The isolation of a specific species of ribosomes associated with chloroplast development in Euglena gracilis

Abstract

1. Ribosomal particles were isolated from the chloroplast fraction of Euglena gracilis. The RNA nucleotide composition of the purified particles is dras different from that of the ribosomes obtained from the microsome fraction of the cells. 2. The chloroplast ribosomes have a sedimentation value somewhat lower than that of the microsomal particles, and show the characteristic dissociation into subunits in the absence of Mg ions. 3. The cellular localization of the chloroplast particles was confirmed by comparing their nucleotide composition to that of the RNA of Euglena chloroplasts purified by flotation. 4. A small amount of the chloroplast ribosomes may be present in the cells grown in the dark (colorless cells). 5. The possible relation of these specific ribosomal particles to the synthesis of the chloroplast proteins is discussed.