The proteins of the cytoplasmic ribosomes of Euglena gracilis.

Two types of cytoplasmic ribosomes of Euglena gracilis have been found when the stability in vitro of the large subunit at 25 degrees C for 30 min has been considered. Sucrose density gradient analysis have revealed that the large subunit of ribosomes obtained from cells harvested in the stationary phase of growth was degraded when heated at 25 degrees C. The large subunit of ribosomes obtained from exponentially growing cells was stable in the same experimental conditions. Studies of the ribosomal RNAs have not explained this differential stability observed in vitro. In fact, after SDS-extraction, the largest RNA species always appears degraded in both types of ribosomes. Therefore, an explanation to this phenomenon have been searched for through the analysis of the ribosomal proteins. One and two dimensional gel electrophoresis techniques have been employed. At least one difference between the two ribosomal protein groups has been observed and this could be associated to the differential stability of the ribosomes. Approximately 72 proteins molecules have been found in Euglena's cytoplasmic ribosome. About 42 proteins belong to the large subunit and 30 to the small one.