Do ribosomal RNAs act merely as scaffold for ribosomal proteins?

Sites of ribosomal RNAs involved in the subunit association of tight and loose couple ribosomes

It was demonstrated previously by kethoxal treatment studies that tight (TC) and loose (LC) couple ribosomes use different sites of the 16 S and 23 S RNAs for subunit association (Burma, D. P., Srivastava, A. K., Srivastava, S., and Dash, D. (1985) J. Biol. Chem. 260, 10517-10525). To localize these sites, a number of oligodeoxynucleotides complementary to the suspected sites of the 16 S and 23 S RNAs were synthesized, and their binding to ribosomes and effects on subunit association were studied. Some of the probes inhibit the association of both TC and LC ribosomes, some inhibit the association of TC but not LC ribosomes, and some inhibit the association of LC but not TC ribosomes. It appears that both TC and LC ribosomes use one common site of association, bases 818-823 of the 16 S and 2308-2313 of the 23 S RNA. The second site, 788-793 of the 16 S RNA and 2753-2758 of the 23 S RNA for TC ribosomes, and 783-791 of the 16 S RNA and 2295-2303 of the 23 S RNA for LC ribosomes, is not shared. This suggests a spatial movement of the ribosomal subunits with respect to one another and lends further support to the model of translocation based on the interconversion of TC and LC ribosomes.

Prediction of the recognition sites on 16S and 23S rRNAs from E. coli for the formation of 16S-23S rRNA complex

Interactions between RNA molecules have been postulated to play an important role in the assembly of ribosomes. Using the sequence analysis and the search of continuous complementary regions on 16S rRNA and 23S rRNA, the recognition sites involved in the formation of ribosome of E. coli are postulated. The number of postulated sites was narrowed down by taking available experimental data. The suggestive evidence for correct postulation is obtained from sequence comparison studies of 16S and 23S rRNAs from various species. The sites 891-899 and 1195-1203 on 16S rRNA along with the corresponding complementary sites 1904-1912 and 760-768 on 23S rRNA are predicted to be the most probable candidates for the sites of recognition between 16S and 23S rRNAs. The possibility of the involvement of the additional site 630-638 on 16S rRNA with its complementary site 2031-2039 on 23S rRNA cannot be ruled out.