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Structure and dynamics of plant TatA in micelles and lipid bilayers studied by solution NMR
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
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Number of Authors: 62018 (English)In: The FEBS Journal, ISSN 1742-464X, E-ISSN 1742-4658, Vol. 285, no 10, p. 1886-1906Article in journal (Refereed) Published
Abstract [en]

The twin-arginine translocase (Tat) transports folded proteins across the cytoplasmic membrane of prokaryotes and the thylakoid membrane of plant chloroplasts. In Gram-negative bacteria and chloroplasts, the translocon consists of three subunits, TatA, TatB, and TatC, of which TatA is responsible for the actual membrane translocation of the substrate. Herein we report on the structure, dynamics, and lipid interactions of a fully functional C-terminally truncated core TatA' from Arabidopsisthaliana using solution-state NMR. Our results show that TatA consists of a short N-terminal transmembrane helix (TMH), a short connecting linker (hinge) and a long region with propensity to form an amphiphilic helix (APH). The dynamics of TatA were characterized using N-15 relaxation NMR in combination with model-free analysis. The TMH has order parameters characteristic of a well-structured helix, the hinge is somewhat less rigid, while the APH has lower order parameters indicating structural flexibility. The TMH is short with a surprisingly low protection from solvent, and only the first part of the APH is protected to some extent. In order to uncover possible differences in TatA's structure and dynamics in detergent compared to in a lipid bilayer, fast-tumbling bicelles and large unilamellar vesicles were used. Results indicate that the helicity of TatA increases in both the TMH and APH in the presence of lipids, and that the N-terminal part of the TMH is significantly more rigid. The results indicate that plant TatA has a significant structural plasticity and a capability to adapt to local environments.

Place, publisher, year, edition, pages
2018. Vol. 285, no 10, p. 1886-1906
Keywords [en]
bicelle, dynamics, membrane mimetics, micelle, model-free approach, paramagnetic relaxation enhancement, relaxation, structure, TatA, twin-arginine translocation
National Category
Biological Sciences
Research subject
Biophysics
Identifiers
URN: urn:nbn:se:su:diva-157788DOI: 10.1111/febs.14452ISI: 000434177700011PubMedID: 29654717OAI: oai:DiVA.org:su-157788DiVA, id: diva2:1235575
Available from: 2018-07-26 Created: 2018-07-26 Last updated: 2019-04-05Bibliographically approved
In thesis
1. Structure, dynamics and lipid interaction of membrane-associated proteins
Open this publication in new window or tab >>Structure, dynamics and lipid interaction of membrane-associated proteins
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A research topic within the field of molecular biophysics is the structure-function relationship of proteins. Membrane proteins are a large, diverse group of biological macromolecules that perform many different and essential functions for the cell. Despite the abundance and importance of membrane proteins, high-resolution 3D structures from this class of proteins are underrepresented among all yet determined structures. The limited amount of data for membrane proteins hints about the higher difficulty associated with studies of this group of molecules. The determination of an atomic resolution structure is often a long process in which several obstacles need to be overcome, in particular for membrane proteins.

Solution-state nuclear magnetic resonance (NMR) is a powerful measurement technique that can provide high-resolution data on the structure and dynamics of biological macromolecules, and is suitable for studies of small, dynamic membrane proteins. However, even with solution-state NMR, the membrane proteins need to be investigated in environments that are sometimes severely compromising for the protein’s native structure and function. In order to evaluate the biological significance of results obtained under such artificial conditions, supporting data from experiments in more realistic membrane models, obtained using NMR and other biophysical methods, is of great importance.

The work presented in this thesis concerns studies of four membrane proteins: WaaG, Rcf1, Rcf2 and TatA. These proteins have very different characteristics in terms of their sizes and expected membrane interactions, and were accordingly found to be differently affected by the model membranes in which they were studied. Our results illustrate both the current possibilities and limitations of solution-state NMR for studying membrane proteins, and highlight the benefits of an approach where several membrane mimicking systems and measurements techniques are used in combination to arrive at correct conclusions on the properties of proteins.

Place, publisher, year, edition, pages
Stockholm: Department of Biochemistry and Biophysics, Stockholm University, 2019. p. 85
National Category
Biophysics
Research subject
Biophysics
Identifiers
urn:nbn:se:su:diva-167352 (URN)978-91-7797-692-9 (ISBN)978-91-7797-693-6 (ISBN)
Public defence
2019-05-23, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
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Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 6: Manuscript.

Available from: 2019-04-26 Created: 2019-04-02 Last updated: 2019-04-17Bibliographically approved

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