Figure 3: Cryo-EM map-fitted atomic model of the 70S ribosome bound with Tet(O).

(a) Cryo-EM map, displayed as transparent mesh, with atomic model displayed as ribbons. The 16S rRNA is in yellow, proteins in the 30S subunit in green, 5S and 23S rRNA in blue, and proteins in the 50S subunit in pink. Tet(O) is in red, P-site tRNA in dark green. (b) The 30S subunit with Tet(O) and P-site tRNA shown in a is displayed after a clockwise rotation around vertical (in plane) axis by 90°, to show the interface with the 50S subunit. (c) Tet(O)’s domain IV (red), superimposed with the anticodon stem and loop of an A/T-site tRNA (grey) in the decoding region of the 30S subunit. The overlap between Tet(O) and the tRNA occurs at the 507- and 438-loops. (d) Zoomed-in view of the area marked by green box in b. (e) Portion of the 16S rRNA (pink) surrounding Tc, superimposed on the 16S rRNA (yellow) in the current Tet(O)-bound model. The 507-loop is seen to clash with the site for Tc (blue). Nucleotides 1051 and 1054 in the 16S rRNA are seen to be reoriented in the two structures. (f) The 507-loop, 438-loop and a portion of the 30S subunit including nucleotides 966, 1196 and their surrounding nts form a structural corridor for a possible release of Tc. (g) Tet(O)-S12 contact sites. S12 is shown in dark green.