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Perry TN, Souabni H, Rapisarda C, Fronzes R, Giusti F, Popot JL, Zoonens M, Gubellini F. BAmSA: Visualising transmembrane regions in protein complexes using biotinylated amphipols and electron microscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:466-477. [DOI: 10.1016/j.bbamem.2018.11.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 11/06/2018] [Accepted: 11/08/2018] [Indexed: 12/30/2022]
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52
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Varga JK, Tusnády GE. TMCrys: predict propensity of success for transmembrane protein crystallization. Bioinformatics 2018; 34:3126-3130. [PMID: 29718100 PMCID: PMC6137969 DOI: 10.1093/bioinformatics/bty342] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Revised: 03/10/2018] [Accepted: 04/25/2018] [Indexed: 11/30/2022] Open
Abstract
Motivation Transmembrane proteins (TMPs) are crucial in the life of the cells. As they have special properties, their structure is hard to determine--the PDB database consists of 2% TMPs, despite the fact that they are predicted to make up to 25% of the human proteome. Crystallization prediction methods were developed to aid the target selection for structure determination, however, there is a need for a TMP specific service. Results Here, we present TMCrys, a crystallization prediction method that surpasses existing prediction methods in performance thanks to its specialization for TMPs. We expect TMCrys to improve target selection of TMPs. Availability and implementation https://github.com/brgenzim/tmcrys. Supplementary information Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Julia K Varga
- ‘Momentum’ Membrane Protein Bioinformatics Research Group, Institute of Enzymology, Research Center of Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary
| | - Gábor E Tusnády
- ‘Momentum’ Membrane Protein Bioinformatics Research Group, Institute of Enzymology, Research Center of Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary
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53
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Jamin N, Garrigos M, Jaxel C, Frelet-Barrand A, Orlowski S. Ectopic Neo-Formed Intracellular Membranes in Escherichia coli: A Response to Membrane Protein-Induced Stress Involving Membrane Curvature and Domains. Biomolecules 2018; 8:biom8030088. [PMID: 30181516 PMCID: PMC6163855 DOI: 10.3390/biom8030088] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 08/31/2018] [Accepted: 08/31/2018] [Indexed: 11/16/2022] Open
Abstract
Bacterial cytoplasmic membrane stress induced by the overexpression of membrane proteins at high levels can lead to formation of ectopic intracellular membranes. In this review, we report the various observations of such membranes in Escherichia coli, compare their morphological and biochemical characterizations, and we analyze the underlying molecular processes leading to their formation. Actually, these membranes display either vesicular or tubular structures, are separated or connected to the cytoplasmic membrane, present mono- or polydispersed sizes and shapes, and possess ordered or disordered arrangements. Moreover, their composition differs from that of the cytoplasmic membrane, with high amounts of the overexpressed membrane protein and altered lipid-to-protein ratio and cardiolipin content. These data reveal the importance of membrane domains, based on local specific lipid⁻protein and protein⁻protein interactions, with both being crucial for local membrane curvature generation, and they highlight the strong influence of protein structure. Indeed, whether the cylindrically or spherically curvature-active proteins are actively curvogenic or passively curvophilic, the underlying molecular scenarios are different and can be correlated with the morphological features of the neo-formed internal membranes. Delineating these molecular mechanisms is highly desirable for a better understanding of protein⁻lipid interactions within membrane domains, and for optimization of high-level membrane protein production in E. coli.
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Affiliation(s)
- Nadège Jamin
- Institute for Integrative Biology of the Cell (I2BC), CEA/Institut des Sciences du Vivant Fréderic-Joliot/SB2SM, CNRS UMR 9198, Université Paris-Sud, Université Paris-Saclay, 91191 Gif sur Yvette CEDEX, France.
| | - Manuel Garrigos
- Institute for Integrative Biology of the Cell (I2BC), CEA/Institut des Sciences du Vivant Fréderic-Joliot/SB2SM, CNRS UMR 9198, Université Paris-Sud, Université Paris-Saclay, 91191 Gif sur Yvette CEDEX, France.
| | - Christine Jaxel
- Institute for Integrative Biology of the Cell (I2BC), CEA/Institut des Sciences du Vivant Fréderic-Joliot/SB2SM, CNRS UMR 9198, Université Paris-Sud, Université Paris-Saclay, 91191 Gif sur Yvette CEDEX, France.
| | - Annie Frelet-Barrand
- Institut FEMTO-ST, UMR CNRS 6174, Université Bourgogne Franche-Comté, 15B avenue des Montboucons, 25030 Besançon CEDEX, France.
| | - Stéphane Orlowski
- Institute for Integrative Biology of the Cell (I2BC), CEA/Institut des Sciences du Vivant Fréderic-Joliot/SB2SM, CNRS UMR 9198, Université Paris-Sud, Université Paris-Saclay, 91191 Gif sur Yvette CEDEX, France.
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54
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Lu M, Zhao X, Xing H, Xun Z, Yang T, Cai C, Wang D, Ding P. Liposome-chaperoned cell-free synthesis for the design of proteoliposomes: Implications for therapeutic delivery. Acta Biomater 2018; 76:1-20. [PMID: 29625253 DOI: 10.1016/j.actbio.2018.03.043] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 03/20/2018] [Accepted: 03/27/2018] [Indexed: 12/12/2022]
Abstract
Cell-free (CF) protein synthesis has emerged as a powerful technique platform for efficient protein production in vitro. Liposomes have been widely studied as therapeutic carriers due to their biocompatibility, biodegradability, low toxicity, flexible surface manipulation, easy preparation, and higher cargo encapsulation capability. However, rapid immune clearance, insufficient targeting capacity, and poor cytoplasmic delivery efficiency substantially restrict their clinical application. The incorporation of functional membrane proteins (MPs) or peptides allows the transfer of biological properties to liposomes and imparts them with improved circulation, increased targeting, and efficient intracellular delivery. Liposome-chaperoned CF synthesis enables production of proteoliposomes in one-step reaction, which not only substantially simplifies the production procedure but also keeps protein functionality intact. Building off these observations, proteoliposomes with integrated MPs represent an excellent candidate for therapeutic delivery. In this review, we describe recent advances in CF synthesis with emphasis on detailing key factors for improving CF expression efficiency. Furthermore, we provide insights into strategies for rational design of proteoliposomal nanodelivery systems via CF synthesis. STATEMENT OF SIGNIFICANCE Liposome-chaperoned CF synthesis has emerged as a powerful approach for the design of recombinant proteoliposomes in one-step reaction. The incorporation of bioactive MPs or peptides into liposomes via CF synthesis can facilitate the development of proteoliposomal nanodelivery systems with improved circulation, increased targeting, and enhanced cellular delivery capacity. Moreover, by adapting lessons learned from natural delivery vehicles, novel bio-inspired proteoliposomes with enhanced delivery properties could be produced in CF systems. In this review, we first give an overview of CF synthesis with focus on enhancing protein expression in liposome-chaperoned CF systems. Furthermore, we intend to provide insight into harnessing CF-synthesized proteoliposomes for efficient therapeutic delivery.
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55
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Angius F, Ilioaia O, Amrani A, Suisse A, Rosset L, Legrand A, Abou-Hamdan A, Uzan M, Zito F, Miroux B. A novel regulation mechanism of the T7 RNA polymerase based expression system improves overproduction and folding of membrane proteins. Sci Rep 2018; 8:8572. [PMID: 29872064 PMCID: PMC5988807 DOI: 10.1038/s41598-018-26668-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Accepted: 05/04/2018] [Indexed: 02/03/2023] Open
Abstract
Membrane protein (MP) overproduction is one of the major bottlenecks in structural genomics and biotechnology. Despite the emergence of eukaryotic expression systems, bacteria remain a cost effective and powerful tool for protein production. The T7 RNA polymerase (T7RNAP)-based expression system is a successful and efficient expression system, which achieves high-level production of proteins. However some foreign MPs require a fine-tuning of their expression to minimize the toxicity associated with their production. Here we report a novel regulation mechanism for the T7 expression system. We have isolated two bacterial hosts, namely C44(DE3) and C45(DE3), harboring a stop codon in the T7RNAP gene, whose translation is under the control of the basal nonsense suppressive activity of the BL21(DE3) host. Evaluation of hosts with superfolder green fluorescent protein (sfGFP) revealed an unprecedented tighter control of transgene expression with a marked accumulation of the recombinant protein during stationary phase. Analysis of a collection of twenty MP fused to GFP showed an improved production yield and quality of several bacterial MPs and of one human monotopic MP. These mutant hosts are complementary to the other existing T7 hosts and will increase the versatility of the T7 expression system.
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Affiliation(s)
- Federica Angius
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, CNRS, University Paris Diderot, Sorbonne Paris Cité, Institut de Biologie Physico-Chimique, Paris, France
| | - Oana Ilioaia
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, CNRS, University Paris Diderot, Sorbonne Paris Cité, Institut de Biologie Physico-Chimique, Paris, France
| | - Amira Amrani
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, CNRS, University Paris Diderot, Sorbonne Paris Cité, Institut de Biologie Physico-Chimique, Paris, France
| | - Annabelle Suisse
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, CNRS, University Paris Diderot, Sorbonne Paris Cité, Institut de Biologie Physico-Chimique, Paris, France.,Helen L. and Martin S. Kimmel Center at the Skirball Institute for Biomolecular Medicine and Department of Cell Biology, NYU School of Medicine, New York, USA
| | - Lindsay Rosset
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, CNRS, University Paris Diderot, Sorbonne Paris Cité, Institut de Biologie Physico-Chimique, Paris, France
| | - Amélie Legrand
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, CNRS, University Paris Diderot, Sorbonne Paris Cité, Institut de Biologie Physico-Chimique, Paris, France
| | - Abbas Abou-Hamdan
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, CNRS, University Paris Diderot, Sorbonne Paris Cité, Institut de Biologie Physico-Chimique, Paris, France.,Institut de Biologie Intégrative de la Cellule, CNRS, Gif sur Yvette, France
| | - Marc Uzan
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, CNRS, University Paris Diderot, Sorbonne Paris Cité, Institut de Biologie Physico-Chimique, Paris, France
| | - Francesca Zito
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, CNRS, University Paris Diderot, Sorbonne Paris Cité, Institut de Biologie Physico-Chimique, Paris, France
| | - Bruno Miroux
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, CNRS, University Paris Diderot, Sorbonne Paris Cité, Institut de Biologie Physico-Chimique, Paris, France.
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56
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Satheeshkumar PK, Anu PV, Junaida MI, Madanan MG, Jebasingh T, Nair AJ, Nair GA, Nair GPM, Sudhakaran PR. Expression of Leptospira membrane proteins Signal Peptidase (SP) and Leptospira Endostatin like A (Len A) in BL-21(DE3) is toxic to the host cells. J Genet Eng Biotechnol 2018; 16:393-398. [PMID: 30733752 PMCID: PMC6353657 DOI: 10.1016/j.jgeb.2018.01.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 01/18/2018] [Accepted: 01/24/2018] [Indexed: 02/06/2023]
Abstract
Heterologous expression of Integral Membrane Proteins (IMPs) is reported to be toxic to the host system in many studies. Even though there are reports on various concerns like transformation efficiency, growth properties, protein toxicity, inefficient expression and protein degradation in IMP overexpression, no studies so far addressed these issues in a comprehensive way. In the present study, two transmembrane proteins of the pathogen Leptospira interrogans, namely Signal peptidase (SP), and Leptospira Endostatin like A (Len-A) were taken along with a cytosolic protein Hydrolase (HYD) to assess the differences in transformation efficiency, protein toxicity, and protein stability when over expressed in Escherichia coli (E. coli). Bioinformatics analysis to predict the transmembrane localization indicated that both SP and Len are targeted to the membrane. The three proteins were expressed in full length in the E. coli expression strain, BL 21 (DE3). Significant changes were observed for the strains transformed with IMP genes under the parameters analysed such as, the transformation efficiency, survival of colonies on IPTG-plate, culture growth kinetics and protein expression compared to the strain harbouring the cytosolic protein gene.
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Affiliation(s)
- Padikara K Satheeshkumar
- Interuniversity Centre for Genomics and Gene Technology, Department of Biotechnology, University of Kerala, Trivandrum, Kerala, India
| | - Prasannan V Anu
- Interuniversity Centre for Genomics and Gene Technology, Department of Biotechnology, University of Kerala, Trivandrum, Kerala, India
| | - Mohmed I Junaida
- Interuniversity Centre for Genomics and Gene Technology, Department of Biotechnology, University of Kerala, Trivandrum, Kerala, India
| | | | | | - Ananthakrishnan J Nair
- Interuniversity Centre for Genomics and Gene Technology, Department of Biotechnology, University of Kerala, Trivandrum, Kerala, India
| | - Gangaprasad A Nair
- Interuniversity Centre for Genomics and Gene Technology, Department of Biotechnology, University of Kerala, Trivandrum, Kerala, India
| | - Govinda Pillai M Nair
- Interuniversity Centre for Genomics and Gene Technology, Department of Biotechnology, University of Kerala, Trivandrum, Kerala, India
| | - Perumana R Sudhakaran
- Interuniversity Centre for Genomics and Gene Technology, Department of Biotechnology, University of Kerala, Trivandrum, Kerala, India
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57
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Balancing cellular redox metabolism in microbial electrosynthesis and electro fermentation - A chance for metabolic engineering. Metab Eng 2017; 45:109-120. [PMID: 29229581 DOI: 10.1016/j.ymben.2017.12.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Revised: 09/15/2017] [Accepted: 12/06/2017] [Indexed: 01/05/2023]
Abstract
More and more microbes are discovered that are capable of extracellular electron transfer, a process in which they use external electrodes as electron donors or acceptors for metabolic reactions. This feature can be used to overcome cellular redox limitations and thus optimizing microbial production. The technologies, termed microbial electrosynthesis and electro-fermentation, have the potential to open novel bio-electro production platforms from sustainable energy and carbon sources. However, the performance of reported systems is currently limited by low electron transport rates between microbes and electrodes and our limited ability for targeted engineering of these systems due to remaining knowledge gaps about the underlying fundamental processes. Metabolic engineering offers many opportunities to optimize these processes, for instance by genetic engineering of pathways for electron transfer on the one hand and target product synthesis on the other hand. With this review, we summarize the status quo of knowledge and engineering attempts around chemical production in bio-electrochemical systems from a microbe perspective. Challenges associated with the introduction or enhancement of extracellular electron transfer capabilities into production hosts versus the engineering of target compound synthesis pathways in natural exoelectrogens are discussed. Recent advances of the research community in both directions are examined critically. Further, systems biology approaches, for instance using metabolic modelling, are examined for their potential to provide insight into fundamental processes and to identify targets for metabolic engineering.
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58
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Jia B, Jeon CO. High-throughput recombinant protein expression in Escherichia coli: current status and future perspectives. Open Biol 2017; 6:rsob.160196. [PMID: 27581654 PMCID: PMC5008019 DOI: 10.1098/rsob.160196] [Citation(s) in RCA: 176] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 08/03/2016] [Indexed: 12/26/2022] Open
Abstract
The ease of genetic manipulation, low cost, rapid growth and number of previous studies have made Escherichia coli one of the most widely used microorganism species for producing recombinant proteins. In this post-genomic era, challenges remain to rapidly express and purify large numbers of proteins for academic and commercial purposes in a high-throughput manner. In this review, we describe several state-of-the-art approaches that are suitable for the cloning, expression and purification, conducted in parallel, of numerous molecules, and we discuss recent progress related to soluble protein expression, mRNA folding, fusion tags, post-translational modification and production of membrane proteins. Moreover, we address the ongoing efforts to overcome various challenges faced in protein expression in E. coli, which could lead to an improvement of the current system from trial and error to a predictable and rational design.
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Affiliation(s)
- Baolei Jia
- Department of Life Science, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Che Ok Jeon
- Department of Life Science, Chung-Ang University, Seoul 06974, Republic of Korea
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59
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Improving membrane protein expression and function using genomic edits. Sci Rep 2017; 7:13030. [PMID: 29026162 PMCID: PMC5638813 DOI: 10.1038/s41598-017-12901-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 09/08/2017] [Indexed: 11/08/2022] Open
Abstract
Expression of membrane proteins often leads to growth inhibition and perturbs central metabolism and this burden varies with the protein being overexpressed. There are also known strain backgrounds that allow greater expression of membrane proteins but that differ in efficacy across proteins. We hypothesized that for any membrane protein, it may be possible to identify a modified strain background where its expression can be accommodated with less burden. To directly test this hypothesis, we used a bar-coded transposon insertion library in tandem with cell sorting to assess genome-wide impact of gene deletions on membrane protein expression. The expression of five membrane proteins (CyoB, CydB, MdlB, YidC, and LepI) and one soluble protein (GST), each fused to GFP, was examined. We identified Escherichia coli mutants that demonstrated increased membrane protein expression relative to that in wild type. For two of the proteins (CyoB and CydB), we conducted functional assays to confirm that the increase in protein expression also led to phenotypic improvement in function. This study represents a systematic approach to broadly identify genetic loci that can be used to improve membrane protein expression, and our method can be used to improve expression of any protein that poses a cellular burden.
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60
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Yu S, Lai B, Plan MR, Hodson MP, Lestari EA, Song H, Krömer JO. Improved performance ofPseudomonas putidain a bioelectrochemical system through overexpression of periplasmic glucose dehydrogenase. Biotechnol Bioeng 2017; 115:145-155. [DOI: 10.1002/bit.26433] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 08/21/2017] [Accepted: 08/23/2017] [Indexed: 12/21/2022]
Affiliation(s)
- Shiqin Yu
- Centre for Microbial Electrochemical Systems (CEMES); The University of Queensland; St Lucia Brisbane Australia
- Advanced Water Management Centre (AWMC); The University of Queensland; St Lucia Brisbane Australia
| | - Bin Lai
- Centre for Microbial Electrochemical Systems (CEMES); The University of Queensland; St Lucia Brisbane Australia
- Advanced Water Management Centre (AWMC); The University of Queensland; St Lucia Brisbane Australia
- Systems Biotechnology Group, Department for Solar Materials (SOMA); Helmholtz Centre for Environmental Research UFZ; Leipzig Germany
| | - Manuel R. Plan
- Australian Institute for Bioengineering and Nanotechnology (AIBN); The University of Queensland; St Lucia Brisbane Australia
- Metabolomics Australia (Queensland Node); The University of Queensland; St Lucia Brisbane Australia
| | - Mark P. Hodson
- Australian Institute for Bioengineering and Nanotechnology (AIBN); The University of Queensland; St Lucia Brisbane Australia
- Metabolomics Australia (Queensland Node); The University of Queensland; St Lucia Brisbane Australia
| | - Endah A. Lestari
- School of Chemical and Molecular Biosciences; The University of Queensland; St Lucia Brisbane Australia
| | - Hao Song
- Key Laboratory of Systems Bioengineering, Ministry of Education, School of Chemical Engineering & Technology, and Collaborative Innovation Center of Chemical Science and Engineering (Tianjin); Tianjin University; Tianjin China
| | - Jens O. Krömer
- Centre for Microbial Electrochemical Systems (CEMES); The University of Queensland; St Lucia Brisbane Australia
- Advanced Water Management Centre (AWMC); The University of Queensland; St Lucia Brisbane Australia
- Systems Biotechnology Group, Department for Solar Materials (SOMA); Helmholtz Centre for Environmental Research UFZ; Leipzig Germany
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61
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Gialama D, Delivoria DC, Michou M, Giannakopoulou A, Skretas G. Functional Requirements for DjlA- and RraA-Mediated Enhancement of Recombinant Membrane Protein Production in the Engineered Escherichia coli Strains SuptoxD and SuptoxR. J Mol Biol 2017; 429:1800-1816. [PMID: 28501587 DOI: 10.1016/j.jmb.2017.05.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 04/30/2017] [Accepted: 05/04/2017] [Indexed: 12/17/2022]
Abstract
In previous work, we have generated the engineered Escherichia coli strains SuptoxD and SuptoxR, which upon co-expression of the effector genes djlA or rraA, respectively, are capable of suppressing the cytotoxicity caused by membrane protein (MP) overexpression and of producing dramatically enhanced yields for a variety of recombinant MPs of both prokaryotic and eukaryotic origin. Here, we investigated the functional requirements for DnaJ-like protein A (DjlA)- and regulator of ribonuclease activity A (RraA)-mediated enhancement of recombinant MP production in these strains and show that: (i) DjlA and RraA act independently, that is, the beneficial effects of each protein on recombinant MP production occur through a mechanism that does not involve the other, and in a non-additive manner; (ii) full-length and membrane-bound DjlA is required for exerting its beneficial effects on recombinant MP production in E. coli SuptoxD; (iii) the MP production-promoting properties of DjlA in SuptoxD involve the action of the molecular chaperone DnaK but do not rely on the activation of the regulation of capsular synthesis response, a well-established consequence of djlA overexpression; (iv) the observed RraA-mediated effects in E. coli SuptoxR involve the ribonucleolytic activity of RNase E, but not that of its paralogous ribonuclease RNase G; and (v) DjlA and RraA are unique among similar E. coli proteins in their ability to promote bacterial recombinant MP production. These observations provide important clues about the molecular requirements for suppressed toxicity and enhanced MP accumulation in SuptoxD/SuptoxR and will guide future studies aiming to decipher the exact mechanism of DjlA- and RraA-mediated enhancement of recombinant MP production in these strains.
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Affiliation(s)
- Dimitra Gialama
- Institute of Biology, Medicinal Chemistry & Biotechnology, National Hellenic Research Foundation, Athens, 11635, Greece; Laboratory of Biotechnology, School of Chemical Engineering, National Technical University of Athens, Athens, 15780, Greece
| | - Dafni Chrysanthi Delivoria
- Institute of Biology, Medicinal Chemistry & Biotechnology, National Hellenic Research Foundation, Athens, 11635, Greece; Laboratory of Biotechnology, School of Chemical Engineering, National Technical University of Athens, Athens, 15780, Greece
| | - Myrsini Michou
- Institute of Biology, Medicinal Chemistry & Biotechnology, National Hellenic Research Foundation, Athens, 11635, Greece; Department of Biochemistry and Biotechnology, University of Thessaly, Larissa, 41500, Greece
| | - Artemis Giannakopoulou
- Institute of Biology, Medicinal Chemistry & Biotechnology, National Hellenic Research Foundation, Athens, 11635, Greece
| | - Georgios Skretas
- Institute of Biology, Medicinal Chemistry & Biotechnology, National Hellenic Research Foundation, Athens, 11635, Greece.
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62
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Gialama D, Kostelidou K, Michou M, Delivoria DC, Kolisis FN, Skretas G. Development of Escherichia coli Strains That Withstand Membrane Protein-Induced Toxicity and Achieve High-Level Recombinant Membrane Protein Production. ACS Synth Biol 2017; 6:284-300. [PMID: 27797488 DOI: 10.1021/acssynbio.6b00174] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Membrane proteins perform critical cellular functions in all living organisms and constitute major targets for drug discovery. Escherichia coli has been the most popular overexpression host for membrane protein biochemical/structural studies. Bacterial production of recombinant membrane proteins, however, is typically hampered by poor cellular accumulation and severe toxicity for the host, which leads to low final biomass and minute volumetric yields. In this work, we aimed to rewire the E. coli protein-producing machinery to withstand the toxicity caused by membrane protein overexpression in order to generate engineered bacterial strains with the ability to achieve high-level membrane protein production. To achieve this, we searched for bacterial genes whose coexpression can suppress membrane protein-induced toxicity and identified two highly potent effectors: the membrane-bound DnaK cochaperone DjlA, and the inhibitor of the mRNA-degrading activity of the E. coli RNase E, RraA. E. coli strains coexpressing either djlA or rraA, termed SuptoxD and SuptoxR, respectively, accumulated markedly higher levels of final biomass and produced dramatically enhanced yields for a variety of prokaryotic and eukaryotic recombinant membrane proteins. In all tested cases, either SuptoxD, or SuptoxR, or both, outperformed the capabilities of commercial strains frequently utilized for recombinant membrane protein production purposes.
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Affiliation(s)
- Dimitra Gialama
- Institute of Biology, Medicinal Chemistry & Biotechnology, National Hellenic Research Foundation, Athens 11635, Greece
- Laboratory
of Biotechnology, School of Chemical Engineering, National Technical University of Athens, Athens 15780, Greece
| | - Kalliopi Kostelidou
- Institute of Biology, Medicinal Chemistry & Biotechnology, National Hellenic Research Foundation, Athens 11635, Greece
| | - Myrsini Michou
- Institute of Biology, Medicinal Chemistry & Biotechnology, National Hellenic Research Foundation, Athens 11635, Greece
| | - Dafni Chrysanthi Delivoria
- Institute of Biology, Medicinal Chemistry & Biotechnology, National Hellenic Research Foundation, Athens 11635, Greece
- Laboratory
of Biotechnology, School of Chemical Engineering, National Technical University of Athens, Athens 15780, Greece
| | - Fragiskos N. Kolisis
- Laboratory
of Biotechnology, School of Chemical Engineering, National Technical University of Athens, Athens 15780, Greece
| | - Georgios Skretas
- Institute of Biology, Medicinal Chemistry & Biotechnology, National Hellenic Research Foundation, Athens 11635, Greece
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63
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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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Musial-Siwek M, Jaffee MB, Imperiali B. Probing Polytopic Membrane Protein-Substrate Interactions by Luminescence Resonance Energy Transfer. J Am Chem Soc 2016; 138:3806-12. [PMID: 26918528 DOI: 10.1021/jacs.5b13426] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Integral membrane proteins play essential roles in all living systems; however, major technical hurdles challenge analyses of this class of proteins. Biophysical approaches that provide structural information to complement and leverage experimentally determined and computationally predicted structures are urgently needed. Herein we present the application of luminescence resonance energy transfer (LRET) for investigating the interactions of the polytopic membrane-bound oligosaccharyl transferases (OTases) with partner substrates. Monomeric OTases, such as the PglBs from Campylobacter jejuni and Campylobacter lari, catalyze transfer of glycans from membrane-associated undecaprenol diphosphate-linked substrates to proteins in the bacterial periplasm. LRET-based distance measurements are enabled by the inclusion of an encoded N-terminal lanthanide-binding tag (LBT), and LRET between the luminescent (LBT)-Tb(3+) donor complex and fluorescently labeled peptide and glycan substrates provides discrete distance measurements across the span of the membrane. LRET-based measurements of detergent-solubilized PglB from C. lari allowed direct comparison with the distances based on the previously reported the C. lari PglB crystal structure, thereby validating the approach in a defined system. Distance measurements between peptide and glycan substrates and the C. jejuni PglB offer new experimental information on substrate binding to the related, but structurally uncharacterized, eukaryotic OTase.
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Affiliation(s)
- Monika Musial-Siwek
- Departments of Biology and Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
| | - Marcie B Jaffee
- Departments of Biology and Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
| | - Barbara Imperiali
- Departments of Biology and Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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65
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Ude C, Ben-Dov N, Jochums A, Li Z, Segal E, Scheper T, Beutel S. Online analysis of protein inclusion bodies produced in E. coli by monitoring alterations in scattered and reflected light. Appl Microbiol Biotechnol 2016; 100:4147-59. [PMID: 26940052 DOI: 10.1007/s00253-016-7403-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Revised: 02/15/2016] [Accepted: 02/17/2016] [Indexed: 12/29/2022]
Abstract
The online monitoring of recombinant protein aggregate inclusion bodies during microbial cultivation is an immense challenge. Measurement of scattered and reflected light offers a versatile and non-invasive measurement technique. Therefore, we investigated two methods to detect the formation of inclusion bodies and monitor their production: (1) online 180° scattered light measurement (λ = 625 nm) using a sensor platform during cultivation in shake flask and (2) online measurement of the light reflective interference using a porous Si-based optical biosensor (SiPA). It could be shown that 180° scattered light measurement allows monitoring of alterations in the optical properties of Escherichia coli BL21 cells, associated with the formation of inclusion bodies during cultivation. A reproducible linear correlation between the inclusion body concentration of the non-fluorescent protein human leukemia inhibitory factor (hLIF) carrying a thioredoxin tag and the shift ("Δamp") in scattered light signal intensity was observed. This was also observed for the glutathione-S-transferase-tagged green fluorescent protein (GFP-GST). Continuous online monitoring of reflective interference spectra reveals a significant increase in the bacterium refractive index during hLIF production in comparison to a non-induced reference that coincide with the formation of inclusion bodies. These online monitoring techniques could be applied for fast and cost-effective screening of different protein expression systems.
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Affiliation(s)
- Christian Ude
- Institut für Technische Chemie, Gottfried Wilhelm Leibniz Universität Hannover, Callinstraße 5, 30167, Hannover, Germany
| | - Nadav Ben-Dov
- Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, 32000, Haifa, Israel
| | - André Jochums
- Institut für Technische Chemie, Gottfried Wilhelm Leibniz Universität Hannover, Callinstraße 5, 30167, Hannover, Germany
| | - Zhaopeng Li
- Institut für Technische Chemie, Gottfried Wilhelm Leibniz Universität Hannover, Callinstraße 5, 30167, Hannover, Germany
| | - Ester Segal
- Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, 32000, Haifa, Israel
| | - Thomas Scheper
- Institut für Technische Chemie, Gottfried Wilhelm Leibniz Universität Hannover, Callinstraße 5, 30167, Hannover, Germany
| | - Sascha Beutel
- Institut für Technische Chemie, Gottfried Wilhelm Leibniz Universität Hannover, Callinstraße 5, 30167, Hannover, Germany.
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66
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Cell Surface and Membrane Engineering: Emerging Technologies and Applications. J Funct Biomater 2015; 6:454-85. [PMID: 26096148 PMCID: PMC4493524 DOI: 10.3390/jfb6020454] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Revised: 06/08/2015] [Accepted: 06/12/2015] [Indexed: 12/31/2022] Open
Abstract
Membranes constitute the interface between the basic unit of life—a single cell—and the outside environment and thus in many ways comprise the ultimate “functional biomaterial”. To perform the many and often conflicting functions required in this role, for example to partition intracellular contents from the outside environment while maintaining rapid intake of nutrients and efflux of waste products, biological membranes have evolved tremendous complexity and versatility. This article describes how membranes, mainly in the context of living cells, are increasingly being manipulated for practical purposes with drug discovery, biofuels, and biosensors providing specific, illustrative examples. Attention is also given to biology-inspired, but completely synthetic, membrane-based technologies that are being enabled by emerging methods such as bio-3D printers. The diverse set of applications covered in this article are intended to illustrate how these versatile technologies—as they rapidly mature—hold tremendous promise to benefit human health in numerous ways ranging from the development of new medicines to sensitive and cost-effective environmental monitoring for pathogens and pollutants to replacing hydrocarbon-based fossil fuels.
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67
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Laurenceau R, Krasteva PV, Diallo A, Ouarti S, Duchateau M, Malosse C, Chamot-Rooke J, Fronzes R. Conserved Streptococcus pneumoniae spirosomes suggest a single type of transformation pilus in competence. PLoS Pathog 2015; 11:e1004835. [PMID: 25876066 PMCID: PMC4398557 DOI: 10.1371/journal.ppat.1004835] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Accepted: 03/26/2015] [Indexed: 11/18/2022] Open
Abstract
The success of S. pneumoniae as a major human pathogen is largely due to its remarkable genomic plasticity, allowing efficient escape from antimicrobials action and host immune response. Natural transformation, or the active uptake and chromosomal integration of exogenous DNA during the transitory differentiated state competence, is the main mechanism for horizontal gene transfer and genomic makeover in pneumococci. Although transforming DNA has been proposed to be captured by Type 4 pili (T4P) in Gram-negative bacteria, and a competence-inducible comG operon encoding proteins homologous to T4P-biogenesis components is present in transformable Gram-positive bacteria, a prevailing hypothesis has been that S. pneumoniae assembles only short pseudopili to destabilize the cell wall for DNA entry. We recently identified a micrometer-sized T4P-like pilus on competent pneumococci, which likely serves as initial DNA receptor. A subsequent study, however, visualized a different structure--short, 'plaited' polymers--released in the medium of competent S. pneumoniae. Biochemical observation of concurrent pilin secretion led the authors to propose that the 'plaited' structures correspond to transformation pili acting as peptidoglycan drills that leave DNA entry pores upon secretion. Here we show that the 'plaited' filaments are not related to natural transformation as they are released by non-competent pneumococci, as well as by cells with disrupted pilus biogenesis components. Combining electron microscopy visualization with structural, biochemical and proteomic analyses, we further identify the 'plaited' polymers as spirosomes: macromolecular assemblies of the fermentative acetaldehyde-alcohol dehydrogenase enzyme AdhE that is well conserved in a broad range of Gram-positive and Gram-negative bacteria.
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Affiliation(s)
- Raphaël Laurenceau
- Unité G5 Biologie Structurale de la Sécrétion Bactérienne, Institut Pasteur, Paris, France
- UMR 3528, CNRS, Institut Pasteur, Paris, France
| | - Petya V. Krasteva
- Unité G5 Biologie Structurale de la Sécrétion Bactérienne, Institut Pasteur, Paris, France
- UMR 3528, CNRS, Institut Pasteur, Paris, France
- * E-mail: (PVK); (RF)
| | - Amy Diallo
- Unité G5 Biologie Structurale de la Sécrétion Bactérienne, Institut Pasteur, Paris, France
- UMR 3528, CNRS, Institut Pasteur, Paris, France
| | - Sahra Ouarti
- Unité G5 Biologie Structurale de la Sécrétion Bactérienne, Institut Pasteur, Paris, France
- UMR 3528, CNRS, Institut Pasteur, Paris, France
| | - Magalie Duchateau
- UMR 3528, CNRS, Institut Pasteur, Paris, France
- Spectrométrie de Masse Structurale et Protéomique, Institut Pasteur, Paris, France
- Plate-Forme de Protéomique, Institut Pasteur, Paris, France
| | - Christian Malosse
- UMR 3528, CNRS, Institut Pasteur, Paris, France
- Spectrométrie de Masse Structurale et Protéomique, Institut Pasteur, Paris, France
- Plate-Forme de Protéomique, Institut Pasteur, Paris, France
| | - Julia Chamot-Rooke
- UMR 3528, CNRS, Institut Pasteur, Paris, France
- Spectrométrie de Masse Structurale et Protéomique, Institut Pasteur, Paris, France
- Plate-Forme de Protéomique, Institut Pasteur, Paris, France
| | - Rémi Fronzes
- Unité G5 Biologie Structurale de la Sécrétion Bactérienne, Institut Pasteur, Paris, France
- UMR 3528, CNRS, Institut Pasteur, Paris, France
- * E-mail: (PVK); (RF)
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68
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MemStar: A one-shotEscherichia coli-based approach for high-level bacterial membrane protein production. FEBS Lett 2014; 588:3761-9. [DOI: 10.1016/j.febslet.2014.08.025] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Revised: 08/21/2014] [Accepted: 08/21/2014] [Indexed: 01/22/2023]
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69
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Ariöz C, Götzke H, Lindholm L, Eriksson J, Edwards K, Daley DO, Barth A, Wieslander A. Heterologous overexpression of a monotopic glucosyltransferase (MGS) induces fatty acid remodeling in Escherichia coli membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:1862-70. [PMID: 24726609 DOI: 10.1016/j.bbamem.2014.04.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 03/27/2014] [Accepted: 04/02/2014] [Indexed: 01/14/2023]
Abstract
The membrane protein monoglucosyldiacylglycerol synthase (MGS) from Acholeplasma laidlawii is responsible for the creation of intracellular membranes when overexpressed in Escherichia coli (E. coli). The present study investigates time dependent changes in composition and properties of E. coli membranes during 22h of MGS induction. The lipid/protein ratio increased by 38% in MGS-expressing cells compared to control cells. Time-dependent screening of lipids during this period indicated differences in fatty acid modeling. (1) Unsaturation levels remained constant for MGS cells (~62%) but significantly decreased in control cells (from 61% to 36%). (2) Cyclopropanated fatty acid content was lower in MGS producing cells while control cells had an increased cyclopropanation activity. Among all lipids, phosphatidylethanolamine (PE) was detected to be the most affected species in terms of cyclopropanation. Higher levels of unsaturation, lowered cyclopropanation levels and decreased transcription of the gene for cyclopropane fatty acid synthase (CFA) all indicate the tendency of the MGS protein to force E. coli membranes to alter its usual fatty acid composition.
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Affiliation(s)
- Candan Ariöz
- The Arrhenius Laboratories for Natural Sciences, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden.
| | - Hansjörg Götzke
- The Arrhenius Laboratories for Natural Sciences, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Ljubica Lindholm
- The Arrhenius Laboratories for Natural Sciences, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Jonny Eriksson
- BMC, Department of Chemistry, Uppsala University, SE-751 23 Uppsala, Sweden
| | - Katarina Edwards
- BMC, Department of Chemistry, Uppsala University, SE-751 23 Uppsala, Sweden
| | - Daniel O Daley
- The Arrhenius Laboratories for Natural Sciences, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Andreas Barth
- The Arrhenius Laboratories for Natural Sciences, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Ake Wieslander
- The Arrhenius Laboratories for Natural Sciences, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
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70
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G-protein-coupled receptor expression and purification. Methods Mol Biol 2014. [PMID: 24648094 DOI: 10.1007/978-1-62703-977-2_33] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
G-protein-coupled receptors (GPCRs) are integral proteins of the cell membrane and are directly involved in the regulation of many biological functions and in drug targeting. However, our knowledge of GPCRs' structure and function remains limited. The first bottleneck in GPCR studies is producing sufficient quantities of soluble, functional, and stable receptors. Currently, GPCR production largely depends on the choice of the overexpression host system and the type of detergent used to extract the GPCR from the cell membrane and stabilize the protein outside the membrane bilayer. Here, we present three protocols that we employ in our lab to produce and solubilize stable GPCRs by cell-free in vitro translation systems, HEK cells, and Escherichia coli. Stable receptors can be purified using immunoaffinity chromatography and gel filtration and can be analyzed with standard biophysical techniques and biochemical assays.
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71
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Yang C, Xie H, Zhang JK, Su BL. Anchoring proteins to Escherichia coli cell membranes using hydrophobic anchors derived from a Bacillus subtilis integral membrane protein. Protein Expr Purif 2012; 85:60-5. [DOI: 10.1016/j.pep.2012.06.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Revised: 06/11/2012] [Accepted: 06/20/2012] [Indexed: 12/01/2022]
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72
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Abstract
Membrane proteins (MPs) mediate important physiological processes for the cell via extracellular and intracellular interactions. To better understand the biochemical and structural bases of these interactions, well-characterized preparations of purified MPs are required. This introduction reviews common problems encountered in MP preparation.
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Affiliation(s)
- Mark L Chiu
- Biologics Research, Biotechnology Center of Excellence, Janssen Research & Development, Radnor, Pennsylvania, USA
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73
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Skretas G, Makino T, Varadarajan N, Pogson M, Georgiou G. Multi-copy genes that enhance the yield of mammalian G protein-coupled receptors in Escherichia coli. Metab Eng 2012; 14:591-602. [PMID: 22609824 DOI: 10.1016/j.ymben.2012.05.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Revised: 04/18/2012] [Accepted: 05/07/2012] [Indexed: 01/01/2023]
Abstract
Low yields of recombinant expression represent a major barrier to the physical characterization of membrane proteins. Here, we have identified genes that globally enhance the production of properly folded G protein-coupled receptors (GPCRs) in Escherichia coli. Libraries of bacterial chromosomal fragments were screened using two separate systems that monitor: (i) elevated fluorescence conferred by enhanced expression of GPCR-GFP fusions and (ii) increased binding of fluorescent ligand in cells producing more active receptor. Three multi-copy hits were isolated by both methods: nagD, encoding the ribonucleotide phosphatase NagD; a fragment of nlpD, encoding a truncation of the predicted lipoprotein NlpD, and the three-gene cluster ptsN-yhbJ-npr, encoding three proteins of the nitrogen phosphotransferase system. Expression of these genes resulted in a 3- to 10-fold increase in the yields of different mammalian GPCRs. Our data is consistent with the hypothesis that the expression of these genes may serve to maintain the integrity of the bacterial periplasm and to provide a favorable environment for proper membrane protein folding, possibly by inducing a fine-tuned stress response and/or via modifying the composition of the bacterial cell envelope.
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Affiliation(s)
- Georgios Skretas
- Department of Chemical Engineering, The University of Texas at Austin, Austin, TX 78712, USA
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74
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Isaksson L, Enberg J, Neutze R, Göran Karlsson B, Pedersen A. Expression screening of membrane proteins with cell-free protein synthesis. Protein Expr Purif 2012; 82:218-25. [DOI: 10.1016/j.pep.2012.01.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Revised: 12/22/2011] [Accepted: 01/03/2012] [Indexed: 12/22/2022]
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75
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Expression and purification of recombinant tung tree diacylglycerol acyltransferase 2. Appl Microbiol Biotechnol 2012; 96:711-27. [DOI: 10.1007/s00253-012-3869-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Revised: 12/19/2011] [Accepted: 12/23/2011] [Indexed: 12/11/2022]
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76
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Newly identified genetic variations in common Escherichia coli MG1655 stock cultures. J Bacteriol 2011; 194:303-6. [PMID: 22081388 DOI: 10.1128/jb.06087-11] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have recently identified seven mutations in commonly used stocks of the sequenced Escherichia coli strain MG1655 which do not appear in the reference sequence. The mutations are likely to cause loss of function of the glpR and crl genes, which may have serious implications for physiological experiments using the affected strains.
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