Title: Stability of free ribosomes, derived ribosomes and polysomes of the sea urchin
Abstract: 1. The relative stabilities of free ribosomes and polysomes from various developmental stages of two species of sea urchin were examined on sucrose gradients in a wide range of ionic strengths. With increasing concentrations of KCl there is an increased tendency for free ribosomes to dissociate, and this response to KCl was used to assay any differences in subunit association during development. In moderate and high concentrations of KCl, the free ribosomes from unfertilized eggs dissociate into subunits as readily as free ribosomes from developing embryos. 2. The identical dissociation characteristics of free ribosomes from egg and embryo preparations is also observed during dialysis against Mg2+-free buffer, when care is taken in purifying the ribosomes prior to dialysis. Taken together, these results eliminate the possibility, as proposed by others, of a very tight association of ribosomal subunits in the egg which is reduced after fertilization. 3. In contrast to free ribosomes, the ribosomes derived from polysomes through brief nuclease digestion are extremely resistant to dissociation even in high KCl. They can be made susceptible to both moderate and high concentrations of salt by prior treatment with puromycin which causes release of the nascent polypeptides. 4. Both the extraction and integrity of polysomes are impervious to KCl concentrations from 0.05 to 0.6 M when ribonuclease activity in the embryo extract is inhibited. These results are discussed in terms of the methods used in the preparation of sea urchin polysomes and the variations in the sedimentation patterns of polysomes during early embryogenesis.
Publication Year: 1971
Publication Date: 1971-08-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 32
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