Alignment of Conduits for the Nascent Polypeptide Chain in the Ribosome-Sec61 Complex
10.1126/science.278.5346.2123
Crossref journal-article
American Association for the Advancement of Science (AAAS)
Science (221)
Abstract

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.

Bibliography

Beckmann, R., Bubeck, D., Grassucci, R., Penczek, P., Verschoor, A., Blobel, G., & Frank, J. (1997). Alignment of Conduits for the Nascent Polypeptide Chain in the Ribosome-Sec61 Complex. Science, 278(5346), 2123–2126.

Authors 7
  1. Roland Beckmann (first)
  2. Doryen Bubeck (additional)
  3. Robert Grassucci (additional)
  4. Pawel Penczek (additional)
  5. Adriana Verschoor (additional)
  6. Günter Blobel (additional)
  7. Joachim Frank (additional)
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  35. ]. In both cases four steps of the 3D projection alignment procedure (19) were applied with a 2° angular interval. In each step the refined 3D structure was calculated with 70% of the best matching particles (on the basis of the value of the cross-correlation coefficient). Both reconstructions proved to be indistinguishable within the measured resolution range. The final resolution estimated with the Fourier shell correlation with a cutoff value at 0.5 [
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  39. In trying to gauge the correct threshold value we were led by two criteria: (i) We observed the structure as the threshold was increased. There is normally a “plateau ” a range of threshold values within which the appearance (or the volume encompassed) varies only slightly. (ii) Three-dimensional connectivity must not be violated which means that in this case we could not choose a threshold within the plateau defined above that makes the connecting rod disappear. Thus the plateau was further narrowed. These criteria were applied separately in the preparation of the 3D representations of the ribosome and the channel. Because of the residual uncertainty in the molecular boundaries the measurements for pore size and the distance between channel and ribosome have an uncertainty of 25%.
  40. We thank A. Fischer for the purification of the Sec61 complex; members of the Blobel lab and R. Agrawal for discussions; S. Darst and A. Malhotra for discussions support with the electron microscopy and assistance with the image processing; A. Heagle for help with the illustrations; and the National Center for Supercomputer Applications University of Illinois at Urbana-Champaign for computing support. Supported by grants from NIH (1R01 GM29169) and NSF (BIR 9219043) (to J.F.) and a fellowship of the Deutsche Foschungsgemeinschaft (to R.B.).
Dates
Type When
Created 23 years, 1 month ago (July 27, 2002, 5:50 a.m.)
Deposited 1 year, 7 months ago (Jan. 12, 2024, 11:55 p.m.)
Indexed 1 month, 3 weeks ago (July 2, 2025, 2:31 p.m.)
Issued 27 years, 8 months ago (Dec. 19, 1997)
Published 27 years, 8 months ago (Dec. 19, 1997)
Published Print 27 years, 8 months ago (Dec. 19, 1997)
Funders 0

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@article{Beckmann_1997, title={Alignment of Conduits for the Nascent Polypeptide Chain in the Ribosome-Sec61 Complex}, volume={278}, ISSN={1095-9203}, url={http://dx.doi.org/10.1126/science.278.5346.2123}, DOI={10.1126/science.278.5346.2123}, number={5346}, journal={Science}, publisher={American Association for the Advancement of Science (AAAS)}, author={Beckmann, Roland and Bubeck, Doryen and Grassucci, Robert and Penczek, Pawel and Verschoor, Adriana and Blobel, Günter and Frank, Joachim}, year={1997}, month=dec, pages={2123–2126} }