Fig. 1

Structures of RF1- and RF3-containing termination complexes. a–f Schematic representation (above) and electron density (below) for termination complexes containing a RF1 (orange) stalled by API on a non-rotated ribosome with a classical P/P-site tRNA (green)²⁶, b RF3 (cyan) trapped by GDPCP on a rotated ribosome with hybrid P/E-site tRNA²⁸, c–f state I–IV with RF1-GAQ (orange), RF3-GDPCP (cyan) bound to c–e partially rotated ribosomes with intermediate P-site (P_int) tRNA (green) or f a fully rotated ribosome with a hybrid P/E-site tRNA (green). In the scheme, the SSU and LSU are coloured yellow and grey, respectively, with A-, P- and E-sites and the L1 stalk indicated, whereas flexible regions are indicated by increased transparency. In the map overviews, the electron density for the SSU and LSU has been filtered locally and is shown as a grey transparency so that the ligands can be easily seen within the ribosome