The Chloroplast and Cytoplasmic Ribosomes of Euglena: II. Characterization of Ribosomal Proteins.

Cytoplasmic and chloroplast ribosomal proteins were isolated from Euglena gracilis and analyzed on polyacrylamide gels. Cytoplasmic ribosomes appear to contain 75 to 100 proteins ranging in molecular weight from 10,200 to 104,000, while chloroplast ribosomes appear to contain 35 to 42 proteins with molecular weights ranging from 9,700 to 57,900. This indicates that the cytoplasmic ribosomes are similar in composition to other eucaryotic ribosomes, while chloroplast ribosomes have a protein composition similar to the 70S procaryotic ribosome. The kinetics of light-induced labeling of cytoplasmic ribosomal proteins during chloroplast development has been determined, and the results are compared with the kinetics of ribosomal RNA synthesis.