Journal
MOLECULAR CELL
Volume 68, Issue 3, Pages 515-+Publisher
CELL PRESS
DOI: 10.1016/j.molcel.2017.10.014
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Funding
- European Regional Development Fund through the Centre of Excellence for Molecular Cell Engineering
- iNEXT - Horizon programme of the European Union [1503]
- MEYS CR [LM2015043]
- Deutsche Forschungsgemeinschaft (DFG) [GRK1721, WI3285/4-1, Forschergruppe FOR1805]
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Ribosomes synthesizing proteins containing consecutive proline residues become stalled and require rescue via the action of uniquely modified translation elongation factors, EF-P in bacteria, or archaeal/eukaryotic a/eIF5A. To date, no structures exist of EF-P or eIF5A in complex with translating ribosomes stalled at polyproline stretches, and thus structural insight into how EF-P/eIF5A rescue these arrested ribosomes has been lacking. Here we present cryo-EM structures of ribosomes stalled on proline stretches, without and with modified EF-P. The structures suggest that the favored conformation of the polyproline-containing nascent chain is incompatible with the peptide exit tunnel of the ribosome and leads to destabilization of the peptidyltRNA. Binding of EF-P stabilizes the P-site tRNA, particularly via interactions between its modification and the CCA end, thereby enforcing an alternative conformation of the polyproline-containing nascent chain, which allows a favorable substrate geometry for peptide bond formation.
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