Fig. 6. Intermediates during P/E formation are robust to A-site tRNA position.

a Tube representation of A/A (yellow) and A/P (orange; PDB: 4V7C⁹) tRNA positions. Structures are alignment based on the 23S rRNA atoms. b Tube representation of the A/P and A/P* (light blue; PDB: 4V7D⁹) structures. c Free-energy profiles reveal that the barrier separating the I1 and I2 ensembles is marginally influenced by the A-site tRNA position. d A structural snapshot illustrates how the ribosome can simultaneously accommodate tRNA molecules in the I1 (red) and A/P* (light blue) conformations.