Mode of Degradation of Ribosomes in Regeneration Rat Liver in vivo.

The degradations of structural proteins and RNAs of ribosomes in regenerating rat liver were investigated with the following results. 1. Using a modification of the double isotope technique of Arias et al. (1969), it was found that almost all the structural proteins of both large and small ribosomal subunits, separated by dodecylsulfate or two-dimensional polyacrylamide gel electrophoresis, were apparently degraded at the same rates. 2. Studies on the changes in the specific activities of the RNA and protein moieties of the two ribosomal subunits after administration of [Me-³H]methionine as a common precursor showed that their specific activities decreased in parallel, with the same apparent half-life of about 4.5 days. 3. These results suggest that structural components of rat liver ribosomal subunits are degraded as a unit.