Fitting of the 30S subunit, A- and P-site tRNAs, and PKF–SmpB into the cryo-EM map of the accommodated state. (A) Cryo-EM map of the 30S subunit (yellow), with the densities corresponding to TLD–SmpB complex in red and tRNAfMet in purple. The fitted 30S crystal structure from T. thermophilus with canonical tRNAs in A- and P-sites is shown in ribbon inside the map (yellow, 30S subunit; red, A-site tRNA; blue, P-site tRNA). (B) Superimposition of the acceptor arm from A-site tRNA with the one from the crystal structure of the TLD–SmpB complex. (red, A-site tRNA; light green, TLD; black, SmpB). (C) Substitution of the A-site tRNA by the TLD–SmpB atomic model in the cryo-EM map. The coordinates for helix H2 (dark green) were satisfactorily docked into the unexplained region. Landmarks on 30S subunit are: b, beak; dc, decoding center; sh, shoulder; sp, spur. For clarity, 50S subunit is not shown.