Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
A biphasic pulling force acts on transmembrane helices during translocon mediated membrane integration
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
2012 (English)In: Nature Structural & Molecular Biology, ISSN 1545-9993, E-ISSN 1545-9985, Vol. 19, no 10, 1018-1022 p.Article in journal (Refereed) Published
Abstract [en]

Membrane proteins destined for insertion into the inner membrane of bacteria or the endoplasmic reticulum membrane in eukaryotic cells are synthesized by ribosomes bound to the bacterial SecYEG or the homologous eukaryotic Sec61 translocon. During co-translational membrane integration, transmembrane alpha-helical segments in the nascent chain exit the translocon through a lateral gate that opens toward the surrounding membrane, but the mechanism of lateral exit is not well understood. In particular, little is known about how a transmembrane helix behaves when entering and exiting the translocon. Using translation-arrest peptides from bacterial SecM proteins and from the mammalian Xbp1 protein as force sensors, we show that substantial force is exerted on a transmembrane helix at two distinct points during its transit through the translocon channel, providing direct insight into the dynamics of membrane integration.

Place, publisher, year, edition, pages
2012. Vol. 19, no 10, 1018-1022 p.
National Category
Biological Sciences
Research subject
Biochemistry
Identifiers
URN: urn:nbn:se:su:diva-82433DOI: 10.1038/nsmb.2376ISI: 000309591000010OAI: oai:DiVA.org:su-82433DiVA: diva2:567821
Funder
EU, European Research Council, ERC-2008-AdG 232648
Note

AuthorCount:4;

Available from: 2012-11-14 Created: 2012-11-14 Last updated: 2017-09-14Bibliographically approved
In thesis
1. Dynamics of peptide chains during co-translational translocation, membrane integration & domain folding
Open this publication in new window or tab >>Dynamics of peptide chains during co-translational translocation, membrane integration & domain folding
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The biosynthesis of proteins occurs at the ribosomes, where amino acids are linked together into linear chains. Nascent protein chains may undergo several different processes during their synthesis. Some proteins begin to fold, while others interact with chaperones, targeting factors or processing enzymes. Nascent membrane proteins are targeted to the cell membrane for integration, which involves the translocation of periplasmic domains and the insertion of membrane-embedded parts.

The aim of this thesis was to gain insights about the dynamics of nascent peptide chains undergoing folding, membrane translocation and integration. To this end, we explored the use of arrest peptides (APs) as force sensors. APs stall ribosomes when translated unless there is tension in the nascent peptide chain: the higher the tension, the more full-length protein can be detected. By using APs, we could show that a transmembrane helix is strongly ‘pulled’ twice on its way into the membrane and that strong electric forces act on negatively charged peptide segments translocating through the membrane. Furthermore, we discovered that APs could be used to detect protein folding and made the surprising discovery that a small protein domain folded well inside the ribosomal tunnel. Finally, we explored the arrest-stability of a large set of AP variants and found two extremely stable APs.

Place, publisher, year, edition, pages
Stockholm: Department of Biochemistry and Biophysics, Stockholm University, 2015. 50 p.
Keyword
ribosome, membrane integration, translocation, folding, arrest peptide, SecM
National Category
Biochemistry and Molecular Biology Cell Biology Biophysics
Research subject
Biochemistry
Identifiers
urn:nbn:se:su:diva-121764 (URN)978-91-7649-285-7 (ISBN)
Public defence
2015-12-04, Magnéli Hall, Arrhenius Laboratory, Svante arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2015-11-12 Created: 2015-10-15 Last updated: 2015-11-03Bibliographically approved
2. Insertion studies of model transmembrane segments into bacterial and eukaryotic membranes
Open this publication in new window or tab >>Insertion studies of model transmembrane segments into bacterial and eukaryotic membranes
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cells are encapsulated by a biological membrane in order to separate the cell interior from the surrounding environment. Different lipids and proteins compose the membrane and present a semi-permeable barrier for the diffusion of ions and molecules across the lipid bilayer. Membrane proteins also mediate the passage of signals between the interior and the exterior of the cell.   To ensure the proper functioning of membrane proteins, it is essential that nascent membrane proteins are correctly integrated into the lipid bilayer to be able to fold and oligomerize.  In this thesis, an engineered protein containing two natural transmembrane segments followed by an additional test segment, has been used as a model protein to study (i) sequence requirements for translocon-mediated insertion of the test segment, (ii) dynamics of nascent membrane proteins undergoing translocon-mediated insertion and (iii) to carry out an extensive mutagenesis scan to identify critical residues in the mammalian arrest peptide Xbp1 that enhances translational stalling in the ribosome. This provides a toolbox of arrest peptides with different stalling strengths that will be useful for force measurements on nascent protein chains.     

Place, publisher, year, edition, pages
Stockholm: Department of Biochemistry, Stockholm Universityand Biophysics, Stockholm University, 2017. 88 p.
Keyword
ribosome, membrane integration, translocation, arrest peptide, SecM, Xbp1
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
urn:nbn:se:su:diva-146869 (URN)978-91-7797-002-6 (ISBN)978-91-7797-003-3 (ISBN)
Public defence
2017-10-26, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.

Available from: 2017-10-03 Created: 2017-09-14 Last updated: 2017-10-04Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Ismail, NurzianHedman, RickardSchiller, Ninavon Heijne, Gunnar
By organisation
Department of Biochemistry and BiophysicsScience for Life Laboratory (SciLifeLab)
In the same journal
Nature Structural & Molecular Biology
Biological Sciences

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 95 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf