Mechanism of ribosome rescue by ArfA and RF2
- University of Massachusetts Medical School, United States
- Medicago, United States
- Janelia Research Campus, Howard Hughes Medical Institute, United States
- Florida State University, United States
Abstract
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.
Data availability
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3.2 A cryo-EM ArfA-RF2 ribosome rescue complex (Structure I)Publicly available at the RCSB Protein Data Bank (accession no: 5U9G).
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3.2 A cryo-EM ArfA-RF2 ribosome rescue complex (Structure I)Publicly available at EMDataBank (accession no. EMD-8522).
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3.2 A cryo-EM ArfA-RF2 ribosome rescue complex (Structure II)Publicly available at the RCSB Protein Data Bank (accession no: 5U9F).
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3.2 A cryo-EM ArfA-RF2 ribosome rescue complex (Structure II)Publicly available at EMDataBank (accession no. EMD-8521).
Article and author information
Author details
Nikolaus Grigorieff
Andrei A Korostelev
Funding
National Institutes of Health (GM106105)
- Andrei A Korostelev
National Institutes of Health (GM107465)
- Andrei A Korostelev
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2017, Demo et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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