Characterization of ribosomal particles and ribonucleic acids of proliferating and starving cells of yeast

Abstract

1. 1. Ribosomes obtained from proliferating yeast cells and from nitrogen-starved cells manifested similar sedimentation patterns with one peak of 80 S. 2. 2. The velocity of amino acid uptake observed in nitrogen-starved cells was remarkably smaller than that in proliferating cells. Similarly, the cell-free system obtained from the nitrogen-starved cell had no amino-acid-incorporating activity, while that from the proliferating cells was remarkably active. The failure of incorporation of the starved system was found to be due to degradation of a ribosomal component. 3. 3. Ribosomal RNA extracted from proliferating cells gave two peaks of 19 S and 28 S in the sedimentation diagrams, but the ribosomal RNA from nitrogen-starved cells exhibited degraded components in addition to the integral components. This suggests that some essential ribosomal component, such as template RNA, is degraded in the nitrogen-starved ribosome. 4. 4. The above suggestion is supported by the finding that the incorporation capacity of the starved ribosome increased remarkably by the addition of intact ribosomal RNA.