Isolation of Ribosome Particles from Meningopneumonitis Organisms

Abstract

In ribonucleic acid (RNA) extracted by phenol and sodium dodecyl sulfate from purified reticulate bodies of meningopneumonitis (MP) organisms, 21 S , 16 S , and 4 S RNA were found by sucrose density gradient sedimentation analysis. When purified reticulate bodies were homogenized by sonic treatment or by treatment with sodium deoxycholate and were fractionated by differential centrifugation, more than 50% of the RNA was recovered in the fraction which was sedimented by centrifugation at 105,000 × g for 2 hr, but not at 13,000 × g for 20 min. From homogenates prepared in this manner, 50 S and 30 S particles containing RNA were isolated by sucrose density gradient centrifugation. These 50 S and 30 S particles were also found in lysates of cytoplasmic fractions of infected cells which were labeled by 32 P during 17 to 17.5 hr or 15 to 18 hr after infection. The synthesis of 50 S and 30 S particles was not inhibited by actinomycin D. When infected cells were homogenized in the presence of 0.01 or 0.02 m MgCl 2 , 70 S particles were isolated instead of 50 S and 30 S particles. When dialyzed against low concentrations of MgCl 2 , the 70 S particles dissociated to 50 S and 30 S particles. The base ratio of the 70 S particles is very similar to that of 16 S plus 21 S RNA. The characteristics of the 70 S , 50 S , and 30 S particles suggest that these are ribosome particles, similar to bacterial ribosomes.