Visualizing tmRNA Entry into a Stalled Ribosome

@article{Valle2003VisualizingTE,
  title={Visualizing tmRNA Entry into a Stalled Ribosome},
  author={Mikel Valle and Reynald Gillet and Sukhjit Kaur and Anke Henne and Venkatraman Ramakrishnan and Joachim Frank},
  journal={Science},
  year={2003},
  volume={300},
  pages={127 - 130}
}
Bacterial ribosomes stalled on defective messenger RNAs (mRNAs) are rescued by tmRNA, an ∼300-nucleotide-long molecule that functions as both transfer RNA (tRNA) and mRNA. Translation then switches from the defective message to a short open reading frame on tmRNA that tags the defective nascent peptide chain for degradation. However, the mechanism by which tmRNA can enter and move through the ribosome is unknown. We present a cryo–electron microscopy study at ∼13 to 15 angstroms of the entry of… 
tmRNA on its way through the ribosome
TLDR
Determination of the structure of tmRNA and SmpB in complex with the ribosome, at the stage when translation has resumed on tmRNAs, has provided an increased understanding and unique insights into the complex mechanism of template switching on the Ribosome and Sm pB-driven selection of the correct reading frame on t mRNA’s ORF.
Structural features of the tmRNA-ribosome interaction.
TLDR
Computer modeling has been used to develop a model for spatial organization of the tmRNA inside the ribosome at different stages of trans-translation, and it is exploited to examine the t mRNA structure using chemical probing and cryo-electron microscopy tomography.
Structures of tmRNA and SmpB as they transit through the ribosome
TLDR
Four cryo-EM structures of the ribosome during trans-translation are presented and light is shed on the movements of the tmRNA-SmpB complex in theribosome, 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.
Cryo-EM visualization of transfer messenger RNA with two SmpBs in a stalled ribosome
TLDR
A density map for the preaccommodated state of the tmRNA·SmpB·EF-Tu·70S ribosome complex is obtained with much improved definition for the TLD, showing two SmpB molecules bound per ribosomes, one toward the A site on the 30S sub unit side and the other bound to the 50S subunit near the GTPase-associated center.
Accommodation of tmRNA-SmpB into stalled ribosomes: a cryo-EM study.
TLDR
Using a construct containing the tRNA-like domain as well as the extended helix H2 of tm RNA, a cryo-electron microscopy study of the process of accommodation is presented and suggests that the larger movement required to resume translation on a tmRNA internal open reading frame starts during accommodation.
The tmRNA ribosome-rescue system.
Dial tm for rescue: tmRNA engages ribosomes stalled on defective mRNAs.
Visualizing the transfer-messenger RNA as the ribosome resumes translation
TLDR
This study obtained the first structure of an in vivo‐formed complex containing ribosome and the tmRNA at the point where the TLD is accommodated into the ribosomal P site, and built an atomic model, which suggests that SmpB interacts with the five nucleotides immediately upstream of the resume codon, thereby determining the correct selection of the reading frame on the ORF of tm RNA.
The tmRNA system for translational surveillance and ribosome rescue.
TLDR
Structural and biochemical studies suggest mechanisms that keep tmRNA from interrupting normal translation and target ribosomes stalled with very short 3' mRNA extensions.
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