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Jiang R, Yuan S, Zhou Y, Wei Y, Li F, Wang M, Chen B, Yu H. Strategies to overcome the challenges of low or no expression of heterologous proteins in Escherichia coli. Biotechnol Adv 2024; 75:108417. [PMID: 39038691 DOI: 10.1016/j.biotechadv.2024.108417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Revised: 07/18/2024] [Accepted: 07/19/2024] [Indexed: 07/24/2024]
Abstract
Protein expression is a critical process in diverse biological systems. For Escherichia coli, a widely employed microbial host in industrial catalysis and healthcare, researchers often face significant challenges in constructing recombinant expression systems. To maximize the potential of E. coli expression systems, it is essential to address problems regarding the low or absent production of certain target proteins. This article presents viable solutions to the main factors posing challenges to heterologous protein expression in E. coli, which includes protein toxicity, the intrinsic influence of gene sequences, and mRNA structure. These strategies include specialized approaches for managing toxic protein expression, addressing issues related to mRNA structure and codon bias, advanced codon optimization methodologies that consider multiple factors, and emerging optimization techniques facilitated by big data and machine learning.
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Affiliation(s)
- Ruizhao Jiang
- Department of Chemical Engineering, Tsinghua University, Beijing 100084, China; Key Laboratory of Industrial Biocatalysis (Tsinghua University), the Ministry of Education, Beijing 100084, China
| | - Shuting Yuan
- Department of Chemical Engineering, Tsinghua University, Beijing 100084, China; Key Laboratory of Industrial Biocatalysis (Tsinghua University), the Ministry of Education, Beijing 100084, China
| | - Yilong Zhou
- Tanwei College, Tsinghua University, Beijing 100084, China
| | - Yuwen Wei
- Department of Chemical Engineering, Tsinghua University, Beijing 100084, China; Key Laboratory of Industrial Biocatalysis (Tsinghua University), the Ministry of Education, Beijing 100084, China
| | - Fulong Li
- Beijing Evolyzer Co.,Ltd., 100176, China
| | | | - Bo Chen
- Beijing Evolyzer Co.,Ltd., 100176, China
| | - Huimin Yu
- Department of Chemical Engineering, Tsinghua University, Beijing 100084, China; Key Laboratory of Industrial Biocatalysis (Tsinghua University), the Ministry of Education, Beijing 100084, China; Center for Synthetic and Systems Biology, Tsinghua University, Beijing 100084, China.
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Karyolaimos A, de Gier JW. Strategies to Enhance Periplasmic Recombinant Protein Production Yields in Escherichia coli. Front Bioeng Biotechnol 2021; 9:797334. [PMID: 34970535 PMCID: PMC8712718 DOI: 10.3389/fbioe.2021.797334] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 11/24/2021] [Indexed: 11/29/2022] Open
Abstract
Main reasons to produce recombinant proteins in the periplasm of E. coli rather than in its cytoplasm are to -i- enable disulfide bond formation, -ii- facilitate protein isolation, -iii- control the nature of the N-terminus of the mature protein, and -iv- minimize exposure to cytoplasmic proteases. However, hampered protein targeting, translocation and folding as well as protein instability can all negatively affect periplasmic protein production yields. Strategies to enhance periplasmic protein production yields have focused on harmonizing secretory recombinant protein production rates with the capacity of the secretory apparatus by transcriptional and translational tuning, signal peptide selection and engineering, increasing the targeting, translocation and periplasmic folding capacity of the production host, preventing proteolysis, and, finally, the natural and engineered adaptation of the production host to periplasmic protein production. Here, we discuss these strategies using notable examples as a thread.
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Affiliation(s)
| | - Jan-Willem de Gier
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
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3
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Cautionary Notes on the Use of Arabinose- and Rhamnose-Inducible Expression Vectors in Pseudomonas aeruginosa. J Bacteriol 2021; 203:e0022421. [PMID: 34096777 DOI: 10.1128/jb.00224-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The Pseudomonas aeruginosa virulence factor regulator (Vfr) is a cyclic AMP (cAMP)-responsive transcription factor homologous to the Escherichia coli cAMP receptor protein (CRP). Unlike CRP, which plays a central role in E. coli energy metabolism and catabolite repression, Vfr is primarily involved in the control of P. aeruginosa virulence factor expression. Expression of the Vfr regulon is controlled at the level of vfr transcription, Vfr translation, cAMP synthesis, and cAMP degradation. While investigating mechanisms that regulate Vfr translation, we placed vfr transcription under the control of the rhaBp rhamnose-inducible promoter system (designated PRha) and found that PRha promoter activity was highly dependent upon vfr. Vfr dependence was also observed for the araBp arabinose-inducible promoter (designated PBAD). The observation of Vfr dependence was not entirely unexpected. Both promoters are derived from E. coli, where maximal promoter activity is dependent upon CRP. Like CRP, we found that Vfr directly binds to promoter probes derived from the PRha and PBAD promoters in vitro. Because Vfr-cAMP activity is highly integrated into numerous global regulatory systems, including c-di-GMP signaling, the Gac/Rsm system, MucA/AlgU/AlgZR signaling, and Hfq/sRNAs, the potential exists for significant variability in PRha and PBAD promoter activity in a variety of genetic backgrounds, and use of these promoter systems in P. aeruginosa should be employed with caution. IMPORTANCE Heterologous gene expression and complementation constitute a valuable and widely utilized tool in bacterial genetics. The arabinose-inducible ParaBAD (PBAD) and rhamnose-inducible PrhaBAD (PRha) promoter systems are commonly used in P. aeruginosa genetics and prized for the tight control and dynamic expression ranges that can be achieved. In this study, we demonstrate that the activity of both promoters is dependent upon the cAMP-dependent transcription factor Vfr. While this poses an obvious problem for use in a vfr mutant background, the issue is more pervasive, considering that vfr transcription/synthesis and cAMP homeostasis are highly integrated into the cellular physiology of the organism and influenced by numerous global regulatory systems. Fortunately, the synthetic PTac promoter is not subject to Vfr regulatory control.
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Lozano Terol G, Gallego-Jara J, Sola Martínez RA, Martínez Vivancos A, Cánovas Díaz M, de Diego Puente T. Impact of the Expression System on Recombinant Protein Production in Escherichia coli BL21. Front Microbiol 2021; 12:682001. [PMID: 34234760 PMCID: PMC8257044 DOI: 10.3389/fmicb.2021.682001] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 05/18/2021] [Indexed: 12/13/2022] Open
Abstract
Recombinant protein production for medical, academic, or industrial applications is essential for our current life. Recombinant proteins are obtained mainly through microbial fermentation, with Escherichia coli being the host most used. In spite of that, some problems are associated with the production of recombinant proteins in E. coli, such as the formation of inclusion bodies, the metabolic burden, or the inefficient translocation/transport system of expressed proteins. Optimizing transcription of heterologous genes is essential to avoid these drawbacks and develop competitive biotechnological processes. Here, expression of YFP reporter protein is evaluated under the control of four promoters of different strength (PT7lac, Ptrc, Ptac, and PBAD) and two different replication origins (high copy number pMB1′ and low copy number p15A). In addition, the study has been carried out with the E. coli BL21 wt and the ackA mutant strain growing in a rich medium with glucose or glycerol as carbon sources. Results showed that metabolic burden associated with transcription and translation of foreign genes involves a decrease in recombinant protein expression. It is necessary to find a balance between plasmid copy number and promoter strength to maximize soluble recombinant protein expression. The results obtained represent an important advance on the most suitable expression system to improve both the quantity and quality of recombinant proteins in bioproduction engineering.
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Affiliation(s)
- Gema Lozano Terol
- Department of Biochemistry and Molecular Biology and Immunology (B), Faculty of Chemistry, University of Murcia, Campus of Espinardo, Regional Campus of International Excellence "Campus Mare Nostrum", Murcia, Spain
| | - Julia Gallego-Jara
- Department of Biochemistry and Molecular Biology and Immunology (B), Faculty of Chemistry, University of Murcia, Campus of Espinardo, Regional Campus of International Excellence "Campus Mare Nostrum", Murcia, Spain
| | - Rosa Alba Sola Martínez
- Department of Biochemistry and Molecular Biology and Immunology (B), Faculty of Chemistry, University of Murcia, Campus of Espinardo, Regional Campus of International Excellence "Campus Mare Nostrum", Murcia, Spain
| | - Adrián Martínez Vivancos
- Department of Biochemistry and Molecular Biology and Immunology (B), Faculty of Chemistry, University of Murcia, Campus of Espinardo, Regional Campus of International Excellence "Campus Mare Nostrum", Murcia, Spain
| | - Manuel Cánovas Díaz
- Department of Biochemistry and Molecular Biology and Immunology (B), Faculty of Chemistry, University of Murcia, Campus of Espinardo, Regional Campus of International Excellence "Campus Mare Nostrum", Murcia, Spain
| | - Teresa de Diego Puente
- Department of Biochemistry and Molecular Biology and Immunology (B), Faculty of Chemistry, University of Murcia, Campus of Espinardo, Regional Campus of International Excellence "Campus Mare Nostrum", Murcia, Spain
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Stargardt P, Striedner G, Mairhofer J. Tunable expression rate control of a growth-decoupled T7 expression system by L-arabinose only. Microb Cell Fact 2021; 20:27. [PMID: 33522916 PMCID: PMC7852362 DOI: 10.1186/s12934-021-01512-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 01/07/2021] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Precise regulation of gene expression is of utmost importance for the production of complex membrane proteins (MP), enzymes or other proteins toxic to the host cell. In this article we show that genes under control of a normally Isopropyl β-D-1-thiogalactopyranoside (IPTG)-inducible PT7-lacO promoter can be induced solely with L-arabinose in a newly constructed Escherichia coli expression host BL21-AI<gp2>, a strain based on the recently published approach of bacteriophage inspired growth-decoupled recombinant protein production. RESULTS Here, we show that BL21-AI<gp2> is able to precisely regulate protein production rates on a cellular level in an L-arabinose concentration-dependent manner and simultaneously allows for reallocation of metabolic resources due to L-arabinose induced growth decoupling by the phage derived inhibitor peptide Gp2. We have successfully characterized the system under relevant fed-batch like conditions in microscale cultivation (800 µL) and generated data proofing a relevant increase in specific yields for 6 different Escherichia coli derived MP-GFP fusion proteins by using online-GFP signals, FACS analysis, SDS-PAGE and western blotting. CONCLUSIONS In all cases tested, BL21-AI<gp2> outperformed the parental strain BL21-AI, operated in growth-associated production mode. Specific MP-GFP fusion proteins yields have been improved up to 2.7-fold. Therefore, this approach allows for fine tuning of MP production or expression of multi-enzyme pathways where e.g. particular stoichiometries have to be met to optimize product flux.
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Affiliation(s)
| | - Gerald Striedner
- Department of Biotechnology, University of Natural Resources and Life Sciences (BOKU), Muthgasse 18, 1190, Vienna, Austria
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Laughery MF, Brown AJ, Bohm KA, Sivapragasam S, Morris HS, Tchmola M, Washington AD, Mitchell D, Mather S, Malc EP, Mieczkowski PA, Roberts SA, Wyrick JJ. Atypical UV Photoproducts Induce Non-canonical Mutation Classes Associated with Driver Mutations in Melanoma. Cell Rep 2020; 33:108401. [PMID: 33207206 PMCID: PMC7709870 DOI: 10.1016/j.celrep.2020.108401] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 09/28/2020] [Accepted: 10/27/2020] [Indexed: 12/13/2022] Open
Abstract
Somatic mutations in skin cancers and other ultraviolet (UV)-exposed cells are typified by C>T and CC>TT substitutions at dipyrimidine sequences; however, many oncogenic “driver” mutations in melanoma do not fit this UV signature. Here, we use genome sequencing to characterize mutations in yeast repeatedly irradiated with UV light. Analysis of ~50,000 UV-induced mutations reveals abundant non-canonical mutations, including T>C, T>A, and AC>TT substitutions. These mutations display transcriptional asymmetry that is modulated by nucleotide excision repair (NER), indicating that they are caused by UV photoproducts. Using a sequencing method called UV DNA endonuclease sequencing (UVDE-seq), we confirm the existence of an atypical thymine-adenine photoproduct likely responsible for UV-induced T>A substitutions. Similar non-canonical mutations are present in skin cancers, which also display transcriptional asymmetry and dependence on NER. These include multiple driver mutations, most prominently the recurrent BRAF V600E and V600K substitutions, suggesting that mutations arising from rare, atypical UV photoproducts may play a role in melanomagenesis. UV mutagenesis has been well studied, but many driver mutations in melanoma do not fit the canonical UV signature. Using whole-genome sequencing, Laughery et al. show that UV induces a broader spectrum of mutations than anticipated. Non-canonical UV mutations are likely caused by atypical photoproducts, which may contribute to melanomagenesis.
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Affiliation(s)
- Marian F Laughery
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
| | - Alexander J Brown
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
| | - Kaitlynne A Bohm
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
| | - Smitha Sivapragasam
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
| | - Haley S Morris
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
| | - Mila Tchmola
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
| | - Angelica D Washington
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
| | - Debra Mitchell
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
| | - Stephen Mather
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
| | - Ewa P Malc
- Department of Genetics, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Piotr A Mieczkowski
- Department of Genetics, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Steven A Roberts
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA; Center for Reproductive Biology, Washington State University, Pullman, WA 99164, USA.
| | - John J Wyrick
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA; Center for Reproductive Biology, Washington State University, Pullman, WA 99164, USA.
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Schuller A, Cserjan-Puschmann M, Tauer C, Jarmer J, Wagenknecht M, Reinisch D, Grabherr R, Striedner G. Escherichia coli σ 70 promoters allow expression rate control at the cellular level in genome-integrated expression systems. Microb Cell Fact 2020; 19:58. [PMID: 32138729 PMCID: PMC7059391 DOI: 10.1186/s12934-020-01311-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 02/17/2020] [Indexed: 12/18/2022] Open
Abstract
Background The genome-integrated T7 expression system offers significant advantages, in terms of productivity and product quality, even when expressing the gene of interest (GOI) from a single copy. Compared to plasmid-based expression systems, this system does not incur a plasmid-mediated metabolic load, and it does not vary the dosage of the GOI during the production process. However, long-term production with T7 expression system leads to a rapidly growing non-producing population, because the T7 RNA polymerase (RNAP) is prone to mutations. The present study aimed to investigate whether two σ70 promoters, which were recognized by the Escherichia coli host RNAP, might be suitable in genome-integrated expression systems. We applied a promoter engineering strategy that allowed control of expressing the model protein, GFP, by introducing lac operators (lacO) into the constitutive T5 and A1 promoter sequences. Results We showed that, in genome-integrated E. coli expression systems that used σ70 promoters, the number of lacO sites must be well balanced. Promoters containing three and two lacO sites exhibited low basal expression, but resulted in a complete stop in recombinant protein production in partially induced cultures. In contrast, expression systems regulated by a single lacO site and the lac repressor element, lacIQ, on the same chromosome caused very low basal expression, were highly efficient in recombinant protein production, and enables fine-tuning of gene expression levels on a cellular level. Conclusions Based on our results, we hypothesized that this phenomenon was associated with the autoregulation of the lac repressor protein, LacI. We reasoned that the affinity of LacI for the lacO sites of the GOI must be lower than the affinity of LacI to the lacO sites of the endogenous lac operon; otherwise, LacI autoregulation could not take place, and the lack of LacI autoregulation would lead to a disturbance in lac repressor-mediated regulation of transcription. By exploiting the mechanism of LacI autoregulation, we created a novel E. coli expression system for use in recombinant protein production, synthetic biology, and metabolic engineering applications.
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Affiliation(s)
- Artur Schuller
- Christian Doppler Laboratory for Production of Next-level Biopharmaceuticals in E. coli, Department of Biotechnology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190, Vienna, Austria
| | - Monika Cserjan-Puschmann
- Christian Doppler Laboratory for Production of Next-level Biopharmaceuticals in E. coli, Department of Biotechnology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190, Vienna, Austria.
| | - Christopher Tauer
- Christian Doppler Laboratory for Production of Next-level Biopharmaceuticals in E. coli, Department of Biotechnology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190, Vienna, Austria
| | - Johanna Jarmer
- Boehringer Ingelheim RCV GmbH & Co KG, Dr.-Boehringer-Gasse 5-11, 1120, Vienna, Austria
| | - Martin Wagenknecht
- Boehringer Ingelheim RCV GmbH & Co KG, Dr.-Boehringer-Gasse 5-11, 1120, Vienna, Austria
| | - Daniela Reinisch
- Boehringer Ingelheim RCV GmbH & Co KG, Dr.-Boehringer-Gasse 5-11, 1120, Vienna, Austria
| | - Reingard Grabherr
- Christian Doppler Laboratory for Production of Next-level Biopharmaceuticals in E. coli, Department of Biotechnology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190, Vienna, Austria
| | - Gerald Striedner
- Christian Doppler Laboratory for Production of Next-level Biopharmaceuticals in E. coli, Department of Biotechnology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190, Vienna, Austria
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Karyolaimos A, Ampah-Korsah H, Zhang Z, de Gier JW. Shaping Escherichia coli for recombinant membrane protein production. FEMS Microbiol Lett 2018; 365:5040224. [DOI: 10.1093/femsle/fny152] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Accepted: 06/18/2018] [Indexed: 12/29/2022] Open
Affiliation(s)
- Alexandros Karyolaimos
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Sv. Arrheniusväg 16C, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Henry Ampah-Korsah
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Sv. Arrheniusväg 16C, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Zhe Zhang
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Sv. Arrheniusväg 16C, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Jan-Willem de Gier
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Sv. Arrheniusväg 16C, Stockholm University, SE-106 91, Stockholm, Sweden
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9
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Optimizing Recombinant Protein Production in the Escherichia coli Periplasm Alleviates Stress. Appl Environ Microbiol 2018; 84:AEM.00270-18. [PMID: 29654183 DOI: 10.1128/aem.00270-18] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 04/08/2018] [Indexed: 11/20/2022] Open
Abstract
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. coliIMPORTANCE 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.
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Małachowska A, Olszewski P. TECS: a toxin expression control strategy as a tool for optimization of inducible promoters. Microb Cell Fact 2018. [PMID: 29534758 PMCID: PMC5851080 DOI: 10.1186/s12934-018-0891-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Background Transcriptional control of gene expression is a widely utilized regulatory mechanism in synthetic biology, biotechnology and recombinant protein production. It is achieved by utilization of naturally occurring promoters responding to nutrients or chemicals. Despite their regulatory properties, these promoters often possess features which diminish their utility for biotechnology. High basal expression level and low induction ratio can be removed using genetic engineering techniques, although this process is often laborious and time-consuming. Results In order to facilitate optimization process for inducible promoters, we developed a simple method based on a conditional toxin expression which we abbreviate as toxin expression control strategy (TECS). In the presence of sucrose, SacB enzyme from Bacillus subtilis synthesizes levans which cause Eschericha coli cell lysis. However, in the absence of sucrose the enzyme does not affect the growth of the host. We utilized this feature to develop a two-step protocol allowing for efficient selection of inducible promoter variants. Using TECS we were able to modify the well-described pBAD promoter to decrease its leakage while maintaining high activity upon induction. Furthermore, we used the method to test transcriptional interference of lambda phage-derived sequence and optimize it for higher induction levels through random mutagenesis. Conclusions We show that TECS is an efficient tool for optimization and development of inducible promoter systems in E. coli. Our strategy is very effective in the selection of promoter variants with improved properties. Its simplicity and short hands-on time make it an attractive method to optimize existing promoters and to construct novel, engineered genetic elements which improve properties of an inducible promoter system. Electronic supplementary material The online version of this article (10.1186/s12934-018-0891-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Aleksandra Małachowska
- Department of Genetics and Biosystematics, University of Gdańsk, ul. Wita Stwosza 59, 80-308, Gdańsk, Poland
| | - Paweł Olszewski
- Department of Genetics and Biosystematics, University of Gdańsk, ul. Wita Stwosza 59, 80-308, Gdańsk, Poland.
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11
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Kaur J, Kumar A, Kaur J. Strategies for optimization of heterologous protein expression in E. coli: Roadblocks and reinforcements. Int J Biol Macromol 2018; 106:803-822. [DOI: 10.1016/j.ijbiomac.2017.08.080] [Citation(s) in RCA: 126] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2017] [Revised: 08/02/2017] [Accepted: 08/12/2017] [Indexed: 12/29/2022]
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12
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Kaur J, Kumar A, Kaur J. Strategies for optimization of heterologous protein expression in E. coli: Roadblocks and reinforcements. Int J Biol Macromol 2018. [DOI: 10.1016/j.ijbiomac.2017.08.080 10.1242/jeb.069716] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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13
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Kuipers G, Karyolaimos A, Zhang Z, Ismail N, Trinco G, Vikström D, Slotboom DJ, de Gier JW. The tunable pReX expression vector enables optimizing the T7-based production of membrane and secretory proteins in E. coli. Microb Cell Fact 2017; 16:226. [PMID: 29246156 PMCID: PMC5732464 DOI: 10.1186/s12934-017-0840-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 12/05/2017] [Indexed: 11/16/2022] Open
Abstract
Background To optimize the production of membrane and secretory proteins in Escherichia coli, it is critical to harmonize the expression rates of the genes encoding these proteins with the capacity of their biogenesis machineries. Therefore, we engineered the Lemo21(DE3) strain, which is derived from the T7 RNA polymerase-based BL21(DE3) protein production strain. In Lemo21(DE3), the T7 RNA polymerase activity can be modulated by the controlled co-production of its natural inhibitor T7 lysozyme. This setup enables to precisely tune target gene expression rates in Lemo21(DE3). The t7lys gene is expressed from the pLemo plasmid using the titratable rhamnose promoter. A disadvantage of the Lemo21(DE3) setup is that the system is based on two plasmids, a T7 expression vector and pLemo. The aim of this study was to simplify the Lemo21(DE3) setup by incorporating the key elements of pLemo in a standard T7-based expression vector. Results By incorporating the gene encoding the T7 lysozyme under control of the rhamnose promoter in a standard T7-based expression vector, pReX was created (ReX stands for Regulated gene eXpression). For two model membrane proteins and a model secretory protein we show that the optimized production yields obtained with the pReX expression vector in BL21(DE3) are similar to the ones obtained with Lemo21(DE3) using a standard T7 expression vector. For another secretory protein, a c-type cytochrome, we show that pReX, in contrast to Lemo21(DE3), enables the use of a helper plasmid that is required for the maturation and hence the production of this heme c protein. Conclusions Here, we created pReX, a T7-based expression vector that contains the gene encoding the T7 lysozyme under control of the rhamnose promoter. pReX enables regulated T7-based target gene expression using only one plasmid. We show that with pReX the production of membrane and secretory proteins can be readily optimized. Importantly, pReX facilitates the use of helper plasmids. Furthermore, the use of pReX is not restricted to BL21(DE3), but it can in principle be used in any T7 RNAP-based strain. Thus, pReX is a versatile alternative to Lemo21(DE3). Electronic supplementary material The online version of this article (10.1186/s12934-017-0840-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Grietje Kuipers
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91, Stockholm, Sweden.,Xbrane Biopharma AB, SE-111 45, Stockholm, Sweden
| | - Alexandros Karyolaimos
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Zhe Zhang
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91, Stockholm, Sweden
| | | | - Gianluca Trinco
- University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute, NL-9747 AG, Groningen, The Netherlands
| | | | - Dirk Jan Slotboom
- University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute, NL-9747 AG, Groningen, The Netherlands
| | - Jan-Willem de Gier
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91, Stockholm, Sweden.
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14
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Hook-Barnard IG, Hinton DM. Transcription Initiation by Mix and Match Elements: Flexibility for Polymerase Binding to Bacterial Promoters. GENE REGULATION AND SYSTEMS BIOLOGY 2017. [DOI: 10.1177/117762500700100020] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Bacterial RNA polymerase is composed of a core of subunits (β β′, α1, α2, ω), which have RNA synthesizing activity, and a specificity factor (σ), which identifies the start of transcription by recognizing and binding to sequence elements within promoter DNA. Four core promoter consensus sequences, the –10 element, the extended –10 (TGn) element, the –35 element, and the UP elements, have been known for many years; the importance of a nontemplate G at position -5 has been recognized more recently. However, the functions of these elements are not the same. The AT-rich UP elements, the –35 elements (–35TTGACA–30), and the extended –10 (15TGn–13) are recognized as double-stranded binding elements, whereas the –5 nontemplate G is recognized in the context of single-stranded DNA at the transcription bubble. Furthermore, the –10 element (–12TATAAT–7) is recognized as both double-stranded DNA for the T:A bp at position –12 and as nontemplate, single-stranded DNA from positions –11 to –7. The single-stranded sequences at positions –11 to –7 as well as the –5 contribute to later steps in transcription initiation that involve isomerization of polymerase and separation of the promoter DNA around the transcription start site. Recent work has demonstrated that the double-stranded elements may be used in various combinations to yield an effective promoter. Thus, while some minimal number of contacts is required for promoter function, polymerase allows the elements to be mixed and matched. Interestingly, which particular elements are used does not appear to fundamentally alter the transcription bubble generated in the stable complex. In this review, we discuss the multiple steps involved in forming a transcriptionally competent polymerase/promoter complex, and we examine what is known about polymerase recognition of core promoter elements. We suggest that considering promoter elements according to their involvement in early (polymerase binding) or later (polymerase isomerization) steps in transcription initiation rather than simply from their match to conventional promoter consensus sequences is a more instructive form of promoter classification.
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Affiliation(s)
- India G. Hook-Barnard
- Gene Expression and Regulation Section, Laboratory of Molecular and Cellular Biology, National Institute of Diabetes Digestive and Kidney Diseases, National Institutes of Health, Bldg. 8 Room 2A-13, Bethesda, MD 20892-0830
| | - Deborah M. Hinton
- Gene Expression and Regulation Section, Laboratory of Molecular and Cellular Biology, National Institute of Diabetes Digestive and Kidney Diseases, National Institutes of Health, Bldg. 8 Room 2A-13, Bethesda, MD 20892-0830
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15
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Baumgarten T, Schlegel S, Wagner S, Löw M, Eriksson J, Bonde I, Herrgård MJ, Heipieper HJ, Nørholm MHH, Slotboom DJ, de Gier JW. Isolation and characterization of the E. coli membrane protein production strain Mutant56(DE3). Sci Rep 2017; 7:45089. [PMID: 28338018 PMCID: PMC5364489 DOI: 10.1038/srep45089] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 02/20/2017] [Indexed: 11/09/2022] Open
Abstract
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.
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Affiliation(s)
- Thomas Baumgarten
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, Stockholm, SE-106 91, Sweden
| | - Susan Schlegel
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, Stockholm, SE-106 91, Sweden
| | - Samuel Wagner
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, Stockholm, SE-106 91, Sweden
| | - Mirjam Löw
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, Stockholm, SE-106 91, Sweden
| | - Jonas Eriksson
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, Stockholm, SE-106 91, Sweden
| | - Ida Bonde
- Technical University of Denmark, Novo Nordisk Foundation Center for Biosustainability, Kogle Alle 6, Hørsholm, 2970, Denmark
| | - Markus J Herrgård
- Technical University of Denmark, Novo Nordisk Foundation Center for Biosustainability, Kogle Alle 6, Hørsholm, 2970, Denmark
| | - Hermann J Heipieper
- Helmholtz Centre for Environmental Research-UFZ, Department of Environmental Biotechnology, Permoserstrasse 15, Leipzig, 04318, Germany
| | - Morten H H Nørholm
- Technical University of Denmark, Novo Nordisk Foundation Center for Biosustainability, Kogle Alle 6, Hørsholm, 2970, Denmark
| | - Dirk Jan Slotboom
- Groningen Biomolecular Science and Biotechnology Institute, University of Groningen, Nijenborgh 4, Groningen, AG, 9747, The Netherlands
| | - Jan-Willem de Gier
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, Stockholm, SE-106 91, Sweden
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16
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The Escherichia coli rhaSR-PrhaBAD Inducible Promoter System Allows Tightly Controlled Gene Expression over a Wide Range in Pseudomonas aeruginosa. Appl Environ Microbiol 2016; 82:6715-6727. [PMID: 27613678 DOI: 10.1128/aem.02041-16] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 09/01/2016] [Indexed: 12/31/2022] Open
Abstract
The araC-ParaBAD inducible promoter system is tightly controlled and allows gene expression to be modulated over a wide range in Escherichia coli, which has led to its widespread use in other bacteria. Although anecdotal evidence suggests that araC-ParaBAD is leaky in Pseudomonas aeruginosa, neither a thorough analysis of this inducible promoter system in P. aeruginosa nor a concerted effort to identify alternatives with improved functionality has been reported. Here, we evaluated the functionality of the araC-ParaBAD system in P. aeruginosa Using transcriptional fusions to a lacZ reporter gene, we determined that the noninduced expression from araC-ParaBAD is high and cannot be reduced by carbon catabolite repression as it can in E. coli Modulating translational initiation by altering ribosome-binding site strength reduced the noninduced activity but also decreased the maximal induced activity and narrowed the induction range. Integrating the inducible promoter system into the posttranscriptional regulatory network that controls catabolite repression in P. aeruginosa significantly decreased the noninduced activity and increased the induction range. In addition to these improvements in the functionality of the araC-ParaBAD system, we found that the lacIq-Ptac and rhaSR-PrhaBAD inducible promoter systems had significantly lower noninduced expression and were inducible over a broader range than araC-ParaBAD We demonstrated that noninduced expression from the araC-ParaBAD system supported the function of genes involved in antibiotic resistance and tryptophan biosynthesis in P. aeruginosa, problems that were avoided with rhaSR-PrhaBAD. rhaSR-PrhaBAD is tightly controlled, allows gene expression over a wide range, and represents a significant improvement over araC-ParaBAD in P. aeruginosa IMPORTANCE: We report the shortcomings of the commonly used Escherichia coli araC-ParaBAD inducible promoter system in Pseudomonas aeruginosa, successfully reengineered it to improve its functionality, and show that the E. coli rhaSR-PrhaBAD system is tightly controlled and allows inducible gene expression over a wide range in P. aeruginosa.
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17
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Schlegel S, Genevaux P, de Gier JW. Isolating Escherichia coli strains for recombinant protein production. Cell Mol Life Sci 2016; 74:891-908. [PMID: 27730255 PMCID: PMC5306230 DOI: 10.1007/s00018-016-2371-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 08/22/2016] [Accepted: 09/16/2016] [Indexed: 12/14/2022]
Abstract
Escherichia coli has been widely used for the production of recombinant proteins. To improve protein production yields in E. coli, directed engineering approaches have been commonly used. However, there are only few reported examples of the isolation of E. coli protein production strains using evolutionary approaches. Here, we first give an introduction to bacterial evolution and mutagenesis to set the stage for discussing how so far selection- and screening-based approaches have been used to isolate E. coli protein production strains. Finally, we discuss how evolutionary approaches may be used in the future to isolate E. coli strains with improved protein production characteristics.
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Affiliation(s)
- Susan Schlegel
- Department of Environmental Systems Science, ETH Zürich, 8092, Zürich, Switzerland
| | - Pierre Genevaux
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Jan-Willem de Gier
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrheniusväg 16C, 106 91, Stockholm, Sweden.
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18
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Valle A, Hervis Y, Socas L, Canet L, Faheem M, Barbosa J, Lanio M, Pazos I. The multigene families of actinoporins (part II): Strategies for heterologous production in Escherichia coli. Toxicon 2016; 118:64-81. [DOI: 10.1016/j.toxicon.2016.03.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 03/24/2016] [Indexed: 11/26/2022]
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19
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Zhang Z, Kuipers G, Niemiec Ł, Baumgarten T, Slotboom DJ, de Gier JW, Hjelm A. High-level production of membrane proteins in E. coli BL21(DE3) by omitting the inducer IPTG. Microb Cell Fact 2015; 14:142. [PMID: 26377812 PMCID: PMC4574001 DOI: 10.1186/s12934-015-0328-z] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 08/28/2015] [Indexed: 11/17/2022] Open
Abstract
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-β-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. Electronic supplementary material The online version of this article (doi:10.1186/s12934-015-0328-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Zhe Zhang
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, 106 91, Stockholm, Sweden.
| | | | - Łukasz Niemiec
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, 106 91, Stockholm, Sweden.
| | - Thomas Baumgarten
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, 106 91, Stockholm, Sweden.
| | - Dirk Jan Slotboom
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands.
| | - Jan-Willem de Gier
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, 106 91, Stockholm, Sweden.
| | - Anna Hjelm
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, 106 91, Stockholm, Sweden.
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20
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De-convoluting the Genetic Adaptations of E. coli C41(DE3) in Real Time Reveals How Alleviating Protein Production Stress Improves Yields. Cell Rep 2015; 10:1758-1766. [DOI: 10.1016/j.celrep.2015.02.029] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 01/29/2015] [Accepted: 02/08/2015] [Indexed: 11/20/2022] Open
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21
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Jajesniak P, Seng Wong T. From genetic circuits to industrial-scale biomanufacturing: bacterial promoters as a cornerstone of biotechnology. AIMS BIOENGINEERING 2015. [DOI: 10.3934/bioeng.2015.3.277] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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22
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Rosano GL, Ceccarelli EA. Recombinant protein expression in Escherichia coli: advances and challenges. Front Microbiol 2014; 5:172. [PMID: 24860555 PMCID: PMC4029002 DOI: 10.3389/fmicb.2014.00172] [Citation(s) in RCA: 1299] [Impact Index Per Article: 129.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 03/29/2014] [Indexed: 12/28/2022] Open
Abstract
Escherichia coli is one of the organisms of choice for the production of recombinant proteins. Its use as a cell factory is well-established and it has become the most popular expression platform. For this reason, there are many molecular tools and protocols at hand for the high-level production of heterologous proteins, such as a vast catalog of expression plasmids, a great number of engineered strains and many cultivation strategies. We review the different approaches for the synthesis of recombinant proteins in E. coli and discuss recent progress in this ever-growing field.
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Affiliation(s)
- Germán L Rosano
- Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas Rosario, Argentina ; Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario Rosario, Argentina
| | - Eduardo A Ceccarelli
- Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas Rosario, Argentina ; Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario Rosario, Argentina
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23
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Coordination of bacterial proteome with metabolism by cyclic AMP signalling. Nature 2013; 500:301-6. [PMID: 23925119 DOI: 10.1038/nature12446] [Citation(s) in RCA: 269] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Accepted: 07/11/2013] [Indexed: 11/08/2022]
Abstract
The cyclic AMP (cAMP)-dependent catabolite repression effect in Escherichia coli is among the most intensely studied regulatory processes in biology. However, the physiological function(s) of cAMP signalling and its molecular triggers remain elusive. Here we use a quantitative physiological approach to show that cAMP signalling tightly coordinates the expression of catabolic proteins with biosynthetic and ribosomal proteins, in accordance with the cellular metabolic needs during exponential growth. The expression of carbon catabolic genes increased linearly with decreasing growth rates upon limitation of carbon influx, but decreased linearly with decreasing growth rate upon limitation of nitrogen or sulphur influx. In contrast, the expression of biosynthetic genes showed the opposite linear growth-rate dependence as the catabolic genes. A coarse-grained mathematical model provides a quantitative framework for understanding and predicting gene expression responses to catabolic and anabolic limitations. A scheme of integral feedback control featuring the inhibition of cAMP signalling by metabolic precursors is proposed and validated. These results reveal a key physiological role of cAMP-dependent catabolite repression: to ensure that proteomic resources are spent on distinct metabolic sectors as needed in different nutrient environments. Our findings underscore the power of quantitative physiology in unravelling the underlying functions of complex molecular signalling networks.
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24
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Apostolaki A, Kalosakas G. Targets of DNA-binding proteins in bacterial promoter regions present enhanced probabilities for spontaneous thermal openings. Phys Biol 2011; 8:026006. [DOI: 10.1088/1478-3975/8/2/026006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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25
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Warnes A, Stephenson JR, Fooks AR, Melling J, Brown MR. Expression of recombinant protein A from the lac promoter in Escherichia coli JM83 is not subject to catabolite repression when grown under specific conditions of continuous culture. Biotechnol Bioeng 2009; 38:1050-8. [PMID: 18600870 DOI: 10.1002/bit.260380914] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Although widely used in experimental and industrial situations, genetically engineered plasmids containing the lac promoter from Escherichia coli are subject to catabolite repression when grown in glucose-containing media. Several methods of overcoming this problem have been investigated by studying the expression of the protein A gene from Staphylococcus aureus under the control of the Escherichia coli lac promoter. When glycerol is used as a sole carbon source, the plasmid is unstable and is rapidly lost from the culture. When the bacteria are grown in chemostats under glucose limitation, the plasmid is maintained, even at high dilution rates, and the expression of protein A is similar to that observed when glycerol was used. The balance between metabolic load and protein A expression seems to be maintained by reducing the gene dose to a tolerable level. Depending on the metabolic conditions prevailing in the culture, this is achieved, either by reducing the copy number of the plasmid or in extreme cases by removing the plasmid altogether.
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Affiliation(s)
- A Warnes
- Division of Biologics, CAMR, Portion Down, Salisbury, SP4 0JG, United Kingdom
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26
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Pyruvate kinase-deficient Escherichia coli exhibits increased plasmid copy number and cyclic AMP levels. J Bacteriol 2009; 191:3041-9. [PMID: 19251844 DOI: 10.1128/jb.01422-08] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previously established consequences of abolishing pyruvate kinase (Pyk) activity in Escherichia coli during aerobic growth on glucose include reduced acetate production, elevated hexose monophosphate (HMP) pathway flux, elevated phosphoenolpyruvate carboxylase (Ppc) flux, and an increased ratio of phosphoenolpyruvate (PEP) to pyruvate. These traits inspired two hypotheses. First, the mutant (PB25) may maintain more plasmid than the wild type (JM101) by combining traits reported to facilitate plasmid DNA synthesis (i.e., decreased Pyk flux and increased HMP pathway and Ppc fluxes). Second, PB25 likely possesses a higher level of cyclic AMP (cAMP) than JM101. This is based on reports that connect elevated PEP/pyruvate ratios to phosphotransferase system signaling and adenylate cyclase activation. To test the first hypothesis, the strains were transformed with a pUC-based, high-copy-number plasmid (pGFPuv), and copy numbers were measured. PB25 exhibited a fourfold-higher copy number than JM101 when grown at 37 degrees C. At 42 degrees C, its plasmid content was ninefold higher than JM101 at 37 degrees C. To test the second hypothesis, cAMP was measured, and the results confirmed it to be higher in PB25 than JM101. This elevation was not enough to elicit a strong regulatory effect, however, as indicated by the comparative expression of the pGFPuv-based reporter gene, gfp(uv), under the control of the cAMP-responsive lac promoter. The elevated cAMP in PB25 suggests that Pyk may participate in glucose catabolite repression by serving among all of the factors that tighten gene expression.
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27
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Is there any role for cAMP-CRP in carbon catabolite repression of the Escherichia coli lac operon? Nat Rev Microbiol 2008; 6:954; author reply 954. [PMID: 18955986 DOI: 10.1038/nrmicro1932-c1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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28
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Abstract
A simple generic method for optimizing membrane protein overexpression in Escherichia coli is still lacking. We have studied the physiological response of the widely used "Walker strains" C41(DE3) and C43(DE3), which are derived from BL21(DE3), to membrane protein overexpression. For unknown reasons, overexpression of many membrane proteins in these strains is hardly toxic, often resulting in high overexpression yields. By using a combination of physiological, proteomic, and genetic techniques we have shown that mutations in the lacUV5 promoter governing expression of T7 RNA polymerase are key to the improved membrane protein overexpression characteristics of the Walker strains. Based on this observation, we have engineered a derivative strain of E. coli BL21(DE3), termed Lemo21(DE3), in which the activity of the T7 RNA polymerase can be precisely controlled by its natural inhibitor T7 lysozyme (T7Lys). Lemo21(DE3) is tunable for membrane protein overexpression and conveniently allows optimizing overexpression of any given membrane protein by using only a single strain rather than a multitude of different strains. The generality and simplicity of our approach make it ideal for high-throughput applications.
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29
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30
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Uc-Mass A, Khodursky A, Brown L, Gottesman ME. Overexpression of phage HK022 Nun protein is toxic for Escherichia coli. J Mol Biol 2008; 380:812-9. [PMID: 18571198 DOI: 10.1016/j.jmb.2008.05.030] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2008] [Revised: 05/01/2008] [Accepted: 05/08/2008] [Indexed: 10/22/2022]
Abstract
The Nun protein of coliphage HK022 excludes superinfecting lambda phage. Nun recognizes and binds to the N utilization (nut) sites on phage lambda nascent RNA and induces transcription termination. Overexpression of Nun from a high-copy plasmid is toxic for Escherichia coli, despite the fact that nut sites are not encoded in the E. coli genome. Cells expressing Nun cannot exit stationary phase. Toxicity is related to transcription termination, since host and nun mutations that block termination also suppress cell killing. Nun inhibits expression of wild-type lacZ, but not lacZ expressed from the Crp/cAMP-independent lacUV5 promoter. Microarray and proteomic analyses show that Nun down-regulates crp and tnaA. Crp overexpression and high indole concentrations partially reverse Nun-mediated toxicity and restore lacZ expression.
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Affiliation(s)
- Augusto Uc-Mass
- Institute of Cancer Research, Columbia University Medical Center, New York, NY 10032, USA
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31
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Transcription initiation by mix and match elements: flexibility for polymerase binding to bacterial promoters. GENE REGULATION AND SYSTEMS BIOLOGY 2007; 1:275-93. [PMID: 19119427 PMCID: PMC2613000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Bacterial RNA polymerase is composed of a core of subunits (beta, beta', alpha1, alpha2, omega), which have RNA synthesizing activity, and a specificity factor (sigma), which identifies the start of transcription by recognizing and binding to sequences elements within promoter DNA. Four core promoter consensus sequences, the -10 element, the extended -10 (TGn) element, the -35 element, and the UP elements, have been known for many years; the importance of a nontemplate G at position -5 has been recognized more recently. However, the functions of these elements are not the same. The AT-rich UP elements, the -35 elements ((-35)TTGACA(-30)), and the extended -10 ((-15)TGn(-13)) are recognized as double stranded binding elements, whereas the -5 nontemplate G is recognized in the context of single-stranded DNA at the transcription bubble. Furthermore, the -10 element ((-12)TATAAT(-7)) is recognized as both double strand DNA for the T:A bp at position -12 and as nontemplate, single-strand DNA from positions -11 to -7. The single-strand sequences at positions -11 to -7 as well as the -5 contribute to later steps in transcription initiation that involve isomerization of polymerase and separation of the promoter DNA around the transcription start site. Recent work has demonstrated that the double strand elements may be used in various combinations to yield an effective promoter. Thus, while some minimal number of contacts is required for promoter function, polymerase allows the elements to be mixed and matched. Interestingly, which particular elements are used does not appear to fundamentally alter the transcription bubble generated in the stable complex. In this review, we discuss the multiple steps involved in forming a transcriptionally competent polymerase/promoter complex, and we examine what is known about polymerase recognition of core promoter elements. We suggest that considering promoter elements according to their involvement in early (polymerase binding) or later (polymerase isomerization) steps in transcription initiation rather than simply from their match to conventional promoter consensus sequences is a more instructive form of promoter classification.
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33
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Stewart V, Bledsoe PJ. Fnr-, NarP- and NarL-dependent regulation of transcription initiation from the Haemophilus influenzae Rd napF (periplasmic nitrate reductase) promoter in Escherichia coli K-12. J Bacteriol 2005; 187:6928-35. [PMID: 16199562 PMCID: PMC1251606 DOI: 10.1128/jb.187.20.6928-6935.2005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Periplasmic nitrate reductase (napFDAGHBC operon product) functions in anaerobic respiration. Transcription initiation from the Escherichia coli napF operon control region is activated by the Fnr protein in response to anaerobiosis and by the NarQ-NarP two-component regulatory system in response to nitrate or nitrite. The binding sites for the Fnr and phospho-NarP proteins are centered at positions -64.5 and -44.5, respectively, with respect to the major transcription initiation point. The E. coli napF operon is a rare example of a class I Fnr-activated transcriptional control region, in which the Fnr protein binding site is located upstream of position -60. To broaden our understanding of napF operon transcriptional control, we studied the Haemophilus influenzae Rd napF operon control region, expressed as a napF-lacZ operon fusion in the surrogate host E. coli. Mutational analysis demonstrated that expression required binding sites for the Fnr and phospho-NarP proteins centered at positions -81.5 and -42.5, respectively. Transcription from the E. coli napF operon control region is activated by phospho-NarP but antagonized by the orthologous protein, phospho-NarL. By contrast, expression from the H. influenzae napF-lacZ operon fusion in E. coli was stimulated equally well by nitrate in both narP and narL null mutants, indicating that phospho-NarL and -NarP are equally effective regulators of this promoter. Overall, the H. influenzae napF operon control region provides a relatively simple model for studying synergistic transcription by the Fnr and phospho-NarP proteins acting from class I and class II locations, respectively.
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Affiliation(s)
- Valley Stewart
- Section of Microbiology, University of California, One Shields Avenue, Davis, CA 95616-8665, USA.
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34
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Magasanik B. Origins. J Biol Chem 2005; 280:22557-9. [PMID: 15840567 DOI: 10.1074/jbc.x500003200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Boris Magasanik
- Department of Biochemistry, Massachusetts Institute of Technology, Cambridge, 02139-4307, USA.
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Stewart V, Chen LL, Wu HC. Response to culture aeration mediated by the nitrate and nitrite sensor NarQ of Escherichia coli K-12. Mol Microbiol 2004; 50:1391-9. [PMID: 14622424 DOI: 10.1046/j.1365-2958.2003.03776.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Respiratory enzyme synthesis in enterobacteria is controlled in response to electron acceptor availability. The iron-sulphur protein Fnr and the sensor-regulator proteins ArcB-ArcA control respiratory gene transcription in response to oxygen and quinone pool redox status respectively. The sensor-regulator proteins NarX-NarL and NarQ-NarP control anaerobic respiratory gene expression in response to nitrate and nitrite. Our laboratory recently engineered the lac operon to replace the primary operator O1-lac with the NarL and NarP protein binding site from the nirB operon. Expression of the lacZ gene from this construct is repressed by nitrate in Nar+ strains. Here, we found that lacZ gene expression was repressed in aerated cultures of narQ+narX null strains. This repression was not observed in narX+narQ+ or narX+narQ null strains. Thus, the NarQ sensor responds to aeration as well as to nitrate and nitrite. The NarX and NarQ sensors are composed of three distinct modules: an amino-terminal sensory module, a carboxyl-terminal transmitter module and a central module of unknown function. Experiments with NarX-NarQ hybrid proteins suggest that the NarQ protein central module is necessary for response to aeration. The physiological significance of this additional sensory role for the NarQ sensor remains obscure.
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Affiliation(s)
- Valley Stewart
- Section of Microbiology, University of California, One Shields Ave, Davis, CA 95616-8665, USA.
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36
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Kuo JT, Chang YJ, Tseng CP. Growth rate regulation of lac operon expression in Escherichia coli is cyclic AMP dependent. FEBS Lett 2003; 553:397-402. [PMID: 14572658 DOI: 10.1016/s0014-5793(03)01071-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In contrast to the ribosomal RNA gene expression increasing with growth rate, transcription of the lac operon is downregulated by cell growth rate. In continuous culture, growth rate regulation of lac promoter was independent of carbon substrate used and its location on the chromosome. Since the lac operon is activated by cyclic adenosine monophosphate (cAMP), which decreases with increasing cell growth rate, expression of plac-lacZ reporter fusion was analyzed in cya mutant under various growth conditions. The results demonstrated that expression of plac-lacZ in cya mutant was both lower and growth rate independent. In addition, ppGpp (guanosine tetraphosphate) was not involved in the mechanism of growth rate regulation of the lac promoter. Thus, the results of this study indicate that cAMP mediates the growth rate-dependent regulation of lac operon expression in Escherichia coli.
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Affiliation(s)
- Jong-Tar Kuo
- Department of Biological Science and Technology, National Chiao Tung University, 75 PO-Ai Street, Hsin-Chu, R.O.C., Taiwan
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37
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Lee K, Cohen SN. A Streptomyces coelicolor functional orthologue of Escherichia coli RNase E shows shuffling of catalytic and PNPase-binding domains. Mol Microbiol 2003; 48:349-60. [PMID: 12675796 DOI: 10.1046/j.1365-2958.2003.03435.x] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Previous work has detected an RNase E-like endoribonucleolytic activity in cell extracts obtained from Streptomyces. Here, we identify a Streptomyces coelicolor gene, rns, encoding a 140 kDa protein (RNase ES) that shows endoribonucleolytic cleavage specificity characteristic of RNase E, confers viability on and allows propagation of Escherichia coli cells lacking RNase E and accomplishes RNase E-like regulation of plasmid copy number in E. coli. However, notwithstanding its complementation of rne-deleted E. coli, RNase ES did not accurately process 9S rRNA from E. coli. Additionally, whereas RNase E is normally required for E. coli survival, rns is not an essential gene in S. coelicolor. Deletion analysis mapped the catalytic domain of RNase ES near its centre and showed that regions located near the RNase ES termini interact with an S. coelicolor homologue of polynucleotide phosphorylase (PNPase) - a major component of E. coli RNase E-based degradosomes. The interacting arginine- and proline-rich segments resemble the C-terminally located degradosome scaffold region of E. coli RNase E. Our results indicate that RNase ES is a structurally shuffled RNase E homologue showing evolutionary conservation of functional RNase E-like enzymatic activity, and suggest the existence of degradosome-like complexes in Gram-positive bacteria.
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Affiliation(s)
- Kangseok Lee
- Department of Genetics, Stanford University School of Medicine, Room M322, Stanford University Medical Center, Stanford, CA 94305-5120, USA
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38
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Stewart V, Bledsoe PJ. Synthetic lac operator substitutions for studying the nitrate- and nitrite-responsive NarX-NarL and NarQ-NarP two-component regulatory systems of Escherichia coli K-12. J Bacteriol 2003; 185:2104-11. [PMID: 12644479 PMCID: PMC151514 DOI: 10.1128/jb.185.7.2104-2111.2003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The NarX and NarQ sensor-histidine kinases control phosphorylation of the NarL and NarP response regulators in response to the respiratory oxidants nitrate and nitrite. Target operon transcription is activated by the Fnr protein in response to anaerobiosis, and it is further activated and/or repressed by the phospho-NarL and phospho-NarP proteins, which bind to heptamer DNA sequences. The location and arrangement of heptamers vary widely among different target operon control regions. We have constructed a series of monocopy lac operon control region constructs in which the primary operator O1-lac has been replaced by 7-2-7 heptamer pairs from the nrfA, nirB, napF, and fdnG operon control regions. These constructs provide tools for dissecting various aspects of ligand interactions with sensor-kinases, sensor interactions with response regulators, and phospho-response regulator interactions with DNA targets. Expression of the lacZ gene from these constructs was repressed to various degrees by nitrate and nitrite. In response to nitrate, the nrfA and nirB operon 7-2-7 heptamer pairs at operator O1 each mediated greater than 100-fold repression of lacZ gene expression, whereas the napF operon 7-2-7 heptamer pair mediated approximately tenfold repression. Introduction of narL, narP, narX, and narQ null alleles in various combinations allowed the in vivo interactions between different sensor-regulator pairs to be evaluated and compared.
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Affiliation(s)
- Valley Stewart
- Section of Microbiology, University of California, Davis, California 95616-8665, USA.
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39
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Fenton MS, Gralla JD. Function of the bacterial TATAAT -10 element as single-stranded DNA during RNA polymerase isomerization. Proc Natl Acad Sci U S A 2001; 98:9020-5. [PMID: 11470900 PMCID: PMC55366 DOI: 10.1073/pnas.161085798] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The bacterial TATAAT -10 region sequence was the first promoter element to be identified, but how it functions is still not clear. Because the duplex element is melted during initiation, the effects of substitutions were studied in both single-and double-strand contexts. Band-shift results were particularly unexpected in the context of melted DNA. The effect of the lac UV5-melted -10 region on polymerase binding was found to include a large sequence nonspecific contribution. Instead the dominant role of single-stranded -10 region nucleotides was in directing the isomerization of the RNA polymerase to its heparin resistant form. This role becomes minimal when the melting is extended beyond the -10 region to encompass the transcription start site, as in the final open complex. The duplex binding results are in agreement with previous reports that showed positions -12T and -11A are of primary importance for promoter recognition. Thus the consensus -10 region sequences function in two ways, both before full promoter melting. They stabilize initial polymerase binding via duplex interactions and subsequently as single-stranded DNA they promote enzyme isomerization to the functional form.
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Affiliation(s)
- M S Fenton
- Department of Chemistry and Biochemistry and Molecular Biology Institute, University of California, Post Office Box 951569, Los Angeles, CA 90095-1569, USA
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40
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Abstract
An alternative and facile delivery system for T7 RNA polymerase has been devised and constructed. T7 gene 1 has been placed under control of the araBAD promoter element regulated by the AraC protein. Cotransformation of the resultant plasmid, pTara, with one containing a target gene under T7 promoter-regulated expression potentially allows repression by glucose and induction by arabinose in the range of 0.5 to 20 mM sugar concentration. To demonstrate the efficacy of this expression system, the p53 gene under T7 promoter control in two different plasmids was expressed in Escherichia coli using pTara as the source of T7 RNA polymerase. Repression and induction of p53 were achieved in both a lower and higher copy number plasmid, although the levels of induction were higher with the lower copy number expression vector. Cotransformation of an expression plasmid with pTara provides a low-cost method of T7 RNA polymerase-regulated expression that can be fine-tuned using glucose and arabinose concentrations to balance protein expression with potential solubility or toxicity problems.
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Affiliation(s)
- D R Wycuff
- Department of Biochemistry, Rice University, Houston, Texas, 77251-1892, USA
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41
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Phillips DR, Cullinane CM, Crothers DM. An in vitro transcription assay for probing drug-DNA interactions at individual drug sites. Mol Biotechnol 1998; 10:63-75. [PMID: 9779423 DOI: 10.1007/bf02745863] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
An in vitro transcription assay of drug-DNA interactions has been described and is based largely on the stable lac UV5-initiated transcription complex. This system utilizes a synchronized population of radiolabeled nascent RNA 10 nucleotides long. Reaction of this initiated transcription complex with drug and subsequent elongation of the nascent RNA by Escherichia coli RNA polymerase, reveals blockages at drug binding sites. From these blockages it is possible to obtain four features of the drug-DNA interaction: the sequence of preferred drug binding sites, the relative drug occupancy at each binding site, the drug dissociation rate at each site, and the probability of drug-induced termination of transcription at each site. The unidirectional transcription assay has been extended to a two-promoter, counter-directed system, which yields a bidirectional transcription footprint of drug sites.
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Affiliation(s)
- D R Phillips
- Department of Biochemistry, La Trobe University, Bundoora, Victoria, Australia
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42
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Van Etten WJ, Janssen GR. An AUG initiation codon, not codon-anticodon complementarity, is required for the translation of unleadered mRNA in Escherichia coli. Mol Microbiol 1998; 27:987-1001. [PMID: 9535088 DOI: 10.1046/j.1365-2958.1998.00744.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We determined the in vivo translational efficiency of 'unleadered' lacZ compared with a conventionally leadered lacZ with and without a Shine-Dalgarno (SD) sequence in Escherichia coli and found that changing the SD sequence of leadered lacZ from the consensus 5'-AGGA-3' to 5'-UUUU-3' results in a 15-fold reduction in translational efficiency; however, removing the leader altogether results in only a twofold reduction. An increase in translation coincident with the removal of the leader lacking a SD sequence suggests the existence of stronger or novel translational signals within the coding sequence in the absence of the leader. We examined, therefore, a change in the translational signals provided by altering the AUG initiation codon to other naturally occurring initiation codons (GUG, UUG, CUG) in the presence and absence of a leader and find that mRNAs lacking leader sequences are dependent upon an AUG initiation codon, whereas leadered mRNAs are not. This suggests that mRNAs lacking leader sequences are either more dependent on perfect codon-anticodon complementarity or require an AUG initiation codon in a sequence-specific manner to form productive initiation complexes. A mutant initiator tRNA with compensating anticodon mutations restored expression of leadered, but not unleadered, mRNAs with UAG start codons, indicating that codon-anticodon complementarity was insufficient for the translation of mRNA lacking leader sequences. These data suggest that a cognate AUG initiation codon specifically serves as a stronger and different translational signal in the absence of an untranslated leader.
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Affiliation(s)
- W J Van Etten
- Department of Microbiology, Miami University, Oxford, OH 45056, USA
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43
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Kimata K, Takahashi H, Inada T, Postma P, Aiba H. cAMP receptor protein-cAMP plays a crucial role in glucose-lactose diauxie by activating the major glucose transporter gene in Escherichia coli. Proc Natl Acad Sci U S A 1997; 94:12914-9. [PMID: 9371775 PMCID: PMC24238 DOI: 10.1073/pnas.94.24.12914] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The inhibition of beta-galactosidase expression in a medium containing both glucose and lactose is a typical example of the glucose effect in Escherichia coli. We studied the glucose effect in the lacL8UV5 promoter mutant, which is independent of cAMP and cAMP receptor protein (CRP). A strong inhibition of beta-galactosidase expression by glucose and a diauxic growth were observed when the lacL8UV5 cells were grown on a glucose-lactose medium. The addition of isopropyl beta-D-thiogalactoside to the culture medium eliminated the glucose effect. Disruption of the crr gene or overproduction of LacY also eliminated the glucose effect. These results are fully consistent with our previous finding that the glucose effect in wild-type cells growing in a glucose-lactose medium is not due to the reduction of CRP-cAMP levels but is due to the inducer exclusion. We found that the glucose effect in the lacL8UV5 cells was no longer observed when either the crp or the cya gene was disrupted. Evidence suggested that CRP-cAMP may not enhance directly the lac repressor action in vivo. Northern blot analysis revealed that the mRNA for ptsG, a major glucose transporter gene, was markedly reduced in a delta crp or delta cya background. The constitutive expression of the ptsG gene by the introduction of a multicopy plasmid restored the glucose effect in delta cya or delta crp cells. We conclude that CRP-cAMP plays a crucial role in inducer exclusion, which is responsible for the glucose-lactose diauxie, by activating the expression of the ptsG gene.
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Affiliation(s)
- K Kimata
- Department of Molecular Biology, School of Science, Nagoya University, Chikusa, Japan
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44
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Abstract
Analysis of the chromosomic beta-galactosidase activity in strains of Escherichia coli with and without plasmids indicated that plasmid maintenance enhances gene expression. Cyclic AMP (cAMP) determinations confirmed that the gene enhancement observed in strains carrying plasmids was due to a small increase in the intracellular concentration of cAMP. Also, cells carrying plasmids displayed higher specific glucose uptake rates than did cells without plasmids. The increases in the expression of beta-galactosidase and the glucose uptake rate suggest a cAMP-mediated release of the glucose effect due to plasmid maintenance. Our results suggested that this effect is independent of the host and type and number of plasmids.
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Affiliation(s)
- J C Diaz-Ricci
- Departamento de Bioquímica de la Nutrición, Instituto Superior de Investigaciones Biológicas (CONICET-UNT), Tucumán, Argentina
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45
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Sia EA, Roberts RC, Easter C, Helinski DR, Figurski DH. Different relative importances of the par operons and the effect of conjugal transfer on the maintenance of intact promiscuous plasmid RK2. J Bacteriol 1995; 177:2789-97. [PMID: 7751288 PMCID: PMC176950 DOI: 10.1128/jb.177.10.2789-2797.1995] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The par region of the broad-host-range, IncP alpha plasmid RK2 has been implicated as a stability determinant by its ability to enhance the maintenance of mini-RK2 plasmids or heterologous replicons in a growing population of host cells. The region consists of two operons: parCBA, which encodes a multimer resolution system, and parDE, which specifies a postsegregational response mechanism that is toxic to plasmidless segregants. To assess the importance of this region to the stable maintenance of the complete RK2 plasmid in different hosts, we used the vector-mediated excision (VEX) deletion system to specifically remove the entire par region or each operon separately from an otherwise intact RK2 plasmid carrying a lacZ marker. The par region was found to be important to stable maintenance of RK2lac (pRK2526) in Escherichia coli and five other gram-negative hosts (Agrobacterium tumefaciens, Azotobacter vinelandii, Acinetobacter calcoaceticus, Caulobacter crescentus, and Pseudomonas aeruginosa). However, the relative importance of the parCBA and parDE operons varied from host to host. Deletion of parDE had no effect on the maintenance of pRK2526 in A. calcoaceticus, but it severely reduced pRK2526 maintenance in A. vinelandii and resulted in significant instability in the other hosts. Deletion of parCBA did not alter pRK2526 stability in E. coli, A. tumefaciens, or A. vinelandii but severely reduced plasmid maintenance in A. calcoaceticus and P. aeruginosa. In the latter two hosts and C. crescentus, the delta parCBA mutant caused a notable reduction in growth rate in the absence of selection for the plasmid, indicating that instability resulting from the absence of parCBA may trigger the postsegregational response mediated by parDE. We also examined the effect of the conjugal transfer system on RK2 maintenance in E. coli. Transfer-defective traJ and traG mutants of pRK2526 were stably maintained in rapidly growing broth cultures. On solid medium, which should be optimal for IncP-mediated conjugation, colonies from cells containing the pRK2526 tra mutants displayed significant numbers of white (Lac-) sectors on X-Gal (5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside) plates, whereas sectors appeared rarely in colonies from tra+ plasmid-containing cells. Both the traJ and traG mutations further reduced the maintenance of the already unstable deltapar derivative. Thus, these experiments with defined mutations in an intact RK2 plasmid have revealed (i) that the par region allows RK2 to adapt to the different requirements for stable maintenance in various hosts and (ii) that conjugal transfer can contribute to the maintenance of RK2 in a growing population, particularly under conditions that are favorable to RK2 transfer.
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Affiliation(s)
- E A Sia
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA
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46
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Tang H, Severinov K, Goldfarb A, Fenyo D, Chait B, Ebright RH. Location, structure, and function of the target of a transcriptional activator protein. Genes Dev 1994; 8:3058-67. [PMID: 8001824 DOI: 10.1101/gad.8.24.3058] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We have isolated and characterized single-amino-acid substitution mutants of RNA polymerase alpha subunit defective in CAP-dependent transcription at the lac promoter but not defective in CAP-independent transcription. Our results establish that (1) amino acids 258-265 of alpha constitute an "activation target" essential for CAP-dependent transcription at the lac promoter but not essential for CAP-independent transcription, (2) amino acid 261 is the most critical amino acid of the activation target, (3) amino acid 261 is distinct from the determinants for alpha-DNA interaction, and (4) the activation target may fold as a surface amphipathic alpha-helix. We propose a model for transcriptional activation at the lac promoter that integrates these and other recent results regarding transcriptional activation and RNA polymerase structure and function.
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Affiliation(s)
- H Tang
- Department of Chemistry, Rutgers University, New Brunswick, New Jersey 08855
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47
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Blomfield IC, Calie PJ, Eberhardt KJ, McClain MS, Eisenstein BI. Lrp stimulates phase variation of type 1 fimbriation in Escherichia coli K-12. J Bacteriol 1993; 175:27-36. [PMID: 8093239 PMCID: PMC196094 DOI: 10.1128/jb.175.1.27-36.1993] [Citation(s) in RCA: 124] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The phase variation of type 1 fimbriation in Escherichia coli is associated with the inversion of a short DNA element. This element (switch) acts in cis to control transcription of fimA, the major fimbrial subunit gene. Thus, fimA is transcribed when the switch is in one orientation (the on orientation) but not the other (the off orientation). The fim inversion requires either fimB (on-to-off or off-to-on inversion) or fimE (on-to-off inversion only), as well as integration host factor, and is also influenced by the abundant DNA-binding protein H-NS. Here we report that an additional gene, lrp, a factor known to influence the expression of both Pap and K99 fimbriae, is also required for normal activity of the fim switch. The frequencies of both fimB-promoted and fimE-promoted inversions, and consequently the phase variation of type 1 fimbriation, are lower in lrp mutants. Lrp affects slightly the transcription of both fimB (which is increased) and fimE (which is decreased). We believe that these alterations in fimB and fimE transcription alone are unlikely to account for the sharp reduction in switching found in lrp mutants.
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Affiliation(s)
- I C Blomfield
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48109
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48
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Heterologous cooperativity in Escherichia coli. The CytR repressor both contacts DNA and the cAMP receptor protein when binding to the deoP2 promoter. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)55198-x] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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49
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Ishiyama J. Isolation of mutants with improved production of cAMP from Microbacterium sp. no. 205 (ATCC 21376). Appl Microbiol Biotechnol 1991; 34:359-63. [PMID: 1369318 DOI: 10.1007/bf00170060] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Mutants were isolated from Microbacterium sp. no. 205 (ATCC 21376) producing 13-30 mM cyclic adenosine 3',5'-monophosphate (cAMP) by salvage biosynthesis, through sequential improvements of the bacterium for the purpose of improving cAMP production. The mutants produced 50-75 mM cAMP on 100 mM inosine 5'-monophosphate as a precursor. Mutants resistant to the inhibition of growth by cAMP at high concentrations were isolated; the resistance was one of four characteristics effective for improved production of cAMP.
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Affiliation(s)
- J Ishiyama
- Research and Development Division, Kikkoman Corporation, Chiba-ken, Japan
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50
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Sasse-Dwight S, Gralla JD. KMnO4 as a probe for lac promoter DNA melting and mechanism in vivo. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)83152-0] [Citation(s) in RCA: 122] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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