Changes in the polysomal pattern after fertilization in Fucus eggs.

At high potassium concentrations it is possible to isolate largely intact polysomes from fertilized and unfertilized Fucus vesiculosus eggs, and to study the distribution pattern of ribosomal particles in a sucrose gradient. The changes in the ribosomal pattern before and after fertilization reflect the time course of protein synthesis. In the unfertilized egg there is a pool of inactive light polysomes which are fairly resistant to ribonuclease treatment, whilst a heavier polysomal fraction shows some amino-acid incorporation activity. 2 hr after fertilization, the heavy polysome fraction is strongly increased and highly active; the light polysomes disappear. 6 hr after fertilization, when protein synthesis is depressed, new monomeric and possibly dimeric ribosomes are formed; these ribosomes have a very low incorporation activity. The rearrangement of ribosomal particles does not appear to be necessarily linked with the synthesis of new RNA.