The effect of chick-liver ribonucleic acid on amino acid-incorporation systems from rat liver.

1. Rat-liver microsomes, ribonucleoprotein particles and a fraction mainly consisting of microsomal membranes were tested for their ability to incorporate amino acids into protein in the presence of ATP, GTP, phosphoenolpyruvate and pyruvate kinase. Addition of polyuridylic acid or of ribonucleic acid from rat-liver nuclei stimulated the incorporating activities. 2. These protein-synthesizing systems were found to be susceptible to ribonucleic acid from chick-liver nuclei as well. The biological activity of the ribonucleic acid from chick liver was measured by its capacity to stimulate amino acid incorporation. 3. In the presence of chick-liver ribonucleic acid, the ribonucleoprotein particles from rat liver showed an increased radioactivity in ribosomal units with a sedimentation constant higher than 70s. 4. This was investigated by sucrose-gradient centrifugation or by column chromatography on agarose suspensions.