Note to users. If you're seeing this message, it means that your browser cannot find this page's style/presentation instructions -- or possibly that you are using a browser that does not support current Web standards. Find out more about why this message is appearing, and what you can do to make your experience of our site the best it can be.

Originally published in Science Express on 29 October 2009
Science 4 December 2009:
Vol. 326. no. 5958, pp. 1369 - 1373
DOI: 10.1126/science.1178535
Prev | Table of Contents | Next

Research Articles

Structure of Monomeric Yeast and Mammalian Sec61 Complexes Interacting with the Translating Ribosome

Thomas Becker,1 Shashi Bhushan,1 Alexander Jarasch,1 Jean-Paul Armache,1 Soledad Funes,1,2 Fabrice Jossinet,3 James Gumbart,4 Thorsten Mielke,5,6 Otto Berninghausen,1 Klaus Schulten,4 Eric Westhof,3 Reid Gilmore,7 Elisabet C. Mandon,7,* Roland Beckmann1,*

The trimeric Sec61/SecY complex is a protein-conducting channel (PCC) for secretory and membrane proteins. Although Sec complexes can form oligomers, it has been suggested that a single copy may serve as an active PCC. We determined subnanometer-resolution cryo–electron microscopy structures of eukaryotic ribosome-Sec61 complexes. In combination with biochemical data, we found that in both idle and active states, the Sec complex is not oligomeric and interacts mainly via two cytoplasmic loops with the universal ribosomal adaptor site. In the active state, the ribosomal tunnel and a central pore of the monomeric PCC were occupied by the nascent chain, contacting loop 6 of the Sec complex. This provides a structural basis for the activity of a solitary Sec complex in cotranslational protein translocation.

1 Gene Center Munich and Center for Integrated Protein Science, Department of Chemistry and Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany.
2 Departamento de Bioquímica, Instituto de Fisiología Celular, Circuito Exterior s/n, Ciudad Universitaria, Universidad Nacional Autónoma de México, Mexico, Distrito Federal, 04510, Mexico.
3 Institut de Biologie Moléculaire et Cellulaire du CNRS, Architecture et Réactivité de l’ARN, Université de Strasbourg, 15 rue René Descartes, F-67084 Strasbourg, France.
4 Department of Physics, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
5 Ultrastrukturnetzwerk, Max Planck Institute for Molecular Genetics, Ihnestrasse 63-73, D-14195 Berlin, Germany.
6 Institut für Medizinische Physik und Biophysik, Charite–Universitätsmedizin Berlin, Ziegelstrasse 5-9, 10117-Berlin, Germany.
7 Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA.

* To whom correspondence should be addressed. E-mail: elisabet.mandon{at}umassmed.edu (E.M.); beckmann{at}lmb.uni-muenchen.de (R.B.)

Read the Full Text


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Nascent Proteins Caught in the Act.
M. Kampmann and G. Blobel (2009)
Science 326, 1352-1353
   Abstract »    Full Text »    PDF »
Structural Insight into Nascent Polypeptide Chain-Mediated Translational Stalling.
B. Seidelt, C. A. Innis, D. N. Wilson, M. Gartmann, J.-P. Armache, E. Villa, L. G. Trabuco, T. Becker, T. Mielke, K. Schulten, et al. (2009)
Science 326, 1412-1415
   Abstract »    Full Text »    PDF »


To Advertise     Find Products

Science. ISSN 0036-8075 (print), 1095-9203 (online)