Katabolism of plant cytoplasmic ribosomes: A study of the interaction between ribosomes and ribonuclease.

Ribosome preparations from several species of flowering plant were found to contain ribonuclease. It was predominantly latent in ionic conditions which maintained the integrity of the ribosomes but was activated by agents which disrupted ribosome structure by chelating their divalent cations. The ribonuclease was not a structural component of the ribosomes but was preferentially adsorbed by them upon disruption of cells. Adsorption took place onto both large and small ribosomal subunits, and onto monosomes and polysomes. These results are discussed in relation to possible mechanisms for the breakdown of ribosomal RNA in vivo.