Fig. 3: Cryo-EM structure of the GE-30S initiation intermediate complex.

a Refined map of GE-30S complex with IF1 (red) and IF3 (blue) with a transverse section showing the mRNA (green) with density for the Shine Dalgarno (SD)-antiSD (SD-aSD) helix. b Postprocessed cryo-EM map of GE-30S complex with GE (cyan), IF1 (red), IF3 (blue), and with the 30S head removed from map and shown as a silhouette. c Cryo-EM map density (transparent grey) for GE (cyan) shown from postprocessed map. An asterisk is shown on carbon with correct stereochemistry determined here. d Helices of 16S rRNA which interact with Ede include h24 (salmon), h44 (dark grey) and ribosomal protein uS11 (orange). e Putative hydrogen bond interactions (dashed lines) between GE and the 16S rRNA nucleotides (grey) and uS11 (orange). f Putative water-mediated interactions of GE with 30S subunit are shown as cyan dashed lines with cryo-EM density (grey mesh) shown for the modelled water molecules (red spheres). g Overlay of mRNA path (green) of GE (cyan) and 16S rRNA (grey) with density (transparent). mRNA positions are marked relative to the P site codon (first position as +1). h Overlay of mRNA path (yellow) from 30S-PIC (PDB ID 5LMN)⁶ showing a clash (red) with GE (cyan). i Overlay of mRNA path (salmon) and tRNA^fMet (orange) from 30S-IC (PDB ID 5LMV)⁶ showing a clash (red) with GE (cyan).