Format

Send to

Choose Destination
Elife. 2017 Mar 16;6. pii: e23687. doi: 10.7554/eLife.23687.

Mechanism of ribosome rescue by ArfA and RF2.

Author information

1
RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, United States.
2
Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, United States.
3
Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States.
4
Department of Biological Science, Florida State University, Tallahassee, 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.

KEYWORDS:

ArfA; E. coli; biochemistry; biophysics; release factor 2; ribosome rescue; stalled ribosome; stop-codon-independent termination; structural biology

PMID:
28300532
PMCID:
PMC5378476
DOI:
10.7554/eLife.23687
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for eLife Sciences Publications, Ltd Icon for PubMed Central
Loading ...
Support Center