Analysis of the ribosome large subunit assembly and 23 S rRNA stability in vivo.

The ability of mutant 23 S ribosomal RNA to form particles with proteins of the large ribosomal subunit in vivo was studied. A series of overlapping deletions covering the entire 23 S rRNA, were constructed in the plasmid copy of an E. coli 23 S rRNA gene. The mutant genes were expressed in vivo using an inducible tac promoter. Mutant species of 23 S rRNA, containing deletions between positions 40 and 2773, were incorporated into stable ribonucleoprotein particles. In contrast, if one end of the 23 S rRNA was deleted, the mutant rRNA was unstable and did not form ribosomal particles. Protein composition of the mutant particles was specific; the presence of the primary rRNA-binding proteins corresponded to their known binding sites. Furthermore, several previously unknown ribosomal protein binding sites in 23 S rRNA were identified. Implications of the results on ribosome assembly are discussed.