Fig. 9: Close-up of the mRNA path during trans-translation.
From: Structures of tmRNA and SmpB as they transit through the ribosome
In the a pre-accommodation and b accommodation states, the C-terminal tail of SmpB (purple) occupies the mRNA channel, while the H5 stem-loop of tmRNA (red) closes the entrance. Both domains would clash with a canonical mRNA (yellow, PDB code 6ZTJ88), forcing the selection of stalled ribosomes. c After translocation, the C-terminal tail is rotated by 62° and deeply inserted into the mRNA exit tunnel. There again, it clashes with the mRNA (PDB code 7JT189), resulting in the ejection of the non-stop mRNA from the ribosome. The cryo-electron density map of the 30S small subunit is shown as a white surface.
