minimum of 10 polypeptides ranging from 22,000 to 200,000 daltons. In five experiments, the cell surface proteins released during the ammonia incubation had no significant effect on the status of protein synthesis in partially activated eggs.