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Charge-driven dynamics of nascent-chain movement through the SecYEG translocon
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).
2015 (English)In: Nature Structural & Molecular Biology, ISSN 1545-9993, E-ISSN 1545-9985, Vol. 22, no 2, 145-149 p.Article in journal (Refereed) Published
Abstract [en]

On average, every fifth residue in secretory proteins carries either a positive or a negative charge. In a bacterium such as Escherichia coli, charged residues are exposed to an electric field as they transit through the inner membrane, and this should generate a fluctuating electric force on a translocating nascent chain. Here, we have used translational arrest peptides as in vivo force sensors to measure this electric force during cotranslational chain translocation through the SecYEG translocon. We find that charged residues experience a biphasic electric force as they move across the membrane, including an early component with a maximum when they are 47-49 residues away from the ribosomal P site, followed by a more slowly varying component. The early component is generated by the transmembrane electric potential, whereas the second may reflect interactions between charged residues and the periplasmic membrane surface.

Place, publisher, year, edition, pages
2015. Vol. 22, no 2, 145-149 p.
National Category
Biological Sciences
Research subject
Biochemistry
Identifiers
URN: urn:nbn:se:su:diva-115293DOI: 10.1038/nsmb.2940ISI: 000348967400010PubMedID: 25558985OAI: oai:DiVA.org:su-115293DiVA: diva2:799904
Note

AuthorCount:4;

Available from: 2015-03-31 Created: 2015-03-18 Last updated: 2017-12-04Bibliographically 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

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