The study of proteins during early stages of embryogenesis of sea urchins : I. Investigations on the distribution of preexisting and of de novo synthesized proteins.

The distribution of the preexisting and of thede novo synthesized proteins among soluble, and insoluble fractions, as well as between immunoprecipitable and non-immunoprecipitable soluble proteins has been studied in sea urchin embryos at different stages of development.In the S-100 fraction, which represented about 20% of total proteins, only a minor part of radioactivity was found. The majority of newly synthesized proteins was insoluble at neutral pH. Such distribution was practically invariant for all investigated stages of development, and was not markedly affected by Dactinomycin nor by 5-azacytidine.Only a small percentage of the total radioactivity of the S-100 fraction was found in the antigen-antibody complexes of soluble proteins. No "shift" of newly synthesized proteins towards the type of old, preexisting antigenic proteins was detected, and the majority of soluble newly synthesized proteins was found to be related to the non-immunoprecipitable soluble proteins.