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Alexis E, Schulte CCM, Cardelli L, Papachristodoulou A. Regulation strategies for two-output biomolecular networks. J R Soc Interface 2023; 20:20230174. [PMID: 37528680 PMCID: PMC10394417 DOI: 10.1098/rsif.2023.0174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Accepted: 07/06/2023] [Indexed: 08/03/2023] Open
Abstract
Feedback control theory facilitates the development of self-regulating systems with desired performance which are predictable and insensitive to disturbances. Feedback regulatory topologies are found in many natural systems and have been of key importance in the design of reliable synthetic bio-devices operating in complex biological environments. Here, we study control schemes for biomolecular processes with two outputs of interest, expanding previously described concepts based on single-output systems. Regulation of such processes may unlock new design possibilities but can be challenging due to coupling interactions; also potential disturbances applied on one of the outputs may affect both. We therefore propose architectures for robustly manipulating the ratio/product and linear combinations of the outputs as well as each of the outputs independently. To demonstrate their characteristics, we apply these architectures to a simple process of two mutually activated biomolecular species. We also highlight the potential for experimental implementation by exploring synthetic realizations both in vivo and in vitro. This work presents an important step forward in building bio-devices capable of sophisticated functions.
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Affiliation(s)
- Emmanouil Alexis
- Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, UK
| | - Carolin C. M. Schulte
- Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, UK
- Department of Biology, University of Oxford, Oxford OX1 3RB, UK
| | - Luca Cardelli
- Department of Computer Science, University of Oxford, Oxford OX1 3QD, UK
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2
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Application of Milk Permeate as an Inducer for the Production of Microbial Recombinant Lipolytic Enzymes. FERMENTATION-BASEL 2022. [DOI: 10.3390/fermentation9010027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Recombinantly produced enzymes are applied in many fields, ranging from medicine to food and nutrition, production of detergents, textile, leather, paper, pulp, and plastics. Thus, the cost-effectiveness of recombinant enzyme synthesis is an important issue in biotechnological industry. Isopropyl-β-D-thiogalactoside (IPTG), an analog of lactose, is currently the most widely used chemical agent for the induction of recombinant enzyme synthesis. However, the use of IPTG can lead to production of toxic elements and can introduce physiological stress to cells. Thus, this study aims to find a simpler, cheaper, and safer way to produce recombinant enzymes. In this study, production of several previously designed recombinant lipolytic enzymes (GDEst-95 esterase, GD-95RM lipase, fused GDEst-lip lipolytic enzyme, and putative cutinase Cut+SP from Streptomyces scabiei 87.22) is induced in E. coli BL21 (DE3) using 4 mM milk permeate, a type of waste of the milk manufacturing process possessing >82% lactose. The SDS-PAGE analysis clearly indicates synthesis of all target enzymes during a 2–12 h post-induction timeframe. Further investigation of GDEst-95, GD-95RM, GDEst-lip, and Cut+SP biocatalysts was carried out spectrophotometrically and using zymography method, confirming production of fully active enzymes.
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Pal A, Chaudhuri TK. Enhancement in the production of recombinant human paraoxonase 1 in Escherichia coli: A comprehensive approach of cellular engineering and optimization of protein folding process in vitro. Int J Biol Macromol 2022; 221:1504-1511. [PMID: 36122776 DOI: 10.1016/j.ijbiomac.2022.09.133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Accepted: 09/15/2022] [Indexed: 11/05/2022]
Abstract
Human paraoxonase 1(hPON1) belongs to the paraoxonase (PON) family. It is a calcium-dependent enzyme with a size of ∼43 kDa and is composed of 6 bladed beta-barrel structures with two calcium ions in its active site. In humans, it is synthesized in the liver and remains bound with the high-density lipoproteins (HDL) within the blood. It has immense potential to tackle the poisoning associated with the use of organophosphates (OPs) and their derivatives, such as nerve agents, due to role in their degradation. Therefore, hPON1 serves as a potential bio-scavenger that can be used as an antidote or as a surface decontaminating agent in OPs poisoning. However, present systems prove insufficient to produce it in sufficient quantity to make it industrially relevant. Here, our efforts involve producing it recombinantly in an E. coli system with enhanced expression levels by altering cellular and environmental conditions. This has been further improved by the development of in-vitro refolding process for the denatured recombinant hPON1 (rhPON1) protein. This methodology resulted in approximately 200 mg of the enzymatically functional protein from 1 l of E. coli culture. Proper refolding of rhPON1 was confirmed by comparing its enzymatic activity and conformation with serum purified hPON1.
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Affiliation(s)
- Ankit Pal
- Kusuma School of Biological Sciences, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Tapan K Chaudhuri
- Kusuma School of Biological Sciences, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India.
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Sharma S, Bora RS, Saini KS, Arya R. Optimizing Chaperone Removal Strategy from Overexpressed Recombinant Proteins : GNE, a Case Study. Methods Mol Biol 2022; 2406:339-358. [PMID: 35089567 DOI: 10.1007/978-1-0716-1859-2_20] [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] [Indexed: 06/14/2023]
Abstract
In the last two decades, numerous innovative advances, strategies and protocols have been developed and optimized to improve the quality and quantity of soluble recombinant protein production in E. coli. One of the major challenges being the coelution of chaperone proteins along with desired recombinant protein of interest. The removal of chaperones is important for protein yield, structural determination, optimal activity, and desired function of the recombinant protein. In this chapter, we outline various strategies for removal of chaperone contaminants from oligomeric proteins, with the ultimate objective of ameliorating the quality and proper folding of recombinant proteins. We have discussed in detail the purification and expression of full-length protein, GNE (UDP-N-acetylglucosamine 2-epimerase/ N-acetylmannosamine kinase), as a case study for chaperone removal.
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Affiliation(s)
- Shweta Sharma
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
| | - Roop Singh Bora
- Department of Biotechnology, Eternal University, Baru Sahib, Himachal Pradesh, India
| | - Kulvinder Singh Saini
- Department of Biotechnology, Eternal University, Baru Sahib, Himachal Pradesh, India.
| | - Ranjana Arya
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, India.
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Fatima K, Naqvi F, Younas H. A Review: Molecular Chaperone-mediated Folding, Unfolding and Disaggregation of Expressed Recombinant Proteins. Cell Biochem Biophys 2021; 79:153-174. [PMID: 33634426 DOI: 10.1007/s12013-021-00970-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 02/01/2021] [Indexed: 12/26/2022]
Abstract
The advancements in biotechnology over time have led to an increase in the demand of pure, soluble and functionally active proteins. Recombinant protein production has thus been employed to obtain high expression of purified proteins in bulk. E. coli is considered as the most desirable host for recombinant protein production due to its inexpensive and fast cultivation, simple nutritional requirements and known genetics. Despite all these benefits, recombinant protein production often comes with drawbacks, such as, the most common being the formation of inclusion bodies due to improper protein folding. Consequently, this can lead to the loss of the structure-function relationship of a protein. Apart from various strategies, one major strategy to resolve this issue is the use of molecular chaperones that act as folding modulators for proteins. Molecular chaperones assist newly synthesized, aggregated or misfolded proteins to fold into their native conformations. Chaperones have been widely used to improve the expression of various proteins which are otherwise difficult to produce in E. coli. Here, we discuss the structure, function, and role of major E. coli molecular chaperones in recombinant technology such as trigger factor, GroEL, DnaK and ClpB.
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Affiliation(s)
- Komal Fatima
- Department of Biochemistry, Kinnaird College for Women, Lahore, Punjab, Pakistan
| | - Fatima Naqvi
- Department of Biochemistry, Kinnaird College for Women, Lahore, Punjab, Pakistan
| | - Hooria Younas
- Department of Biochemistry, Kinnaird College for Women, Lahore, Punjab, Pakistan.
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6
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Ahmed N, Afroze B, Abbas R, Khan MA, Akram M, Tahir S, Bakht S, Munir A, Shahid AA. Method for efficient soluble expression and purification of recombinant human interleukin-15. Protein Expr Purif 2020; 177:105746. [PMID: 32916300 DOI: 10.1016/j.pep.2020.105746] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 08/27/2020] [Accepted: 08/30/2020] [Indexed: 11/29/2022]
Abstract
Periplasmic expression of recombinant proteins ensures the production of biologically active proteins in a correctly folded state with several key advantages. This research focused on the in-frame cloning of rhIL-15 in pET-20 (+) vector with pelB-leader sequence to direct the protein to the bacterial periplasm. The target construct periplasmic expression was evaluated in four strains, BL21 (DE3), BL21 (DE3) pLysS, Rosetta 2 (DE3) and Rosetta-gami 2 (DE3). Soluble periplasmic expression of IL-15 was highest in Rosetta-gami 2 (DE3) followed by Rossetta 2 (DE3) whereas negligible expression was observed with rest of two expression host. Best expression clone was selected for purification by dye ligand affinity chromatography. Purified rhIL-15 was characterized by SDS-PAGE, Western blotting and SEC-HPLC. This is the first report of functional recombinant human interleukin-15 being expressed and purified with yield of 120 mg/L in the periplasmic space of E. coli.
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Affiliation(s)
- Nadeem Ahmed
- National Centre of Excellence in Molecular Biology, 87-West Canal, Bank Road, University of the Punjab, Lahore, 53700, Pakistan.
| | - Bakht Afroze
- National Centre of Excellence in Molecular Biology, 87-West Canal, Bank Road, University of the Punjab, Lahore, 53700, Pakistan
| | - Rabia Abbas
- National Centre of Excellence in Molecular Biology, 87-West Canal, Bank Road, University of the Punjab, Lahore, 53700, Pakistan
| | - Mohsin Ahmed Khan
- National Centre of Excellence in Molecular Biology, 87-West Canal, Bank Road, University of the Punjab, Lahore, 53700, Pakistan
| | - Muhammad Akram
- National Centre of Excellence in Molecular Biology, 87-West Canal, Bank Road, University of the Punjab, Lahore, 53700, Pakistan
| | - Saad Tahir
- National Centre of Excellence in Molecular Biology, 87-West Canal, Bank Road, University of the Punjab, Lahore, 53700, Pakistan
| | - Shehman Bakht
- National Centre of Excellence in Molecular Biology, 87-West Canal, Bank Road, University of the Punjab, Lahore, 53700, Pakistan
| | - Ayesha Munir
- National Centre of Excellence in Molecular Biology, 87-West Canal, Bank Road, University of the Punjab, Lahore, 53700, Pakistan
| | - Ahmad Ali Shahid
- National Centre of Excellence in Molecular Biology, 87-West Canal, Bank Road, University of the Punjab, Lahore, 53700, Pakistan
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7
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Soheili S, Jahanian-Najafabadi A, Akbari V. Evaluation of soluble expression of recombinant granulocyte macrophage stimulating factor (rGM-CSF) by three different E. coli strains. Res Pharm Sci 2020; 15:218-225. [PMID: 33088322 PMCID: PMC7540813 DOI: 10.4103/1735-5362.288424] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 03/09/2020] [Accepted: 04/13/2020] [Indexed: 01/08/2023] Open
Abstract
Background and purpose: Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a cytokine with a wide range of therapeutic applications although expression of GM-CSF in Escherichia coli (E. coli) usually leads to formation of insoluble aggregates mostly lack biological activity. The aim of this study was to compare the soluble expression level of GM-CSF in three E. coli strains, BL21 (DE3), SHuffle® T7 and Origami™ 2 (DE3). Experimental approach: The effect of different temperatures and inducer concentrations on soluble expression of GM-CSF was evaluated. The soluble GM-CSF was subjected to endotoxin removal and purification using nickel-nitrilotriacetic acid (Ni-NTA) affinity chromatography, ultrafiltration. The biological activity of produced GM-CSF was evaluated based on its growth promotion effect on TF-1 cell lines by MTT assay method. Findings / Results: A significant improvement of the soluble yield of GM-CSF (about 30% of GM-CSF was expressed as soluble proteins) was observed when protein expression was induced at 30 °C with 0.5 mM isopropyl β- d-1-thiogalactopyranoside (IPTG) in E. coli Shuffle T7. The soluble GM-CSF with a high purity up to 95 % and specific activity of 1.25 × 104 IU/μg was obtained. Conclusion and implications: The proposed strategy here can be used to improve the soluble expression of other hard-to-express proteins with similar structural properties (i.e., containing disulfide binds or cysteine).
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Affiliation(s)
- Sina Soheili
- Department of Pharmaceutical Biotechnology and Isfahan Pharmaceutical Research Center, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, I.R. Iran
| | - Ali Jahanian-Najafabadi
- Department of Pharmaceutical Biotechnology and Isfahan Pharmaceutical Research Center, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, I.R. Iran
| | - Vajihe Akbari
- Department of Pharmaceutical Biotechnology and Isfahan Pharmaceutical Research Center, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, I.R. Iran
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8
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Menacho-Melgar R, Ye Z, Moreb EA, Yang T, Efromson JP, Decker JS, Wang R, Lynch MD. Scalable, two-stage, autoinduction of recombinant protein expression in E. coli utilizing phosphate depletion. Biotechnol Bioeng 2020; 117:2715-2727. [PMID: 32441815 DOI: 10.1002/bit.27440] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 05/19/2020] [Accepted: 05/19/2020] [Indexed: 12/24/2022]
Abstract
We report the scalable production of recombinant proteins in Escherichia coli, reliant on tightly controlled autoinduction, triggered by phosphate depletion in the stationary phase. The method, reliant on engineered strains and plasmids, enables improved protein expression across scales. Expression levels using this approach have reached as high as 55% of the total cellular protein. The initial use of the method in instrumented fed-batch fermentations enables cell densities of ∼30 gCDW/L and protein titers up to 8.1 ± 0.7 g/L (∼270 mg/gCDW). The process has also been adapted to an optimized autoinduction media, enabling routine batch production at culture volumes of 20 μl (384-well plates), 100 μl (96-well plates), 20 ml, and 100 ml. In batch cultures, cell densities routinely reach ∼5-7 gCDW/L, offering protein titers above 2 g/L. The methodology has been validated with a set of diverse heterologous proteins and is of general use for the facile optimization of routine protein expression from high throughput screens to fed-batch fermentation.
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Affiliation(s)
| | - Zhixia Ye
- Department of Biomedical Engineering, Duke University, Durham, North Carolina
| | - Eirik A Moreb
- Department of Biomedical Engineering, Duke University, Durham, North Carolina
| | - Tian Yang
- Department of Biomedical Engineering, Duke University, Durham, North Carolina
| | - John P Efromson
- Department of Biomedical Engineering, Duke University, Durham, North Carolina
| | - John S Decker
- Department of Biomedical Engineering, Duke University, Durham, North Carolina
| | - Ruixin Wang
- Department of Biomedical Engineering, Duke University, Durham, North Carolina
| | - Michael D Lynch
- Department of Biomedical Engineering, Duke University, Durham, North Carolina
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9
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Morales ES, Parcerisa IL, Ceccarelli EA. A novel method for removing contaminant Hsp70 molecular chaperones from recombinant proteins. Protein Sci 2019; 28:800-807. [PMID: 30653276 DOI: 10.1002/pro.3574] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 01/07/2019] [Accepted: 01/08/2019] [Indexed: 11/07/2022]
Abstract
The production of recombinant proteins in bacteria has increased significantly in recent years, becoming a common tool for both research and the industrial production of proteins. One of the requirements of this methodology is to obtain the desired protein without contaminants. However, this goal cannot always be readily achieved. Multiple strategies have been developed to improve the quality of the desired protein product. Nevertheless, contamination with molecular chaperones is one of the recalcitrant problems that still affects the quality of the obtained proteins. The ability of chaperones to bind to unfolded proteins or to regions where the polypeptide chain is exposed make the removal of the contamination during purification challenging to achieve. This work aimed to develop a strategy to remove contaminating DnaK, one of the homologous Hsp70 molecular chaperones found in Escherichia coli, from purified recombinant proteins. For this purpose, we developed a methodology that captures the DnaK from the contaminating proteins by co-incubation with a GST-cleanser protein that has free functional binding sites for the chaperone. The cleanser protein can then be easily removed together with the captured DnaK. Here, we demonstrated the utility of our system by decontaminating a Histidine-tagged recombinant protein in a batch process. The addition of the GST-cleanser protein in the presence of ATP-Mg eliminates the DnaK contamination substantially. Thus, our decontaminant strategy results versatile and straightforward and can be applied to proteins obtained with different expression and purifications systems as well as to small samples or large volume preparations.
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Affiliation(s)
- Enrique S Morales
- Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, 2000, Argentina
| | - Ivana L Parcerisa
- Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, 2000, Argentina
| | - Eduardo A Ceccarelli
- Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, 2000, Argentina
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10
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Mo Q, Fu A, Lin Z, Wang W, Gong L, Li W. Expression and purification of antimicrobial peptide AP2 using SUMO fusion partner technology inEscherichia coli. Lett Appl Microbiol 2018; 67:606-613. [DOI: 10.1111/lam.13079] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 09/11/2018] [Accepted: 09/12/2018] [Indexed: 11/28/2022]
Affiliation(s)
- Q. Mo
- Key Laboratory of Animal Molecular Nutrition of Education of Ministry; College of Animal Sciences, Zhejiang University; Hangzhou China
- College of Biosystems Engineering and Food Science, Zhejiang University; Hangzhou China
| | - A. Fu
- Key Laboratory of Animal Molecular Nutrition of Education of Ministry; College of Animal Sciences, Zhejiang University; Hangzhou China
- Institute of Biology, Westlake Institute for Advanced Study; Westlake University; Hangzhou Zhejiang Province China
| | - Z. Lin
- Key Laboratory of Animal Molecular Nutrition of Education of Ministry; College of Animal Sciences, Zhejiang University; Hangzhou China
| | - W. Wang
- Linyi Institute for Food and Drug Control; Linyi Shandong China
| | - L. Gong
- Key Laboratory of Animal Molecular Nutrition of Education of Ministry; College of Animal Sciences, Zhejiang University; Hangzhou China
| | - W. Li
- Key Laboratory of Animal Molecular Nutrition of Education of Ministry; College of Animal Sciences, Zhejiang University; Hangzhou China
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11
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Hausjell J, Weissensteiner J, Molitor C, Halbwirth H, Spadiut O. E. coli HMS174(DE3) is a sustainable alternative to BL21(DE3). Microb Cell Fact 2018; 17:169. [PMID: 30376846 PMCID: PMC6206895 DOI: 10.1186/s12934-018-1016-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2018] [Accepted: 10/24/2018] [Indexed: 02/07/2023] Open
Abstract
Background Escherichia coli is one of the most widely used hosts for recombinant protein production in academia and industry. Strain BL21(DE3) is frequently employed due to its advantageous feature of lacking proteases which avoids degradation of target protein. Usually it is used in combination with the T7-pET system where induction is performed by one point addition of IPTG. We recently published a few studies regarding lactose induction in BL21(DE3) strains. BL21(DE3) can only take up the glucose-part of the disaccharide when fed with lactose. However, initially additional glucose has to be supplied as otherwise the ATP-related lactose uptake barely happens. Yet, as lactose is an inexpensive compound compared to glucose and IPTG, a new induction strategy by a lactose-only feed during induction seems attractive. Thus, we investigated this idea in the galactose metabolizing strain HMS174(DE3). Results We show that strain HMS174(DE3) can be cultivated on lactose as sole carbon source during induction. We demonstrate that strain HMS174(DE3) exhibits higher product and biomass yields compared to BL21(DE3) when cultivated in a lactose fed-batch. More importantly, HMS174(DE3) cultivated on lactose even expresses more product than BL21(DE3) in a standard IPTG induced glucose fed-batch at the same growth rate. Finally, we demonstrate that productivity in HMS174(DE3) lactose-fed batch cultivations can easily be influenced by the specific lactose uptake rate (qs,lac). This is shown for two model proteins, one expressed in soluble form and one as inclusion body. Conclusions As strain HMS174(DE3) expresses even slightly higher amounts of target protein in a lactose fed-batch than BL21(DE3) in a standard cultivation, it seems a striking alternative for recombinant protein production. Especially for large scale production of industrial enzymes cheap substrates are essential. Besides cost factors, the strategy allows straight forward adjustment of specific product titers by variation of the lactose feed rate. Electronic supplementary material The online version of this article (10.1186/s12934-018-1016-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Johanna Hausjell
- Research Division Biochemical Engineering, Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Vienna, Austria
| | - Julia Weissensteiner
- Research Division Biochemical Engineering, Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Vienna, Austria
| | - Christian Molitor
- Research Division Biochemical Engineering, Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Vienna, Austria
| | - Heidi Halbwirth
- Research Division Biochemical Engineering, Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Vienna, Austria
| | - Oliver Spadiut
- Research Division Biochemical Engineering, Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Vienna, Austria.
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12
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Perrault syndrome type 3 caused by diverse molecular defects in CLPP. Sci Rep 2018; 8:12862. [PMID: 30150665 PMCID: PMC6110781 DOI: 10.1038/s41598-018-30311-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 07/25/2018] [Indexed: 02/02/2023] Open
Abstract
The maintenance of mitochondrial protein homeostasis (proteostasis) is crucial for correct cellular function. Recently, several mutations in the mitochondrial protease CLPP have been identified in patients with Perrault syndrome 3 (PRLTS3). These mutations can be arranged into two groups, those that cluster near the docking site (hydrophobic pocket, Hp) for the cognate unfoldase CLPX (i.e. T145P and C147S) and those that are adjacent to the active site of the peptidase (i.e. Y229D). Here we report the biochemical consequence of mutations in both regions. The Y229D mutant not only inhibited CLPP-peptidase activity, but unexpectedly also prevented CLPX-docking, thereby blocking the turnover of both peptide and protein substrates. In contrast, Hp mutations cause a range of biochemical defects in CLPP, from no observable change to CLPP activity for the C147S mutant, to dramatic disruption of most activities for the “gain-of-function” mutant T145P - including loss of oligomeric assembly and enhanced peptidase activity.
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13
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Efficient genetic approaches for improvement of plasmid based expression of recombinant protein in Escherichia coli : A review. Process Biochem 2017. [DOI: 10.1016/j.procbio.2017.01.026] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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14
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Monk JM, Koza A, Campodonico MA, Machado D, Seoane JM, Palsson BO, Herrgård MJ, Feist AM. Multi-omics Quantification of Species Variation of Escherichia coli Links Molecular Features with Strain Phenotypes. Cell Syst 2016; 3:238-251.e12. [PMID: 27667363 DOI: 10.1016/j.cels.2016.08.013] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Revised: 03/25/2016] [Accepted: 08/19/2016] [Indexed: 11/16/2022]
Abstract
Escherichia coli strains are widely used in academic research and biotechnology. New technologies for quantifying strain-specific differences and their underlying contributing factors promise greater understanding of how these differences significantly impact physiology, synthetic biology, metabolic engineering, and process design. Here, we quantified strain-specific differences in seven widely used strains of E. coli (BL21, C, Crooks, DH5a, K-12 MG1655, K-12 W3110, and W) using genomics, phenomics, transcriptomics, and genome-scale modeling. Metabolic physiology and gene expression varied widely with downstream implications for productivity, product yield, and titer. These differences could be linked to differential regulatory structure. Analyzing high-flux reactions and expression of encoding genes resulted in a correlated and quantitative link between these sets, with strain-specific caveats. Integrated modeling revealed that certain strains are better suited to produce given compounds or express desired constructs considering native expression states of pathways that enable high-production phenotypes. This study yields a framework for quantitatively comparing strains in a species with implications for strain selection.
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Affiliation(s)
- Jonathan M Monk
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Anna Koza
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2970 Hørsholm, Denmark
| | - Miguel A Campodonico
- Department of Bioengineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0412, USA; Centre for Biotechnology and Bioengineering, CeBiB, University of Chile, Beauchef 850, Santiago, Chile
| | - Daniel Machado
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2970 Hørsholm, Denmark
| | - Jose Miguel Seoane
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2970 Hørsholm, Denmark
| | - Bernhard O Palsson
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2970 Hørsholm, Denmark; Department of Bioengineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0412, USA
| | - Markus J Herrgård
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2970 Hørsholm, Denmark
| | - Adam M Feist
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2970 Hørsholm, Denmark; Department of Bioengineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0412, USA.
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15
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Use of a Chimeric Hsp70 to Enhance the Quality of Recombinant Plasmodium falciparum S-Adenosylmethionine Decarboxylase Protein Produced in Escherichia coli. PLoS One 2016; 11:e0152626. [PMID: 27031344 PMCID: PMC4816425 DOI: 10.1371/journal.pone.0152626] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Accepted: 03/16/2016] [Indexed: 01/22/2023] Open
Abstract
S-adenosylmethionine decarboxylase (PfAdoMetDC) from Plasmodium falciparum is a prospective antimalarial drug target. The production of recombinant PfAdoMetDC for biochemical validation as a drug target is important. The production of PfAdoMetDC in Escherichia coli has been reported to result in unsatisfactory yields and poor quality product. The co-expression of recombinant proteins with molecular chaperones has been proposed as one way to improve the production of the former in E. coli. E. coli heat shock proteins DnaK, GroEL-GroES and DnaJ have previously been used to enhance production of some recombinant proteins. However, the outcomes were inconsistent. An Hsp70 chimeric protein, KPf, which is made up of the ATPase domain of E. coli DnaK and the substrate binding domain of P. falciparum Hsp70 (PfHsp70) has been previously shown to exhibit chaperone function when it was expressed in E. coli cells whose resident Hsp70 (DnaK) function was impaired. We proposed that because of its domain constitution, KPf would most likely be recognised by E. coli Hsp70 co-chaperones. Furthermore, because it possesses a substrate binding domain of plasmodial origin, KPf would be primed to recognise recombinant PfAdoMetDC expressed in E. coli. First, using site-directed mutagenesis, followed by complementation assays, we established that KPf with a mutation in the hydrophobic residue located in its substrate binding cavity was functionally compromised. We further co-expressed PfAdoMetDC with KPf, PfHsp70 and DnaK in E. coli cells either in the absence or presence of over-expressed GroEL-GroES chaperonin. The folded and functional status of the produced PfAdoMetDC was assessed using limited proteolysis and enzyme assays. PfAdoMetDC co-expressed with KPf and PfHsp70 exhibited improved activity compared to protein co-expressed with over-expressed DnaK. Our findings suggest that chimeric KPf may be an ideal Hsp70 co-expression partner for the production of recombinant plasmodial proteins in E. coli.
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Balmayor ER. Targeted delivery as key for the success of small osteoinductive molecules. Adv Drug Deliv Rev 2015; 94:13-27. [PMID: 25959428 DOI: 10.1016/j.addr.2015.04.022] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 04/20/2015] [Accepted: 04/29/2015] [Indexed: 02/08/2023]
Abstract
Molecules such as growth factors, peptides and small molecules can guide cellular behavior and are thus important for tissue engineering. They are rapidly emerging as promising compounds for the regeneration of tissues of the musculoskeletal system. Growth factors have disadvantages such as high cost, short half-life, supraphysiological amounts needed, etc. Therefore, small molecules may be an alternative. These molecules have been discovered using high throughput screening. Small osteoinductive molecules exhibit several advantages over growth factors owing to their small sizes, such as high stability and non-immunogenicity. These molecules may stimulate directly signaling pathways that are important for osteogenesis. However, systemic application doesn't induce osteogenesis in most cases. Therefore, local administration is needed. This may be achieved by using a bone graft material providing additional osteoconductive properties. These graft materials can also act by themselves as a delivery matrix for targeted and local delivery. Furthermore, vascularization is necessary in the process of osteogenesis. Many of the small molecules are also capable of promoting vascularization of the tissue to be regenerated. Thus, in this review, special attention is given to molecules that are capable of inducing both angiogenesis and osteogenesis simultaneously. Finally, more recent preclinical and clinical uses in bone regeneration of those molecules are described, highlighting the needs for the clinical translation of these promising compounds.
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Wang J, Pareja KA, Kaiser CA, Sevier CS. Redox signaling via the molecular chaperone BiP protects cells against endoplasmic reticulum-derived oxidative stress. eLife 2014; 3:e03496. [PMID: 25053742 PMCID: PMC4132286 DOI: 10.7554/elife.03496] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Oxidative protein folding in the endoplasmic reticulum (ER) has emerged as a potentially significant source of cellular reactive oxygen species (ROS). Recent studies suggest that levels of ROS generated as a byproduct of oxidative folding rival those produced by mitochondrial respiration. Mechanisms that protect cells against oxidant accumulation within the ER have begun to be elucidated yet many questions still remain regarding how cells prevent oxidant-induced damage from ER folding events. Here we report a new role for a central well-characterized player in ER homeostasis as a direct sensor of ER redox imbalance. Specifically we show that a conserved cysteine in the lumenal chaperone BiP is susceptible to oxidation by peroxide, and we demonstrate that oxidation of this conserved cysteine disrupts BiP's ATPase cycle. We propose that alteration of BiP activity upon oxidation helps cells cope with disruption to oxidative folding within the ER during oxidative stress. DOI:http://dx.doi.org/10.7554/eLife.03496.001 The endoplasmic reticulum is the cellular compartment where approximately one third of the cell's proteins are made. Inside, chaperone molecules bind to newly made protein chains and help them to fold into the three-dimensional structure required for the protein to work correctly. A chaperone called Ero1 helps to facilitate this folding process by catalyzing a reaction that forms strong chemical bonds, which help stabilize the final protein structures. However, this help from Ero1 comes at a cost: forming a stabilizing bond this way also produces a peroxide molecule as a byproduct. Peroxide is a ‘reactive oxygen species’: a chemical that can oxidize and damage proteins and DNA, which can potentially kill the cell. Three other enzymes in the endoplasmic reticulum can convert peroxide into water, to protect the cells from reactive oxygen species build-up. However, not all cells that use Ero1 have these other enzymes, suggesting that other pathways must exist to manage reactive oxygen species. Wang et al. took advantage of yeast cells containing a hyperactive mutant version of the Ero1 enzyme to look for alternative detoxifying mechanisms that occur when the cell is stressed by an excess of reactive oxygen species. In these cells, Wang et al. observed that the high levels of reactive oxygen species caused part of a chaperone molecule called BiP to oxidize. This modification of BiP acts like a switch that the reactive oxygen species flip on. When activated by the reactive oxygen species, BiP enhances its activity as a folding molecular chaperone, keeping proteins apart. This is thought to allow BiP to minimize the protein misfolding that may otherwise occur in the wake of the damage caused by the building levels of peroxide. Wang et al. created a mutant BiP chaperone that mimics the oxidized form, and found that it also protects cells from the damage inflicted by the excess of reactive oxygen species. Wang et al. propose that the BiP chaperone may be an important sensor of reactive oxygen species that changes its activity when these harmful chemicals are present and helps to protect the cell from damage. The success in mimicking the protective effects of oxidized BiP with a mutant BiP suggest that in the future one may be able to design small molecule drugs that bind to BiP to produce the activity of the modified form. DOI:http://dx.doi.org/10.7554/eLife.03496.002
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Affiliation(s)
- Jie Wang
- Department of Molecular Medicine, Cornell University, Ithaca, United States
| | - Kristeen A Pareja
- Department of Molecular Medicine, Cornell University, Ithaca, United States
| | - Chris A Kaiser
- Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
| | - Carolyn S Sevier
- Department of Molecular Medicine, Cornell University, Ithaca, United States
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Structural and functional characterization of an orphan ATP-binding cassette ATPase involved in manganese utilization and tolerance in Leptospira spp. J Bacteriol 2013; 195:5583-91. [PMID: 24123817 DOI: 10.1128/jb.00915-13] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Pathogenic Leptospira species are the etiological agents of the widespread zoonotic disease leptospirosis. Most organisms, including Leptospira, require divalent cations for proper growth, but because of their high reactivity, these metals are toxic at high concentrations. Therefore, bacteria have acquired strategies to maintain metal homeostasis, such as metal import and efflux. By screening Leptospira biflexa transposon mutants for their ability to use Mn(2+), we have identified a gene encoding a putative orphan ATP-binding cassette (ABC) ATPase of unknown function. Inactivation of this gene in both L. biflexa and L. interrogans strains led to mutants unable to grow in medium in which iron was replaced by Mn(2+), suggesting an involvement of this ABC ATPase in divalent cation uptake. A mutation in this ATPase-coding gene increased susceptibility to Mn(2+) toxicity. Recombinant ABC ATPase of the pathogen L. interrogans exhibited Mg(2+)-dependent ATPase activity involving a P-loop motif. The structure of this ATPase was solved from a crystal containing two monomers in the asymmetric unit. Each monomer adopted a canonical two-subdomain organization of the ABC ATPase fold with an α/β subdomain containing the Walker motifs and an α subdomain containing the ABC signature motif (LSSGE). The two monomers were arranged in a head-to-tail orientation, forming a V-shaped particle with all the conserved ABC motifs at the dimer interface, similar to functional ABC ATPases. These results provide the first structural and functional characterization of a leptospiral ABC ATPase.
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Kopanic JL, Al-Mugotir M, Zach S, Das S, Grosely R, Sorgen PL. An Escherichia coli strain for expression of the connexin45 carboxyl terminus attached to the 4th transmembrane domain. Front Pharmacol 2013; 4:106. [PMID: 23986705 PMCID: PMC3750199 DOI: 10.3389/fphar.2013.00106] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 08/07/2013] [Indexed: 11/26/2022] Open
Abstract
A major problem for structural characterization of membrane proteins, such as connexins, by nuclear magnetic resonance (NMR) occurs at the initial step of the process, the production of sufficient amounts of protein. This occurs because proteins must be expressed in minimal based media. Here, we describe an expression system for membrane proteins that significantly improves yield by addressing two common problems, cell toxicity caused by protein translation and codon bias between genomes. This work provides researchers with a cost-effective tool for NMR and other biophysical studies, to use when faced with little-to-no expression of eukaryotic membrane proteins in Escherichia coli expression systems.
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Affiliation(s)
- Jennifer L Kopanic
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center Omaha, NE, USA
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Lo KWH, Ashe KM, Kan HM, Laurencin CT. The role of small molecules in musculoskeletal regeneration. Regen Med 2013; 7:535-49. [PMID: 22817627 DOI: 10.2217/rme.12.33] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The uses of bone morphogenetic proteins and parathyroid hormone therapeutics are fraught with several fundamental problems, such as cost, protein stability, immunogenicity, contamination and supraphysiological dosage. These downsides may effectively limit their more universal use. Therefore, there is a clear need for alternative forms of biofactors to obviate the drawbacks of protein-based inductive factors for bone repair and regeneration. Our group has studied small molecules with the capacity to regulate osteoblast differentiation and mineralization because their inherent physical properties minimize limitations observed in protein growth factors. For instance, in general, small molecule inducers are usually more stable, highly soluble, nonimmunogenic, more affordable and require lower dosages. Small molecules with the ability to induce osteoblastic differentiation may represent the next generation of bone regenerative medicine. This review describes efforts to develop small molecule-based biofactors for induction, paying specific attention to their novel roles in bone regeneration.
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Affiliation(s)
- Kevin W-H Lo
- Institute for Regenerative Engineering, University of Connecticut Health Center, School of Medicine, Farmington, CT 06030, USA
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Ma LS, Narberhaus F, Lai EM. IcmF family protein TssM exhibits ATPase activity and energizes type VI secretion. J Biol Chem 2012; 287:15610-21. [PMID: 22393043 PMCID: PMC3346141 DOI: 10.1074/jbc.m111.301630] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The type VI secretion system (T6SS) with diversified functions is widely distributed in pathogenic Proteobacteria. The IcmF (intracellular multiplication protein F) family protein TssM is a conserved T6SS inner membrane protein. Despite the conservation of its Walker A nucleotide-binding motif, the NTPase activity of TssM and its role in T6SS remain obscure. In this study, we characterized TssM in the plant pathogen Agrobacterium tumefaciens and provided the first biochemical evidence for TssM exhibiting ATPase activity to power the secretion of the T6SS hallmark protein, hemolysin-coregulated protein (Hcp). Amino acid substitutions in the Walker A motif of TssM caused reduced ATP binding and hydrolysis activity. Importantly, we discovered the Walker B motif of TssM and demonstrated that it is critical for ATP hydrolysis activity. Protein-protein interaction studies and protease susceptibility assays indicated that TssM undergoes an ATP binding-induced conformational change and that subsequent ATP hydrolysis is crucial for recruiting Hcp to interact with the periplasmic domain of the TssM-interacting protein TssL (an IcmH/DotU family protein) into a ternary complex and mediating Hcp secretion. Our findings strongly argue that TssM functions as a T6SS energizer to recruit Hcp into the TssM-TssL inner membrane complex prior to Hcp secretion across the outer membrane.
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Affiliation(s)
- Lay-Sun Ma
- Institute of Plant and Microbial Biology and the Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, Academia Sinica, Taipei 11529, Taiwan
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Sharma AK, Mahalik S, Ghosh C, Singh AB, Mukherjee KJ. Comparative transcriptomic profile analysis of fed-batch cultures expressing different recombinant proteins in Escherichia coli. AMB Express 2011; 1:33. [PMID: 22018139 PMCID: PMC3214799 DOI: 10.1186/2191-0855-1-33] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2011] [Accepted: 10/22/2011] [Indexed: 11/12/2022] Open
Abstract
There is a need to elucidate the product specific features of the metabolic stress response of the host cell to the induction of recombinant protein synthesis. For this, the method of choice is transcriptomic profiling which provides a better insight into the changes taking place in complex global metabolic networks. The transcriptomic profiles of three fed-batch cultures expressing different proteins viz. recombinant human interferon-beta (rhIFN-β), Xylanase and Green Fluorescence Protein (GFP) were compared post induction. We observed a depression in the nutrient uptake and utilization pathways, which was common for all the three expressed proteins. Thus glycerol transporters and genes involved in ATP synthesis as well as aerobic respiration were severely down-regulated. On the other hand the amino acid uptake and biosynthesis genes were significantly repressed only when soluble proteins were expressed under different promoters, but not when the product was expressed as an inclusion body (IB). High level expression under the T7 promoter (rhIFN-β and xylanase) triggered the cellular degradation machinery like the osmoprotectants, proteases and mRNA degradation genes which were highly up-regulated, while this trend was not true with GFP expression under the comparatively weaker ara promoter. The design of a better host platform for recombinant protein production thus needs to take into account the specific nature of the cellular response to protein expression.
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Morozova AV, Khaitlina SY, Malinin AY. Heat shock protein DnaK--substrate of actin-specific bacterial protease ECP32. BIOCHEMISTRY (MOSCOW) 2011; 76:455-61. [PMID: 21585321 DOI: 10.1134/s0006297911040080] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
It has been found that actin-specific bacterial protease ECP32 cleaves prokaryotic heat shock protein DnaK, which belongs to the family of heat shock proteins with molecular weight 70 kDa. We propose a new one-step method for DnaK purification using heat treatment. The technique yields ~1 mg of partially purified DnaK from 25 g of wet bacterial biomass. Polyclonal antibodies against DnaK were obtained. The degree of ECP32 catalyzed proteolysis of partially purified DnaK and that of DnaK in initial cell extracts was compared.
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Affiliation(s)
- A V Morozova
- Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia.
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Salunkhe SS, Raiker VA, Rewanwar S, Kotwal P, Kumar A, Padmanabhan S. Enhanced fluorescent properties of an OmpT site deleted mutant of green fluorescent protein. Microb Cell Fact 2010; 9:26. [PMID: 20429908 PMCID: PMC2868801 DOI: 10.1186/1475-2859-9-26] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2010] [Accepted: 04/29/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The green fluorescent protein has revolutionized many areas of cell biology and biotechnology since it is widely used in determining gene expression and for localization of protein expression. Expression of recombinant GFP in E. coli K12 host from pBAD24M-GFP construct upon arabinose induction was significantly lower than that seen in E. coli B cells with higher expression at 30 degrees C as compared to 37 degrees C in E. coli K12 hosts. Since OmpT levels are higher at 37 degrees C than at 30 degrees C, it prompted us to modify the OmpT proteolytic sites of GFP and examine such an effect on GFP expression and fluorescence. Upon modification of one of the two putative OmpT cleavage sites of GFP, we observed several folds enhanced fluorescence of GFP as compared to unmodified GFPuv (Wild Type-WT). The western blot studies of the WT and the SDM II GFP mutant using anti-GFP antibody showed prominent degradation of GFP with negligible degradation in case of SDM II GFP mutant while no such degradation of GFP was seen for both the clones when expressed in BL21 cells. The SDM II GFP mutant also showed enhanced GFP fluorescence in other E. coli K12 OmpT hosts like E. coli JM109 and LE 392 in comparison to WT GFPuv. Inclusion of an OmpT inhibitor, like zinc with WT GFP lysate expressed from an E. coli K12 host was found to reduce degradation of GFP fluorescence by two fold. RESULTS We describe the construction of two GFP variants with modified putative OmpT proteolytic sites by site directed mutagenesis (SDM). Such modified genes upon arabinose induction exhibited varied degrees of GFP fluorescence. While the mutation of K79G/R80A (SDM I) resulted in dramatic loss of fluorescence activity, the modification of K214A/R215A (SDM II) resulted in four fold enhanced fluorescence of GFP. CONCLUSIONS This is the first report on effect of OmpT protease site modification on GFP fluorescence. The wild type and the GFP variants showed similar growth profile in bioreactor studies with similar amounts of recombinant GFP expressed in the soluble fraction of the cell. Our observations on higher levels of fluorescence of SDM II GFP mutant over native GFPuv in an OmpT+ host like DH5alpha, JM109 and LE392 at 37 degrees C reiterates the role played by host OmpT in determining differences in fluorescent property of the expressed GFP. Both the WT GFP and the SDM II GFP plasmids in E. coli BL21 cells showed similar expression levels and similar GFP fluorescent activity at 37 degrees C. This result substantiates our hypothesis that OmpT protease could be a possible factor responsible for reducing the expression of GFP at 37 degrees C for WT GFP clone in K12 hosts like DH5alpha, JM109, LE 392 since the levels of GFP expression of SDM II clone in such cells at 37 degrees C is higher than that seen with WT GFP clone at the same temperature.
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