(a,b) Comparison of the 80S ribosome complexes with the CHX ligand or with E-site tRNA bound in the sample separated by particle sorting, showing the conformational changes of the L1 region on the ribosome occurring upon CHX binding and tRNA release (left, 80S/CHX complex; right, 80S with E-site tRNA, middle superposition; cryo-EM maps and corresponding atomic models are shown in blue and green respectively). The structural disorder of the L1 region upon CHX binding and tRNA release is illustrated by the fact that it is better visible in cryo-EM maps filtered to 5 Å (b) compared with the full-resolution maps (a). (c) Overall binding region of CHX on the human 80S ribosome (backbone representation; CHX is shown with van der Waals spheres); the L1 region is disordered because of the absence of E-site tRNA. The inset shows the overall cryo-EM map sectioned at the level of the ligand-binding pocket (arrow; 60S and 40S subunits are annotated). (d) Structural comparison with the human 80S ribosome containing E-site tRNA10. View on the exit (E) site tRNA including the rRNA components interacting with the tRNA (marked in red) which are well-structured including the L1 region.