Changes in sedimentation properties of ribosomal ribonucleic acids during the course of ribosome formation in Escherichia coli

The nascent ribosomal RNA which has not yet been incorporated into mature ribosomal particles has been reported to sediment as 17 S and 22–23 S as compared with 16 S and 23 S for RNA from mature ribosomes. In this study, we have investigated whether the transformation of sedimentation property from nascent to mature state takes place gradually during ribosome formation or occurs at the later step of ribosome maturation.

Ribosomal RNA's were labelled either with [³H]adenosine or [¹⁴C]adenine at different stages of ribosome maturation, representing pulse-labelled RNA, RNA obtained in the presence of chloramphenicol or 5-fluorouracil, and RNA of mature ribosomes. Comparison of their sedimentation velocities in sucrose density gradient indicated that transformation from 17 S to 16 S occurs at the later step of ribosome maturation. No clear difference of sedimentation velocity was detected between nascent and mature 23-S ribosomal RNA in this study.