Comparison of amino acid incorporation into nuclear protein of rat liver and thymus in cell free systems.

Abstract

1. Amino acid incorporation into proteins of rat liver and thymus nuclei were compared using cell free systems. 2. Both thymus and liver nuclei incorporated amino acids into their proteins without addition of high-energy phosphates. Amino acid incorporation into thymus nuclear proteins was not modified by ATP, CTP, GTP, and UTP added to the incubation medium, whereas amino acid incorporation into liver nuclear proteins was stimulated by ATP and GTP. In the presence of phosphoenolpyruvate and pyruvate kinase [EC 2.7.1.40] in the incubation medium, oligomycin, an inhibitor of oxidative phosphorylation, inhibited amino acid incorporation into thymus nuclear proteins.and this inhibition was not restored by ATP added. Under the same conditions oligomycin did, however, not inhibit amino acid incorporation into liver nuclear proteins. 3. Potassium and sodium ions inhibited amino acid incorporation into rat thymus nuclear proteins under the conditions of this study, but these ions stimulated amino acid incorporation into liver nuclear proteins. 4. RNase [EC 2.7.7.16] inhibited amino acid incorporation into liver nuclear proteins, but it did not affect amino acid incorporation into thymus nuclear proteins. DNase [EC 3.1.4.5] did not affect amino acid incorporation into both liver and thymus nuclear proteins.