Mechanism of ribosome rescue by ArfA and RF2

ArfA rescues ribosomes stalled on truncated mRNAs by recruiting release factor RF2, which normally binds stop codons to catalyze peptide release. We report two 3.2 Å resolution cryo-EM structures - determined from a single sample - of the 70S ribosome with ArfA•RF2 in the A site. In both states, the...

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Bibliographic Details
Published in:eLife 2017-03, Vol.6
Main Authors: Demo, Gabriel, Svidritskiy, Egor, Madireddy, Rohini, Diaz-Avalos, Ruben, Grant, Timothy, Grigorieff, Nikolaus, Sousa, Duncan, Korostelev, Andrei A
Format: Article
Language:English
Subjects:
ArfA
Biochemistry
Biophysics and Structural Biology
C-Terminus
Classification
Codons
Conformation
Cryoelectron Microscopy
E coli
Escherichia coli Proteins - metabolism
Escherichia coli Proteins - ultrastructure
mRNA
N-Terminus
Peptide Termination Factors - metabolism
Peptide Termination Factors - ultrastructure
Peptides
Protein Binding
Proteins
release factor 2
Release factor RF2
ribosome rescue
Ribosomes
Ribosomes - metabolism
Ribosomes - ultrastructure
RNA-Binding Proteins - metabolism
RNA-Binding Proteins - ultrastructure
stalled ribosome
Stop codon
stop-codon-independent termination
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Summary:ArfA rescues ribosomes stalled on truncated mRNAs by recruiting release factor RF2, which normally binds stop codons to catalyze peptide release. We report two 3.2 Å resolution cryo-EM structures - determined from a single sample - of the 70S ribosome with ArfA•RF2 in the A site. In both states, the ArfA C-terminus occupies the mRNA tunnel downstream of the A site. One state contains a compact inactive RF2 conformation. Ordering of the ArfA N-terminus in the second state rearranges RF2 into an extended conformation that docks the catalytic GGQ motif into the peptidyl-transferase center. Our work thus reveals the structural dynamics of ribosome rescue. The structures demonstrate how ArfA 'senses' the vacant mRNA tunnel and activates RF2 to mediate peptide release without a stop codon, allowing stalled ribosomes to be recycled.
ISSN:2050-084X
2050-084X
DOI:10.7554/eLife.23687