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Nat Struct Mol Biol. 2010 Mar;17(3):313-7. doi: 10.1038/nsmb.1756. Epub 2010 Feb 7.

alpha-Helical nascent polypeptide chains visualized within distinct regions of the ribosomal exit tunnel.

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Gene Center and Center for Integrated Protein Science Munich, Department of Biochemistry, University of Munich, Munich, Germany.


As translation proceeds, the nascent polypeptide chain passes through a tunnel in the large ribosomal subunit. Although this ribosomal exit tunnel was once thought only to be a passive conduit for the growing nascent chain, accumulating evidence suggests that it may in fact play a more active role in regulating translation and initial protein folding events. Here we have determined single-particle cryo-electron microscopy reconstructions of eukaryotic 80S ribosomes containing nascent chains with high alpha-helical propensity located within the exit tunnel. The maps enable direct visualization of density for helices as well as allowing the sites of interaction with the tunnel wall components to be elucidated. In particular regions of the tunnel, the nascent chain adopts distinct conformations and establishes specific contacts with tunnel components, both ribosomal RNA and proteins, that have been previously implicated in nascent chain-ribosome interaction.

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