Recognition of the codon-anticodon helix by ribosomal RNA

Translational fidelity is established by ribosomal recognition of the codon -anticodon interaction within the aminoacyl-transfer RNA (tRNA) site (A sit e) of the ribosome. Experiments are presented that reveal possible contacts between 16S ribosomal RNA and the codon-anticodon complex. Nf methylation of adenine at position 1492 (A1492) and A1493 interfered with A-site tRNA b inding. Mutation of A1492 and A1493 to guanine or cytosine also impaired A- site tRNA binding. The deleterious effects of A1492G or A1493G (or both) mu tations were compensated by 2' fluorine substitutions in the mRNA codon. Th e results suggest that the ribosome recognizes the codon-anticodon complex by adenine contacts to the messenger RNA backbone and provide a mechanism f or molecular discrimination of correct versus incorrect codon-anticodon pai rs.