Fig. 2: Cryo-EM analysis of S. solfataricus 30S:mRNA:aIF2:Met-tRNA_i^Met complexes.

a Cryo-EM map (3.02 Å resolution) of a 30S IC complex assembled on model-SD mRNA (DS1). The Cryo-EM map is colored according to the structural model using the volume zone command in ChimeraX¹³⁷. The rRNA is in light green, except for the anti-SD sequence at the 3’-end which is in orange. R-proteins are in dark green except eS25, eS30 and eS6 which are in cornflower blue, and aS32, aS33 in Indian red. tRNA is in kaki and mRNA is in blue. The same color code is used in the four panels. b Cryo-EM map (2.8 Å resolution) of a 30S IC complex assembled on Ss-MAP lmRNA (DS2). A second mRNA molecule bound to the anti-SD sequence (see text) is colored in magenta and labeled mRNA₂. c Cryo-EM map (2.94 Å resolution) of a 30S IC complex assembled on Ss-aIF2β lmRNA (DS3). d Cryo-EM map (3.72 Å resolution) of a 30S IC complex assembled on Ss-EF1A-like lmRNA (DS4). In views (c) and (d), eS26 bound to the mRNA exit channel is colored in cornflower blue. e The structure of S. solfataricus 30S bound to Ss-aIF2β lmRNA and Met-tRNA_i^Met as observed in view (c). The view shows all 30S ribosomal proteins as discussed in the text. In the left view, Met-tRNA_i^Met is shown in light yellow cartoon. aS33, aS34 and domain 2 of eS6 were identified in this work.