5MGP

Structural basis for ArfA-RF2 mediated translation termination on stop-codon lacking mRNAs

This is a non-PDB format compatible entry.

Summary for 5MGP

• Entry DOI: 10.2210/pdb5mgp/pdb
• EMDB information: 3508
• Descriptor: 23S ribosomal RNA, 50S ribosomal protein L14, 50S ribosomal protein L15, ... (56 entities in total)
• Functional Keywords: cryo-em, ribosome, termination, alternative rescue factor a
• Biological source: Escherichia coli; More
• Cellular location: Cytoplasm: P07012
• Total number of polymer chains: 56
• Total formula weight: 2184504.98

Authors

Huter, P.,Mueller, C.,Beckert, B.,Arenz, S.,Berninghausen, O.,Beckmann, R.,Wilson, N.D. (deposition date: 2016-11-21, release date: 2016-12-14, Last modification date: 2024-10-23)

Primary citation

Huter, P.,Muller, C.,Beckert, B.,Arenz, S.,Berninghausen, O.,Beckmann, R.,Wilson, D.N.
Structural basis for ArfA-RF2-mediated translation termination on mRNAs lacking stop codons.
Nature, 541:546-549, 2017

PubMed Abstract: In bacteria, ribosomes stalled on truncated mRNAs that lack a stop codon are rescued by the transfer-messenger RNA (tmRNA), alternative rescue factor A (ArfA) or ArfB systems. Although tmRNA-ribosome and ArfB-ribosome structures have been determined, how ArfA recognizes the presence of truncated mRNAs and recruits the canonical termination release factor RF2 to rescue the stalled ribosomes is unclear. Here we present a cryo-electron microscopy reconstruction of the Escherichia coli 70S ribosome stalled on a truncated mRNA in the presence of ArfA and RF2. The structure shows that the C terminus of ArfA binds within the mRNA entry channel on the small ribosomal subunit, and explains how ArfA distinguishes between ribosomes that bear truncated or full-length mRNAs. The N terminus of ArfA establishes several interactions with the decoding domain of RF2, and this finding illustrates how ArfA recruits RF2 to the stalled ribosome. Furthermore, ArfA is shown to stabilize a unique conformation of the switch loop of RF2, which mimics the canonical translation termination state by directing the catalytically important GGQ motif within domain 3 of RF2 towards the peptidyl-transferase centre of the ribosome. Thus, our structure reveals not only how ArfA recruits RF2 to the ribosome but also how it promotes an active conformation of RF2 to enable translation termination in the absence of a stop codon.

PubMed: 27906161
DOI: 10.1038/nature20821

Experimental method

ELECTRON MICROSCOPY (3.1 Å)