DECODING FIDELITY AT THE RIBOSOMAL-A AND RIBOSOMAL-P SITES - INFLUENCE OF MUTATIONS IN 3 DIFFERENT REGIONS OF THE DECODING DOMAIN IN 16S RIBOSOMAL-RNA

The involvement of defined regions of Escherichia coli 16S rRNA in the fidelity of decoding has been examined by analyzing the effects of rR NA mutations on misreading errors at the ribosomal A and P sites. Muta tions in the 1400-1500 region, the 530 loop and in the 1050/1200 regio n (helix 34) all caused readthrough of stop codons and frameshifting d uring elongation and stimulated initiation from non-AUG codons at the initiation of protein synthesis. These results indicate the involvemen t of all three regions of 16S rRNA in decoding functions at both the A and P sites. The functional similarity of all three mutant classes ar e consistent with close physical proximity of the 1400-1500 region, th e 530 loop and helix 34 and suggest that all three regions of rRNA com prise a decoding domain in the ribosome.