Structures du complexe ARNtm-SmpB lors de sa traversée du ribosome.
In bacteria, trans-translation is the main quality control system for releasing ribosomes stuck on defective messenger RNAs.
This mechanism is carried by small protein B (SmpB) and transfer-messenger RNA (tRNA), a unique hybrid RNA with both tRNA and mRNA properties.
IGDR scientists have solved four high-resolution ribosome structures, from 3.0 to 3.4 Å, using cryo-electron microscopy (cryo-EM).These include structures of the pre-accommodated, accommodated and translocated states, as well as a novel translocation intermediate.
Together, they shed light on the movements of the gRNA-SmpB complex in the ribosome, from its arrival at the ribosome carried by the elongation factor EF-Tu to its passage through the A and P ribosomal sites after the opening of the B1 bridges.
The interactions between the gRNA-SmpB complex and the ribosome are also described at the atomic scale. These explain why the process does not interfere with canonical translation.
We hope that these structures will serve as a basis for the development of new antibiotics targeting the trans-translation process.
Nature Communication : Structures of tmRNA and SmpB as they transit through the ribosome. Nat. Comm.