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  • 1.
    Baumgarten, Thomas
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Protein production in the E. coli cell envelope2018Doctoral 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.

  • 2.
    Baumgarten, Thomas
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Schlegel, Susan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Wagner, Samuel
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Löw, Mirjam
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Eriksson, Jonas
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Bonde, Ida
    Herrgård, Markus J.
    Heipieper, Hermann J.
    Nørholm, Morten H. H.
    Slotboom, Dirk Jan
    de Gier, Jan-Willem
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Isolation and characterization of the E. coli membrane protein production strain Mutant56(DE3)2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 45089Article in journal (Refereed)
    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.

  • 3.
    Baumgarten, Thomas
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Ytterberg, A. Jimmy
    Zubarev, Roman A.
    de Gier, Jan-Willem
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Optimizing Recombinant Protein Production in the Escherichia coli Periplasm Alleviates Stress2018In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 84, no 12, article id e00270Article in journal (Refereed)
    Abstract [en]

    In Escherichia coli, many recombinant proteins are produced in the periplasm. To direct these proteins to this compartment, they are equipped with an N-terminal signal sequence so that they can traverse the cytoplasmic membrane via the protein-conducting Sec translocon. Recently, using the single-chain variable antibody fragment BL1, we have shown that harmonizing the target gene expression intensity with the Sec translocon capacity can be used to improve the production yields of a recombinant protein in the periplasm. Here, we have studied the consequences of improving the production of BL1 in the periplasm by using a proteomics approach. When the target gene expression intensity is not harmonized with the Sec translocon capacity, the impaired translocation of secretory proteins, protein misfolding/aggregation in the cytoplasm, and an inefficient energy metabolism result in poor growth and low protein production yields. The harmonization of the target gene expression intensity with the Sec translocon capacity results in normal growth, enhanced protein production yields, and, surprisingly, a composition of the proteome that is-besides the produced target-the same as that of cells with an empty expression vector. Thus, the single-chain variable antibody fragment BL1 can be efficiently produced in the periplasm without causing any notable detrimental effects to the production host. Finally, we show that under the optimized conditions, a small fraction of the target protein is released into the extracellular milieu via outer membrane vesicles. We envisage that our observations can be used to design strategies to further improve the production of secretory recombinant proteins in E. coli.

    IMPORTANCE The bacterium Escherichia coli is widely used to produce recombinant proteins. Usually, trial-and-error-based screening approaches are used to identify conditions that lead to high recombinant protein production yields. Here, for the production of an antibody fragment in the periplasm of E. coli, we show that an optimization of its production is accompanied by the alleviation of stress. This indicates that the monitoring of stress responses could be used to facilitate enhanced recombinant protein production yields.

  • 4. Daleke-Schermerhorn, Maria H.
    et al.
    Felix, Tristan
    Soprova, Zora
    ten Hagen-Jongman, Corinne M.
    Vikström, David
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Xbrane Bioscience AB, Sweden.
    Majlessi, Laleh
    Beskers, Joep
    Follmann, Frank
    de Punder, Karin
    van der Wel, Nicole N.
    Baumgarten, Thomas
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Pham, Thang V.
    Piersma, Sander R.
    Jimenez, Connie R.
    van Ulsen, Peter
    de Gier, Jan-Willem
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Leclerc, Claude
    Jong, Wouter S. P.
    Luirink, Joen
    Decoration of Outer Membrane Vesicles with Multiple Antigens by Using an Autotransporter Approach2014In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 80, no 18, p. 5854-5865Article in journal (Refereed)
    Abstract [en]

    Outer membrane vesicles (OMVs) are spherical nanoparticles that naturally shed from Gram-negative bacteria. They are rich in immunostimulatory proteins and lipopolysaccharide but do not replicate, which increases their safety profile and renders them attractive vaccine vectors. By packaging foreign polypeptides in OMVs, specific immune responses can be raised toward heterologous antigens in the context of an intrinsic adjuvant. Antigens exposed at the vesicle surface have been suggested to elicit protection superior to that from antigens concealed inside OMVs, but hitherto robust methods for targeting heterologous proteins to the OMV surface have been lacking. We have exploited our previously developed hemoglobin protease (Hbp) autotransporter platform for display of heterologous polypeptides at the OMV surface. One, two, or three of the Mycobacterium tuberculosis antigens ESAT6, Ag85B, and Rv2660c were targeted to the surface of Escherichia coli OMVs upon fusion to Hbp. Furthermore, a hypervesiculating Delta tolR Delta tolA derivative of attenuated Salmonella enterica serovar Typhimurium SL3261 was generated, enabling efficient release and purification of OMVs decorated with multiple heterologous antigens, exemplified by the M. tuberculosis antigens and epitopes from Chlamydia trachomatis major outer membrane protein (MOMP). Also, we showed that delivery of Salmonella OMVs displaying Ag85B to antigen-presenting cells in vitro results in processing and presentation of an epitope that is functionally recognized by Ag85B-specific T cell hybridomas. In conclusion, the Hbp platform mediates efficient display of (multiple) heterologous antigens, individually or combined within one molecule, at the surface of OMVs. Detection of antigen-specific immune responses upon vesicle-mediated delivery demonstrated the potential of our system for vaccine development.

  • 5. Eberlein, Christian
    et al.
    Baumgarten, Thomas
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Starke, Stephan
    Heipieper, Hermann J.
    Immediate response mechanisms of Gram-negative solvent-tolerant bacteria to cope with environmental stress: cis-trans isomerization of unsaturated fatty acids and outer membrane vesicle secretion2018In: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 102, no 6, p. 2583-2593Article, review/survey (Refereed)
    Abstract [en]

    Bacteria have evolved an array of adaptive mechanisms enabling them to survive and grow in the presence of different environmental stresses. These mechanisms include either modifications of the membrane or changes in the overall energy status, cell morphology, and cell surface properties. Long-term adaptations are dependent on transcriptional regulation, the induction of anabolic pathways, and cell growth. However, to survive sudden environmental changes, bacterial short-term responses are essential to keep the cells alive after the occurrence of an environmental stress factor such as heat shock or the presence of toxic organic solvents. Thus far, two main short-term responses are known. On the one hand, a fast isomerization of cis into trans unsaturated fatty leads to a quick rigidification of the cell membrane, a mechanism known in some genera of Gram-negative bacteria. On the other hand, a fast, effective, and ubiquitously present countermeasure is the release of outer membrane vesicles (OMVs) from the cell surface leading to a rapid increase in cell surface hydrophobicity and finally to the formation of cell aggregates and biofilms. These immediate response mechanisms just allow the bacteria to stay physiologically active and to employ long-term responses to assure viability upon changing environmental conditions. Here, we provide insight into the two aforementioned rapid adaptive mechanisms affecting ultimately the cell envelope of Gram-negative bacteria.

  • 6.
    Hjelm, Anna
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Schlegel, Susan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Baumgarten, Thomas
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Klepsch, Mirjam
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Wickström, David
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Drew, David
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    de Gier, Jan-Willem
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Optimizing E. coli-Based Membrane Protein Production Using Lemo21(DE3) and GFP-Fusions2013In: Membrane Biogenesis: Methods and Protocols / [ed] Doron Rapaport, Johannes M. Herrmann, Totowa, USA: Humana Press, 2013, p. 381-400Chapter in book (Refereed)
    Abstract [en]

    Optimizing the conditions for the overexpression of membrane proteins in E. coli and their subsequent purification is usually a laborious and time-consuming process. Combining the Lemo21(DE3) strain, which conveniently allows to identify the optimal expression intensity of a membrane protein using only one strain, and membrane proteins C-terminally fused to Green Fluorescent Protein (GFP) greatly facilitates the production of high-quality membrane protein material for functional and structural studies.

  • 7.
    Schlegel, Susan
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Hjelm, Anna
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Baumgarten, Thomas
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Vikström, David
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    de Gier, Jan-Willem
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Bacterial-based membrane protein production2014In: Biochimica et Biophysica Acta. Molecular Cell Research, ISSN 0167-4889, E-ISSN 1879-2596, Vol. 1843, no 8, p. 1739-1749Article, review/survey (Refereed)
    Abstract [en]

    Escherichia coli is by far the most widely used bacterial host for the production of membrane proteins. Usually, different strains, culture conditions and production regimes are screened for to design the optimal production process. However, these E. coli-based screening approaches often do not result in satisfactory membrane protein production yields. Recently, it has been shown that (i) E. coli strains with strongly improved membrane protein production characteristics can be engineered or selected for, (ii) many membrane proteins can be efficiently produced in E. coli-based cell-free systems, (iii) bacteria other than E. coli can be used for the efficient production of membrane proteins, and, (iv) membrane protein variants that retain functionality but are produced at higher yields than the wild-type protein can be engineered or selected for. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.

  • 8. Ytterberg, A. Jimmy
    et al.
    Zubarev, Roman A.
    Baumgarten, Thomas
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Post-translational targeting of a recombinant protein promotes its efficient secretion into the E. coli periplasmManuscript (preprint) (Other academic)
  • 9.
    Zhang, Zhe
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Kuipers, Grietje
    Niemiec, Lukasz
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Baumgarten, Thomas
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Slotboom, Dirk Jan
    de Gier, Jan-Willem
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Hjelm, Anna
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    High-level production of membrane proteins in E-coli BL21(DE3) by omitting the inducer IPTG2015In: Microbial Cell Factories, ISSN 1475-2859, E-ISSN 1475-2859, Vol. 14, article id 142Article in journal (Refereed)
    Abstract [en]

    Background: For membrane protein production, the Escherichia coli T7 RNA polymerase (T7 RNAP)-based protein production strain BL21(DE3) in combination with T7-promoter based expression vectors is widely used. Cells are routinely cultured in Lysogeny broth (LB medium) and expression of the chromosomally localized t7rnap gene is governed by the isopropyl-beta-D-1-thiogalactopyranoside (IPTG) inducible lacUV5 promoter. The T7 RNAP drives the expression of the plasmid borne gene encoding the recombinant membrane protein. Production of membrane proteins in the cytoplasmic membrane rather than in inclusion bodies in a misfolded state is usually preferred, but often hampered due to saturation of the capacity of the Sec-translocon, resulting in low yields. Results: Contrary to expectation we observed that omission of IPTG from BL21(DE3) cells cultured in LB medium can lead to significantly higher membrane protein production yields than when IPTG is added. In the complete absence of IPTG cultures stably produce membrane proteins in the cytoplasmic membrane, whereas upon the addition of IPTG membrane proteins aggregate in the cytoplasm and non-producing clones are selected for. Furthermore, in the absence of IPTG, membrane proteins are produced at a lower rate than in the presence of IPTG. These observations indicate that in the absence of IPTG the Sec-translocon capacity is not/hardly saturated, leading to enhanced membrane protein production yields in the cytoplasmic membrane. Importantly, for more than half of the targets tested the yields obtained using un-induced BL21(DE3) cells were higher than the yields obtained in the widely used membrane protein production strains C41(DE3) and C43(DE3). Since most secretory proteins reach the periplasm via the Sec-translocon, we also monitored the production of three secretory recombinant proteins in the periplasm of BL21(DE3) cells in the presence and absence of IPTG. For all three targets tested omitting IPTG led to the highest production levels in the periplasm. Conclusions: Omission of IPTG from BL21(DE3) cells cultured in LB medium provides a very cost-and time effective alternative for the production of membrane and secretory proteins. Therefore, we recommend that this condition is incorporated in membrane- and secretory protein production screens.

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