Figure 2.

Secondary structure of natural tRNA^Phe (E. coli) showing nucleotides at which substitution of the 5′ Rp-phosphate oxygens with sulfur interferes with P-site binding at 30S subunits. Note that for phosphorothioate–interference experiments, in vitro transcribed tRNAs lacking the indicated natural modifications were used, whereas for ENU modification–interference experiments natural tRNAs were taken. Large and small circles indicate strong and weak interference, respectively; open circles indicate interference strongly dependent on mRNA presence. The filled rectangle indicates enrichment of tRNAs containing a Rp-phosphorothioates at position 34. Triangles indicate positions of interference when ethylated by ENU.