Modification of ribosomal proteins in sea urchin eggs following fertilization

Analysis of the ribosomal proteins in sea urchin eggs by two-dimensional polyacrylamide gel electrophoresis revealed postfertilization changes in the proteins of both the small and the large subunits. Five egg-ribosomal proteins (S7, S16, S19, L19, L31) appeared to undergo rapid changes to the corresponding embryo-specific proteins. These changes were completed within 30 min after fertilization, and identical electrophoretic patterns were observed among the different developmental stages of embryos. One of the five proteins, S7, showed an increase in the phosphorylated form. The remainder showed qualitative shifts to the corresponding embryo-specific proteins; however, peptide map analyses revealed the existence of common structural units between the corresponding proteins. These modifications were observed in the three species of sea urchin studied (Pseudocentrotus depressus, Hemicentrotus pulcherrimus and Anthocidaris crassispina), except in the case of one protein (L31). Purification of ribosomes by different procedures based on high-salt treatment gave the same results with respect to the egg-specific and embryo-specific proteins.