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Isolation and characterization of the E. coli membrane protein production strain Mutant56(DE3)
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.
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Number of Authors: 112017 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 45089Article in journal (Refereed) Published
Abstract [en]

Membrane protein production is usually toxic to E. coli. However, using genetic screens strains can be isolated in which the toxicity of membrane protein production is reduced, thereby improving production yields. Best known examples are the C41(DE3) and C43(DE3) strains, which are both derived from the T7 RNA polymerase (P)-based BL21(DE3) protein production strain. In C41(DE3) and C43(DE3) mutations lowering t7rnap expression levels result in strongly reduced T7 RNAP accumulation levels. As a consequence membrane protein production stress is alleviated in the C41(DE3) and C43(DE3) strains, thereby increasing membrane protein yields. Here, we isolated Mutant56(DE3) from BL21(DE3) using a genetic screen designed to isolate BL21(DE3)-derived strains with mutations alleviating membrane protein production stress other than the ones in C41(DE3) and C43(DE3). The defining mutation of Mutant56(DE3) changes one amino acid in its T7 RNAP, which weakens the binding of the T7 RNAP to the T7 promoter governing target gene expression rather than lowering T7 RNAP levels. For most membrane proteins tested yields in Mutant56(DE3) were considerably higher than in C41(DE3) and C43(DE3). Thus, the isolation of Mutant56(DE3) shows that the evolution of BL21(DE3) can be promoted towards further enhanced membrane protein production.

Place, publisher, year, edition, pages
2017. Vol. 7, article id 45089
National Category
Biological Sciences Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy)
Research subject
Biochemistry
Identifiers
URN: urn:nbn:se:su:diva-142640DOI: 10.1038/srep45089ISI: 000397309700001OAI: oai:DiVA.org:su-142640DiVA, id: diva2:1095526
Available from: 2017-05-15 Created: 2017-05-15 Last updated: 2018-08-17Bibliographically approved
In thesis
1. Protein production in the E. coli cell envelope
Open this publication in new window or tab >>Protein production in the E. coli cell envelope
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Proteins fulfil essential functions in every cell and malfunctioning proteins are often the cause of diseases. On the other hand, proteins like antibody fragments or hormones can be used to treat diseases. Proteins are often produced in the bacterium Escherichia coli so that they can be studied to understand their (mal)function or so that they can be used to treat a disease. Unfortunately, producing proteins in the cell envelope of E. coli, like integral membrane proteins, which are important drug targets, and secretory proteins like antibody fragments and hormones, often results in unsatisfactory yields. Therefore, the objectives of this doctoral thesis were to identify bottlenecks that can limit the production of recombinant proteins in the cell envelope of E. coli and to try to overcome these bottlenecks. In the first study, we isolated and characterized the E. coli membrane protein production strain Mt56(DE3). This strain, in which the target gene expression intensity is strongly reduced, outcompetes the standard E. coli membrane protein production strains for most targets tested. In the second and third study we focused on the production of secretory proteins, i.e., proteins that are translocated across the inner membrane into the periplasm of E. coli. First, we investigated the impact of the targeting pathway used to direct a secretory protein to the translocation machinery on the cell physiology and protein production yields. We found that the co-translational targeting of a produced protein saturates the capacity of the translocation machinery resulting in heavily impaired biomass formation and low protein production yields. In contrast, post-translational targeting of a produced protein did not saturate the capacity of the protein translocation machinery resulting in hardly affected biomass formation and high protein production yields. In the third study we investigated how optimizing the production of a co-translationally targeted protein, by harmonizing its production rate with the capacity of the protein translocation machinery, affects the physiology of the cell. We found that, in stark contrast to the non-optimized condition, the optimized production did not affect the composition of the E. coli proteome. This surprising finding indicates that a protein can be produced efficiently in the periplasm of E. coli without compromising the physiology of the cell. In the last study we aimed at developing an outer membrane vesicle-based tuberculosis vaccine. To this end, an E. coli strain was created that produced outer membrane vesicles coated with different tuberculosis antigens. It was shown that a homogenous population of vesicles was produced, which will hopefully facilitate the isolation of these vesicles on an industrial scale.

Place, publisher, year, edition, pages
Stockholm: Department of Biochemistry and Biophysics, Stockholm University, 2018. p. 91
Keywords
E. coli, protein biogenesis, recombinant proteins, membrane proteins, secretory proteins, protein displays, outer membrane vesicles
National Category
Biochemistry and Molecular Biology Microbiology
Research subject
Biochemistry
Identifiers
urn:nbn:se:su:diva-158451 (URN)978-91-7797-402-4 (ISBN)978-91-7797-403-1 (ISBN)
Public defence
2018-10-08, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 2: Manuscript.

Available from: 2018-09-13 Created: 2018-08-15 Last updated: 2018-09-04Bibliographically approved

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