Extended Data Fig. 9: Cryo-EM image processing.
From: A tRNA modification with aminovaleramide facilitates AUA decoding in protein synthesis
a, Scheme of cryo-EM image processing, which was performed in parallel for five 70S complexes described in this study. After 3D auto-refinement and 3D classification, the subclasses of 70S ribosomes with P-site tRNA density were pooled for 3D refinement to include all particles potentially bound with P. putida tRNAIle2 at the A-site. Focused classification was performed using an A-site mask to generate the final map of the complex occupied by tRNAs at both the A- and P-sites. b,c. Fourier shell correlation curves of the complexes (b) and models vs. cryo-EM maps (c). From left to right, P. putida tRNAIle2 on A4 mRNA, dA4 mRNA, Am4 mRNA and A(F)4 mRNA, and A- and P-sites P. putida tRNAsIle2 on U4 mRNA. d, Cryo-EM densities of tRNA and mRNA codon at A-site extracted from the ribosome complex corresponding to b and c. Each map is colored according to the local resolution, and the color key is drawn on the left.
