Structures of tmRNA and SmpB as they transit through the ribosome.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 34389707.
- Also identified by DOI 10.1038/s41467-021-24881-4 and PMC identifier 8363625.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
In bacteria, trans-translation is the main rescue system, freeing ribosomes stalled on defective messenger RNAs. This mechanism is driven by small protein B (SmpB) and transfer-messenger RNA (tmRNA), a hybrid RNA known to have both a tRNA-like and an mRNA-like domain. Here we present four cryo-EM structures of the ribosome during trans-translation at resolutions from 3.0 to 3.4 Å. These include the high-resolution structure of the whole pre-accommodated state, as well as structures of the accommodated state, the translocated state, and a translocation intermediate. Together, they shed light on the movements of the tmRNA-SmpB complex in the ribosome, from its delivery by the elongation factor EF-Tu to its passage through the ribosomal A and P sites after the opening of the B1 bridges. Additionally, we describe the interactions between the tmRNA-SmpB complex and the ribosome. These explain why the process does not interfere with canonical translation.
Medical subject headings
- Escherichia coli
- Escherichia coli Proteins
- Protein Biosynthesis
- RNA, Bacterial
- RNA-Binding Proteins
- Ribosomes