title: Evidence for the exchangeability of acidic ribosomal proteins on cytoplasmic ribosomes in regenerating rat liver.
abstract: We purified acidic ribosomal proteins (P1 and P2) in good yield from rat liver ribosomes by precipitation of ribosomes with MgCl2 prior to ethanol extraction and chromatography of the extract on a column of CM-cellulose at pH 4.8. The newly-synthesized acidic ribosomal proteins in regenerating rat liver, labeled in vivo with [3H]leucine, were rapidly incorporated into cytoplasmic ribosomes without any detectable time lag and, after reaching a maximum at 30 min, they gradually disappeared from the ribosomes, suggesting a short metabolic-life. However, it was found later that they were re-incorporated slowly when newly-labeled proteins were "chased" by an injection of a large amount of cold leucine intraperitoneally at 15 min after the injection of [3H]leucine. Furthermore, in a long-term experiment, acidic ribosomal proteins were found to disappear with a half-life of 100 h from the ribosomes. Thus, these results suggest that acidic ribosomal proteins have a long metabolic life and are exchangeable on cytoplasmic ribosomes in regenerating rat liver.
mesh_terms: D000818:Animals; D003593:Cytoplasm / Q000032:analysis; D005260:Female; D006207:Half-Life; D007700:Kinetics; D008115:Liver Regeneration; D010750:Phosphoproteins / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012269:Ribosomal Proteins; D012270:Ribosomes / Q000378:metabolism*
chemical_list: D010750:Phosphoproteins; D012269:Ribosomal Proteins; C031937:phosphoprotein P2, ribosomal; C035690:ribosomal phosphoprotein P1