EMD-22470

Single-particle
3.2 Å
EMD-22470 Deposition: 16/08/2020
Map released: 11/11/2020
Last modified: 02/12/2020
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links

EMD-22470

70S ribosome stalled on long mRNA with ArfB bound in the A site (+9-VI)

EMD-22470

Single-particle
3.2 Å
EMD-22470 Deposition: 16/08/2020
Map released: 11/11/2020
Last modified: 02/12/2020
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links
Sample Organism: Escherichia coli K-12
Sample: 70S ribosome stalled on long mRNA with ArfB bound in the A site (+9-VI)

Deposition Authors: Carbone CE, Korostelev AA
ArfB can displace mRNA to rescue stalled ribosomes.
Carbone CE, Demo G , Madireddy R, Svidritskiy E, Korostelev AA
(2020) Nat Commun , 11 , 5552 - 5552
PUBMED: 33144582
DOI: doi:10.1038/s41467-020-19370-z
ISSN: 2041-1723
Abstract:
Ribosomes stalled during translation must be rescued to replenish the pool of translation-competent ribosomal subunits. Bacterial alternative rescue factor B (ArfB) releases nascent peptides from ribosomes stalled on mRNAs truncated at the A site, allowing ribosome recycling. Prior structural work revealed that ArfB recognizes such ribosomes by inserting its C-terminal α-helix into the vacant mRNA tunnel. In this work, we report that ArfB can efficiently recognize a wider range of mRNA substrates, including longer mRNAs that extend beyond the A-site codon. Single-particle cryo-EM unveils that ArfB employs two modes of function depending on the mRNA length. ArfB acts as a monomer to accommodate a shorter mRNA in the ribosomal A site. By contrast, longer mRNAs are displaced from the mRNA tunnel by more than 20 Å and are stabilized in the intersubunit space by dimeric ArfB. Uncovering distinct modes of ArfB function resolves conflicting biochemical and structural studies, and may lead to re-examination of other ribosome rescue pathways, whose functions depend on mRNA lengths.