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  • Cryoelectron Microscopy  (2)
  • 1
    Publication Date: 2012-02-24
    Description: Ribosome-driven protein biosynthesis is comprised of four phases: initiation, elongation, termination and recycling. In bacteria, ribosome recycling requires ribosome recycling factor and elongation factor G, and several structures of bacterial recycling complexes have been determined. In the eukaryotic and archaeal kingdoms, however, recycling involves the ABC-type ATPase ABCE1 and little is known about its structural basis. Here we present cryo-electron microscopy reconstructions of eukaryotic and archaeal ribosome recycling complexes containing ABCE1 and the termination factor paralogue Pelota. These structures reveal the overall binding mode of ABCE1 to be similar to canonical translation factors. Moreover, the iron-sulphur cluster domain of ABCE1 interacts with and stabilizes Pelota in a conformation that reaches towards the peptidyl transferase centre, thus explaining how ABCE1 may stimulate peptide-release activity of canonical termination factors. Using the mechanochemical properties of ABCE1, a conserved mechanism in archaea and eukaryotes is suggested that couples translation termination to recycling, and eventually to re-initiation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Becker, Thomas -- Franckenberg, Sibylle -- Wickles, Stephan -- Shoemaker, Christopher J -- Anger, Andreas M -- Armache, Jean-Paul -- Sieber, Heidemarie -- Ungewickell, Charlotte -- Berninghausen, Otto -- Daberkow, Ingo -- Karcher, Annette -- Thomm, Michael -- Hopfner, Karl-Peter -- Green, Rachel -- Beckmann, Roland -- U19 AI083025/AI/NIAID NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2012 Feb 22;482(7386):501-6. doi: 10.1038/nature10829.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Gene Center and Center for integrated Protein Science Munich, Department of Biochemistry, University of Munich, Feodor-Lynen-Strasse 25, 81377 Munich, Germany. becker@lmb.uni-muenchen.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22358840" target="_blank"〉PubMed〈/a〉
    Keywords: ATP-Binding Cassette Transporters/chemistry/metabolism ; Cell Cycle Proteins/chemistry/metabolism ; Cryoelectron Microscopy ; Endoribonucleases/chemistry/metabolism ; *Evolution, Molecular ; Iron-Sulfur Proteins/chemistry/metabolism ; Models, Molecular ; Movement ; Multiprotein Complexes/chemistry/metabolism ; Nuclear Proteins/chemistry/metabolism ; Peptide Termination Factors/chemistry/metabolism ; Protein Binding ; Protein Stability ; Protein Structure, Tertiary ; Pyrococcus furiosus/*chemistry/metabolism ; Ribosomes/*chemistry/*metabolism/ultrastructure ; Saccharomyces cerevisiae/*chemistry/metabolism ; Saccharomyces cerevisiae Proteins/chemistry/metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2014-02-07
    Description: The biogenesis of secretory as well as transmembrane proteins requires the activity of the universally conserved protein-conducting channel (PCC), the Sec61 complex (SecY complex in bacteria). In eukaryotic cells the PCC is located in the membrane of the endoplasmic reticulum where it can bind to translating ribosomes for co-translational protein transport. The Sec complex consists of three subunits (Sec61alpha, beta and gamma) and provides an aqueous environment for the translocation of hydrophilic peptides as well as a lateral opening in the Sec61alpha subunit that has been proposed to act as a gate for the membrane partitioning of hydrophobic domains. A plug helix and a so-called pore ring are believed to seal the PCC against ion flow and are proposed to rearrange for accommodation of translocating peptides. Several crystal and cryo-electron microscopy structures revealed different conformations of closed and partially open Sec61 and SecY complexes. However, in none of these samples has the translocation state been unambiguously defined biochemically. Here we present cryo-electron microscopy structures of ribosome-bound Sec61 complexes engaged in translocation or membrane insertion of nascent peptides. Our data show that a hydrophilic peptide can translocate through the Sec complex with an essentially closed lateral gate and an only slightly rearranged central channel. Membrane insertion of a hydrophobic domain seems to occur with the Sec complex opening the proposed lateral gate while rearranging the plug to maintain an ion permeability barrier. Taken together, we provide a structural model for the basic activities of the Sec61 complex as a protein-conducting channel.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gogala, Marko -- Becker, Thomas -- Beatrix, Birgitta -- Armache, Jean-Paul -- Barrio-Garcia, Clara -- Berninghausen, Otto -- Beckmann, Roland -- England -- Nature. 2014 Feb 6;506(7486):107-10. doi: 10.1038/nature12950.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Gene Center and Center for integrated Protein Science Munich, Department of Biochemistry, Feodor-Lynen-Strasse 25, University of Munich, 81377 Munich, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24499919" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Membrane/*metabolism/ultrastructure ; Cryoelectron Microscopy ; Dogs ; Hydrophobic and Hydrophilic Interactions ; Membrane Proteins/chemistry/*metabolism/*ultrastructure ; Models, Molecular ; Multiprotein Complexes/chemistry/metabolism/*ultrastructure ; Peptides/chemistry/*metabolism ; *Protein Biosynthesis ; Protein Subunits/*chemistry/metabolism ; Protein Transport ; Ribosomes/chemistry/*metabolism/ultrastructure
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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