Differences in size and number of 80 S and 70 S ribosomal proteins by dodecyl sulfate gel electrophoresis.

ribosome contained twice as many proteins as the bacterial The molecular weight distributions of the ribosomal proribosome. This work was undertaken to compare quantitatively teins from Escherichia coli, Micrococcus lysodeikticus, &othe molecular weight distribution and number of ribosomal proplasmic ribosomes of Euglena and mouse plasmocytoma teins from representative procaryotes and eucaryotes. were compared by electrophoresis in acrylamide gels containing sodium dodecyl sulfate. The gels were quantitatively analyzed by spectrophotometric scanning of the protein bands stained with Coomassie brilliant blue. The weight average and number average molecular weights of the proteins of each ribosomal subunit were calculated. The average molecular weights obtained for the two kinds of bacteria were similar and were significantly smaller than those for the two kinds of eucaryotic proteins. The number of moles of protein per 80 S ribosome was estimated to be between 60 and 80, as compared with 40 to 60 proteins per 70 S ribosome. The increased protein content of eucaryotic ribosomes, as compared with bacterial, is explained both by the presence of a greater number of moles of protein and by proteins of larger average size.