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Huter, Paul; Arenz, Stefan; Bock, Lars V.; Graf, Michael; Frister, Jan Ole; Heuer, Andre; Peil, Lauri; Starosta, Agata L.; Wohlgemuth, Ingo; Peske, Frank; Novacek, Jiri; Berninghausen, Otto; GrubMüller, Helmut; Tenson, Tanel; Beckmann, Roland; Rodnina, Marina V.; Vaiana, Andrea C.; Wilson, Daniel N. (2017): Structural Basis for Polyproline-Mediated Ribosome Stalling and Rescue by the Translation Elongation Factor EF-P. In: Molecular Cell, Vol. 68, No. 3: pp. 515-527
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Abstract

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.