Extended Data Fig. 2: Aminoacylated A- and P-site tRNAs bound to the A2058-methylated 70S ribosome.

(a, b, c) High-resolution (2.4Å) 2Fo-Fc electron density map (blue mesh) for the ribosome-bound A-site Phe-NH-tRNA^Phe (green) and the P-site fMet-NH-tRNA_i^Met (dark blue). The refined models of tRNAs are displayed in their respective electron density map contoured at 1.2σ. a, The entire bodies of the A- and P-site tRNAs viewed from the back of the 50S subunit, as indicated by the inset. Ribosome subunits are omitted for clarity. b, c, Close-up views of the tRNA CCA-ends carrying phenylalanyl (magenta) and formyl-methionyl (blue) moieties. Nitrogens are colored blue; oxygens are red, sulfur is yellow. In (B), H-bond between the α-amino group and the 2’-OH of the A76 of the P-site tRNA is shown with the black dotted line. This H-bond is pivotal to optimally orient α-amine for an in-line nucleophilic attack onto the carbonyl carbon of the P-site substrate. d, Superimposed models of aminoacylated tRNAs from the current 2.4Å structure of A2058-methylate 70S ribosome with the previous 2.6Å structure of A2058-unmethylated ribosome (PDB entry 1VY4³³).