Fig. 4. Structure of iboxamycin (IBX) bound to the Erm-methylated 70S ribosome.

a, b, Electron density map (blue mesh), contoured at 1.0σ, of IBX (teal) in complex with the Erm-modified T. thermophilus 70S ribosome-containing N⁶-dimethylated A2058 residue in the 23S rRNA (a), highlighting the interaction with the methyl groups of ${\text{m}}_2^6\text{A}2058$ (orange) (b). c, d, Superposition of IBX (yellow) in complex with the WT 70S ribosome containing an unmodified residue A2058 (light blue), and the structure of IBX (teal) in complex with the Erm-modified 70S ribosome containing an ${\text{m}}_2^6\text{A}2058$ residue (medium blue) (c), highlighting hydrogen bonding (dashed lines) (d). Note that the position of IBX is almost identical in the two structures, whereas IBX binding to the Erm-modified ribosome causes substantial movement of ${\text{m}}_2^6\text{A}2058$ from its canonical position (red arrow). WT, wild type.