Alignment of Conduits for the Nascent Polypeptide Chain in the Ribosome-Sec61 Complex

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Science  19 Dec 1997:
Vol. 278, Issue 5346, pp. 2123-2126
DOI: 10.1126/science.278.5346.2123

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An oligomer of the Sec61 trimeric complex is thought to form the protein-conducting channel for protein transport across the endoplasmic reticulum. A purified yeast Sec61 complex bound to monomeric yeast ribosomes as an oligomer in a saturable fashion. Cryo–electron microscopy of the ribosome-Sec61 complex and a three-dimensional reconstruction showed that the Sec61 oligomer is attached to the large ribosomal subunit by a single connection. Moreover, a funnel-shaped pore in the Sec61 oligomer aligned with the exit of a tunnel traversing the large ribosomal subunit, strongly suggesting that both structures function together in the translocation of proteins across the endoplasmic reticulum membrane.

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