Improvement of productivity of active horseradish peroxidase in Escherichia coli by coexpression of Dsb proteins

Heterologous expression of bacterial CotA-laccase, characterization and its application for biodegradation of malachite green

Malachite green (MG) is used as fungicide/parasiticide in aquaculture, its persistence is detrimental as it exhibits carcinogenic effects to aquatic organisms. Bacterial laccase evaluated as the best enzyme at extreme condition for aquatic MG removal. Study aims to increase laccase concentration, CotA-laccase from Bacillus subtilis was cloned and overexpressed in Escherichia coli. Optimal catalysis for purified CotA-laccase were at pH 5.0, 60 °C, and 1 mM of (2,2-azino-di-[3-ethylbenzothiazoline-sulphonate-(6)]) with Km and Kcat 0.087 mM and 37.64 S^-1 respectively. MG biodegradation by CotA-laccase in clam and tilapia pond wastewaters and cytotoxic effect of biodegraded products in grouper fin-1 cells were determined. MG degradation by CotA-laccase was equally efficient, exhibiting upto 90-94% decolorization at freshwater and saline conditions and treated solution was non-toxic to GF-1 cells. Thus, recombinant-CotA-laccase could be an environmentally-friendly enzyme for aquaculture to remove MG, thereby effective to reduce its accumulation in aquatic organisms and ensuring safe aquaculture products.

A general approach to protein folding using thermostable exoshells

In vitro protein folding is a complex process which often results in protein aggregation, low yields and low specific activity. Here we report the use of nanoscale exoshells (tES) to provide complementary nanoenvironments for the folding and release of 12 highly diverse protein substrates ranging from small protein toxins to human albumin, a dimeric protein (alkaline phosphatase), a trimeric ion channel (Omp2a) and the tetrameric tumor suppressor, p53. These proteins represent a unique diversity in size, volume, disulfide linkages, isoelectric point and multi versus monomeric nature of their functional units. Protein encapsulation within tES increased crude soluble yield (3-fold to >100-fold), functional yield (2-fold to >100-fold) and specific activity (3-fold to >100-fold) for all the proteins tested. The average soluble yield was 6.5 mg/100 mg of tES with charge complementation between the tES internal cavity and the protein substrate being the primary determinant of functional folding. Our results confirm the importance of nanoscale electrostatic effects and provide a solution for folding proteins in vitro.

Harnessing the potential of bacterial oxidative folding to aid protein production

Protein folding is central to both biological function and recombinant protein production. In bacterial expression systems, which are easy to use and offer high protein yields, production of the protein of interest in its native fold can be hampered by the limitations of endogenous posttranslational modification systems. Disulfide bond formation, entailing the covalent linkage of proximal cysteine amino acids, is a fundamental posttranslational modification reaction that often underpins protein stability, especially in extracytoplasmic environments. When these bonds are not formed correctly, the yield and activity of the resultant protein are dramatically decreased. Although the mechanism of oxidative protein folding is well understood, unwanted or incorrect disulfide bond formation often presents a stumbling block for the expression of cysteine-containing proteins in bacteria. It is therefore important to consider the biochemistry of prokaryotic disulfide bond formation systems in the context of protein production, in order to take advantage of the full potential of such pathways in biotechnology applications. Here, we provide a critical overview of the use of bacterial oxidative folding in protein production so far, and propose a practical decision-making workflow for exploiting disulfide bond formation for the expression of any given protein of interest.

Translocation from the chloroplast stroma into the thylakoid lumen allows expression of recombinant epidermal growth factor in transplastomic tobacco plants

Chloroplast transformation has many potential advantages for the production of recombinant proteins in plants. However, it has been reported that chloroplast expression of many proteins, such as human epidermal growth factor (hEGF), results hindered by post-transcriptional mechanisms. hEGF degradation has been related to the redox potential of the stroma and protein misfolding. To solve this problem, we proposed the redirection of hEGF into the thylakoid lumen where the environment could improve disulfide bonds formation stabilizing the functional conformation of the protein. We generated transplastomic tobacco plants targeting hEGF protein to the thylakoid lumen by adding a transit peptide (Str). Following this approach, we could detect thylakoid lumen-targeted hEGF by western blotting while stromal accumulation of hEGF remained undetectable. Southern blot analysis confirmed the integration of the transgene through homologous recombination into the plastome. Northern blot analysis showed similar levels of egf transcripts in the EGF and StrEGF lines. These results suggest that higher stability of the hEGF peptide in the thylakoid lumen is the primary cause of the increased accumulation of the recombinant protein observed in StrEGF lines. They also highlight the necessity of exploring different sub-organellar destinations to improve the accumulation levels of a specific recombinant protein in plastids.

Extracellular expression of mutant CotA-laccase SF in Escherichia coli and its degradation of malachite green

In this study, mutant CotA-laccase SF was successfully expressed in Escherichia coli by co-expression with phospholipase C. The optimized extracellular expression of CotA-laccase SF was 1257.22 U/L. Extracellularly expressed CotA-laccase SF exhibits enzymatic properties similar to intracellular CotA-laccase SF. CotA-laccase SF could decolorize malachite green (MG) under neutral and alkaline conditions. The K_m and k_cat values of CotA-laccase SF to MG were 39.6 mM and 18.36 s^-1. LC-MS analysis of degradation products showed that MG was finally transformed into 4-aminobenzophenone and 4-aminophenol by CotA-laccase. The toxicity experiment of garlic root tip cell showed that the toxicity of MG metabolites decreased. In summary, CotA-laccase SF had a good application prospect for degrading malachite green.

A simple, real-time assay of horseradish peroxidase using biolayer interferometry

Horseradish peroxidase (HRP) isoenzyme C1a is one of the most widely used enzymes for various analytical methods in bioscience research and medical fields. In these fields, real-time monitoring of HRP activity is highly desirable because the utility of HRP as a reporter enzyme would be expanded. In this study, we developed a simple assay system enabling real-time monitoring of HRP activity by using biolayer interferometry (BLI). The HRP activity was quantitatively detected on a BLI sensor chip by tracing a binding response of tyramide, a substrate of HRP, onto an immobilized protein. This system could be applied to analyses related to oxidase activity, as well as to the functional analysis of recombinant HRP.

Periplasmic Nanobody-APEX2 Fusions Enable Facile Visualization of Ebola, Marburg, and Mĕnglà virus Nucleoproteins, Alluding to Similar Antigenic Landscapes among Marburgvirus and Dianlovirus

We explore evolved soybean ascorbate peroxidase (APEX2) as a reporter when fused to the C-termini of llama nanobodies (single-domain antibodies, sdAb; variable domains of heavy chain-only antibodies, VHH) targeted to the E. coli periplasm. Periplasmic expression preserves authentic antibody N-termini, intra-domain disulphide bond(s), and capitalizes on efficient haem loading through the porous E. coli outer membrane. Using monomeric and dimeric anti-nucleoprotein (NP) sdAb cross-reactive within the Marburgvirus genus and cross-reactive within the Ebolavirus genus, we show that periplasmic sdAb–APEX2 fusion proteins are easily purified at multi-mg amounts. The fusions were used in Western blotting, ELISA, and microscopy to visualize NPs using colorimetric and fluorescent imaging. Dimeric sdAb–APEX2 fusions were superior at binding NPs from viruses that were evolutionarily distant to that originally used to select the sdAb. Partial conservation of the anti-Marburgvirus sdAb epitope enabled the recognition of a novel NP encoded by the recently discovered Mĕnglà virus genome. Antibody–antigen interactions were rationalized using monovalent nanoluciferase titrations and contact mapping analysis of existing crystal structures, while molecular modelling was used to reveal the potential landscape of the Mĕnglà NP C-terminal domain. The sdAb–APEX2 fusions also enabled live Marburgvirus and Ebolavirus detection 24 h post-infection of Vero E6 cells within a BSL-4 laboratory setting. The simple and inexpensive mining of large amounts of periplasmic sdAb–APEX2 fusion proteins should help advance studies of past, contemporary, and perhaps Filovirus species yet to be discovered.

Metal complexation by histidine-rich peptides confers protective roles against cadmium stress in Escherichia coli as revealed by proteomics analysis

The underlying mechanism and cellular responses of bacteria against toxic cadmium ions is still not fully understood. Herein, Escherichia coli TG1 expressing hexahistidine-green fluorescent protein (His6GFP) and cells expressing polyhistidine-fused to the outer membrane protein A (His-OmpA) were applied as models to investigate roles of cytoplasmic metal complexation and metal chelation at the surface membrane, respectively, upon exposure to cadmium stress. Two-dimensional gel electrophoresis (2-DE) and two-dimensional difference in gel electrophoresis (2D-DIGE) in conjunction with mass spectrometry-based protein identification had successfully revealed the low level expression of antioxidative enzymes and stress-responsive proteins such as manganese-superoxide dismutase (MnSOD; +1.65 fold), alkyl hydroperoxide reductase subunit C (AhpC; +1.03 fold) and DNA starvation/stationary phase protection protein (Dps; −1.02 fold) in cells expressing His6GFP in the presence of 0.2 mM cadmium ions. By contrarily, cadmium exposure led to the up-regulation of MnSOD of up to +7.20 and +3.08 fold in TG1-carrying pUC19 control plasmid and TG1 expressing native GFP, respectively, for defensive purposes against Cd-induced oxidative cell damage. Our findings strongly support the idea that complex formation between cadmium ions and His6GFP could prevent reactive oxygen species (ROS) caused by interaction between Cd²⁺ and electron transport chain. This coincided with the evidence that cells expressing His6GFP could maintain their growth pattern in a similar fashion as that of the control cells even in the presence of harmful cadmium. Interestingly, overexpression of either OmpA or His-OmpA in E. coli cells has also been proven to confer protection against cadmium toxicity as comparable to that observed in cells expressing His6GFP. Blockage of metal uptake as a consequence of anchored polyhistidine residues on surface membrane limited certain amount of cadmium ions in which some portion could pass through and exert their toxic effects to cells as observed by the increased expression of MnSOD of up to +9.91 and +3.31 fold in case of TG1 expressing only OmpA and His-OmpA, respectively. Plausible mechanisms of cellular responses and protein mapping in the presence of cadmium ions were discussed. Taken together, we propose that the intracellular complexation of cadmium ions by metal-binding regions provides more efficiency to cope with cadmium stress than the blockage of metal uptake at the surface membrane. Such findings provide insights into the molecular mechanism and cellular adaptation against cadmium toxicity in bacteria.

High yield production of fungal manganese peroxidases by E. coli through soluble expression, and examination of the activities

Oxidative enzymes of white-rot fungi play a key role in lignin biodegradation. Among those fungus, Ceriporiopsis subvermispora degrades lignin before cellulose in wood; C. subvermispora is the only fungus that secretes all known types of manganese peroxidases (CsMnPs). Utilization of lignin-degrading peroxidases has been limited so far due to the lack of efficient preparation methods and intensive characterization. In this study, we developed a highly efficient method to prepare active CsMnPs through soluble expression by E. coli, which had long been impossible. The genes of MnPs selected from each subfamily were codon-optimized and expressed under the control of a cold shock promoter. A proper level of heme incorporation was achieved by continuous addition of hemin during cultivation. As much as 3 mg of purified MnPs was obtained from 100 mL culture, which is an about 20-fold higher yield than that from inclusion bodies through refolding. Further improvement of the solubility on the expression was achieved by combinatorial coexpression of chaperones. All obtained MnPs had heme-to-protein ratios as high as those of native MnPs. They were all active below pH 5. Our method is applicable to other fungal-secreted enzymes should help the progress of their basic characterization and application for better utilization of woody biomass.

Toward a cell-free hydantoinase process: screening for expression optimization and one-step purification as well as immobilization of hydantoinase and carbamoylase

The hydantoinase process is applied for the industrial synthesis of optically pure amino acids via whole cell biocatalysis, providing a simple and well-established method to obtain the catalyst. Nevertheless, whole cell approaches also bear disadvantages like intracellular degradation reactions, transport limitations as well as low substrate solubility. In this work the hydantoinase and carbamoylase from Arthrobacter crystallopoietes DSM 20117 were investigated with respect to their applicability in a cell-free hydantoinase process. Both enzymes were heterologously expressed in Escherichia coli BL21DE3. Cultivation and induction of the hydantoinase under oxygen deficiency resulted in markedly higher specific activities and a further increase in expression was achieved by codon-optimization. Further expression conditions of the hydantoinase were tested using the microbioreactor system BioLector^®, which showed a positive effect upon the addition of 3% ethanol to the cultivation medium. Additionally, the hydantoinase and carbamoylase were successfully purified by immobilized metal ion affinity using Ni Sepharose beads as well as by functionalized magnetic beads, while the latter method was clearly more effective with respect to recovery and purification factor. Immobilization of both enzymes via functionalized magnetic beads directly from the crude cell extract was successful and resulted in specific activities that turned out to be much higher than those of the purified free enzymes.

Thermostable exoshells fold and stabilize recombinant proteins

The expression and stabilization of recombinant proteins is fundamental to basic and applied biology. Here we have engineered a thermostable protein nanoparticle (tES) to improve both expression and stabilization of recombinant proteins using this technology. tES provides steric accommodation and charge complementation to green fluorescent protein (GFPuv), horseradish peroxidase (HRPc), and Renilla luciferase (rLuc), improving the yields of functional in vitro folding by ~100-fold. Encapsulated enzymes retain the ability to metabolize small-molecule substrates, presumably via four 4.5-nm pores present in the tES shell. GFPuv exhibits no spectral shifts in fluorescence compared to a nonencapsulated control. Thermolabile proteins internalized by tES are resistant to thermal, organic, chaotropic, and proteolytic denaturation and can be released from the tES assembly with mild pH titration followed by proteolysis.

Improving recombinant protein expression and stabilization remains a significant challenge. Here, the authors engineer Archaeoglobus fulgidus ferritin as a thermostable exoshell to provide steric accommodation and charge complementation for recombinant proteins, which can improve yields by 100 fold.

Improvement in the production of the human recombinant enzyme N-acetylgalactosamine-6-sulfatase (rhGALNS) in Escherichia coli using synthetic biology approaches

Previously, we demonstrated production of an active recombinant human N-acetylgalactosamine-6-sulfatase (rhGALNS) enzyme in Escherichia coli as a potential therapeutic alternative for mucopolysaccharidosis IVA. However, most of the rhGALNS produced was present as protein aggregates. Here, several methods were investigated to improve production and activity of rhGALNS. These methods involved the use of physiologically-regulated promoters and alternatives to improve protein folding including global stress responses (osmotic shock), overexpression of native chaperones, and enhancement of cytoplasmic disulfide bond formation. Increase of rhGALNS activity was obtained when a promoter regulated under σ^s was implemented. Additionally, improvements were observed when osmotic shock was applied. Noteworthy, overexpression of chaperones did not have any effect on rhGALNS activity, suggesting that the effect of osmotic shock was probably due to a general stress response and not to the action of an individual chaperone. Finally, it was observed that high concentrations of sucrose in conjunction with the physiological-regulated promoter proU_mod significantly increased the rhGALNS production and activity. Together, these results describe advances in the current knowledge on the production of human recombinant enzymes in a prokaryotic system such as E. coli, and could have a significant impact on the development of enzyme replacement therapies for lysosomal storage diseases.

Improved 1, 2, 4-butanetriol production from an engineered Escherichia coli by co-expression of different chaperone proteins

1, 2, 4-Butanetriol (BT) is a high-value non-natural chemical and has important applications in polymers, medical production and military industry. In the constructed BT biosynthesis pathway from xylose in Escherichia coli, the xylose dehydrogenase (Xdh) and the benzoylformate decarboxylase (MdlC) are heterologous enzymes and the activity of MdlC is the key limiting factor for BT production. In this study, six chaperone protein systems were introduced into the engineered E. coli harboring the recombinant BT pathway. The chaperone GroES-GroEL was beneficial to Xdh activity but had a negative effect on MdlC activity and BT titer. The plasmid pTf16 containing the tig gene (trigger factor) was beneficial to Xdh and MdlC activities and improved the BT titer from 0.42 to 0.56 g/l from 20 g/l xylose. However, co-expression of trigger factor and GroES-GroEL simultaneously reduced the activity of MdlC and had no effect on the BT production. The plasmid pKJE7 harboring dnaK-dnaJ-grpE showed significant negative effects on these enzyme activities and cell growth, leading to completely restrained the BT production. Similarly, co-expression of DnaKJ-GrpPE and GroES-GroEL simultaneously reduced Xdh and MdlC activities and decreased the BT titer by 45.2 %. The BT production of the engineered E. coli harboring pTf16 was further improved to the highest level at 1.01 g/l under pH control (pH 7). This work showed the potential application of chaperone proteins in microorganism engineering to get high production of target compounds as an effective and valuable tool.

Molecular and biochemical characterization of a new thermostable bacterial laccase from Meiothermus ruber DSM 1279

A new bacterial laccase gene (mrlac) fromMeiothermus ruberDSM 1279 was successfully overexpressed to produce a laccase (Mrlac) in soluble form inEscherichia coliduring simultaneous overexpression of a chaperone protein (GroEL/ES).

Ultra-high-throughput screening of an in vitro-synthesized horseradish peroxidase displayed on microbeads using cell sorter

The C1a isoenzyme of horseradish peroxidase (HRP) is an industrially important heme-containing enzyme that utilizes hydrogen peroxide to oxidize a wide variety of inorganic and organic compounds for practical applications, including synthesis of fine chemicals, medical diagnostics, and bioremediation. To develop a ultra-high-throughput screening system for HRP, we successfully produced active HRP in an Escherichia coli cell-free protein synthesis system, by adding disulfide bond isomerase DsbC and optimizing the concentrations of hemin and calcium ions and the temperature. The biosynthesized HRP was fused with a single-chain Cro (scCro) DNA-binding tag at its N-terminal and C-terminal sites. The addition of the scCro-tag at both ends increased the solubility of the protein. Next, HRP and its fusion proteins were successfully synthesized in a water droplet emulsion by using hexadecane as the oil phase and SunSoft No. 818SK as the surfactant. HRP fusion proteins were displayed on microbeads attached with double-stranded DNA (containing the scCro binding sequence) via scCro-DNA interactions. The activities of the immobilized HRP fusion proteins were detected with a tyramide-based fluorogenic assay using flow cytometry. Moreover, a model microbead library containing wild type hrp (WT) and inactive mutant (MUT) genes was screened using fluorescence-activated cell-sorting, thus efficiently enriching the WT gene from the 1:100 (WT:MUT) library. The technique described here could serve as a novel platform for the ultra-high-throughput discovery of more useful HRP mutants and other heme-containing peroxidases.

Cellular disulfide bond formation in bioactive peptides and proteins

Bioactive peptides play important roles in metabolic regulation and modulation and many are used as therapeutics. These peptides often possess disulfide bonds, which are important for their structure, function and stability. A systematic network of enzymes--a disulfide bond generating enzyme, a disulfide bond donor enzyme and a redox cofactor--that function inside the cell dictates the formation and maintenance of disulfide bonds. The main pathways that catalyze disulfide bond formation in peptides and proteins in prokaryotes and eukaryotes are remarkably similar and share several mechanistic features. This review summarizes the formation of disulfide bonds in peptides and proteins by cellular and recombinant machinery.

Coexpression of molecular chaperones to enhance functional expression of anti-BNP scFv in the cytoplasm of Escherichia coli for the detection of B-type natriuretic peptide

Molecular chaperones are a ubiquitous family of cellular proteins that mediate the correct folding of other target polypeptides. In our previous study, the recombinant anti-BNP scFv, which has promising applications for diagnostic, prognostic, and therapeutic monitoring of heart failure, was expressed in the cytoplasm of Escherichia coli. However, when the anti-BNP scFv was expressed, 73.4% of expressed antibodies formed insoluble inclusion bodies. In this study, molecular chaperones were coexpressed with anti-BNP scFv with the goal of improving the production of functional anti-BNP in the cytoplasm of E. coli. Five sets of molecular chaperones were assessed for their effects on the production of active anti-BNP scFv. These sets included the following: trigger factor (TF); groES/groEL; groES/groEL/TF; dnaK/dnaJ/grpE; groES/groEL/dnaK/dnaJ/grpE. Of these chaperones, the coexpression of anti-BNP scFv with the groES/groEL chaperones encoded in plasmid pGro7 exhibited the most efficient functional expression of anti-BNP scFv as an active form. Coexpressed with the groES/groEL chaperones, 64.9% of the total anti-BNP scFv was produced in soluble form, which is 2.4 times higher scFv than that of anti-BNP scFv expressed without molecular chaperones, and the relative binding activity was 1.5-fold higher. The optimal concentration of L-arabinose required for induction of the groES/groEL chaperone set was determined to be 1.0 mM and relative binding activity was 3.5 times higher compared with that of no induction with L-arabinose. In addition, soluble anti-BNP scFv was increased from 11.5 to 31.4 μg/ml with optimized inducer concentration (1.0 mM L-arabinose) for the coexpression of the groES/groEL chaperones. These results demonstrate that the functional expression of anti-BNP scFv can be improved by coexpression of molecular chaperones, as molecular chaperones can identify and help to refold improperly folded anti-BNP scFv.

Side effects of chaperone gene co-expression in recombinant protein production

Insufficient availability of molecular chaperones is observed as a major bottleneck for proper protein folding in recombinant protein production. Therefore, co-production of selected sets of cell chaperones along with foreign polypeptides is a common approach to increase the yield of properly folded, recombinant proteins in bacterial cell factories. However, unbalanced amounts of folding modulators handling folding-reluctant protein species might instead trigger undesired proteolytic activities, detrimental regarding recombinant protein stability, quality and yield. This minireview summarizes the most recent observations of chaperone-linked negative side effects, mostly focusing on DnaK and GroEL sets, when using these proteins as folding assistant agents. These events are discussed in the context of the complexity of the cell quality network and the consequent intricacy of the physiological responses triggered by protein misfolding.

Use of folding modulators to improve heterologous protein production in Escherichia coli

Despite the fundamental importance of E. coli in the manufacture of a wide range of biotechnological and biomedical products, extensive process and/or target optimisation is routinely required in order to achieve functional yields in excess of low mg/l levels. Molecular chaperones and folding catalysts appear to present a panacea for problems of heterologous protein folding in the organism, due largely to their broad substrate range compared with, e.g., protein-specific mutagenesis approaches. Painstaking investigation of chaperone overproduction has, however, met with mixed - and largely unpredictable - results to date. The past 5 years have nevertheless seen an explosion in interest in exploiting the native folding modulators of E. coli, and particularly cocktails thereof, driven largely by the availability of plasmid systems that facilitate simultaneous, non-rational screening of multiple chaperones during recombinant protein expression. As interest in using E. coli to produce recombinant membrane proteins and even glycoproteins grows, approaches to reduce aggregation, delay host cell lysis and optimise expression of difficult-to-express recombinant proteins will become even more critical over the coming years. In this review, we critically evaluate the performance of molecular chaperones and folding catalysts native to E. coli in improving functional production of heterologous proteins in the bacterium and we discuss how they might best be exploited to provide increased amounts of correctly-folded, active protein for biochemical and biophysical studies.

Engineering of cysteine residues leads to improved production of a human dipeptidase enzyme in E. coli

Low yields, poor folding efficiencies and improper disulfide bridge formation limit large-scale production of cysteine-rich proteins in Escherichia coli. Human renal dipeptidase (MDP), the only human beta-lactamase known to date, is a homodimeric enzyme, which contains six cysteine residues per monomer. It hydrolyses penem and carbapenem beta-lactam antibiotics and can cleave dipeptides containing amino acids in both D: - and L: -configurations. In this study, MDP accumulated in inactive form in high molecular weight, disulfide-linked aggregates when produced in the E. coli periplasm. Mutagenesis of Cys361 that mediates dimer formation and Cys93 that is unpaired in the native MDP led to production of soluble recombinant enzyme, with no change in activity compared with the wild-type enzyme. The removal of unpaired or structurally inessential cysteine residues in this manner may allow functional production of many multiply disulfide-linked recombinant proteins in E. coli.

High-yield production of secreted active proteins by the Pseudomonas aeruginosa type III secretion system

The Escherichia coli system is the system of choice for recombinant protein production because it is possible to obtain a high protein yield in inexpensive media. The accumulation of protein in an insoluble form in inclusion bodies remains a major disadvantage. Use of the Pseudomonas aeruginosa type III secretion system can avoid this problem, allowing the production of soluble secreted proteins.

Production of active eukaryotic proteins through bacterial expression systems: a review of the existing biotechnology strategies

Among the various expression systems employed for the over-production of proteins, bacteria still remains the favorite choice of a Protein Biochemist. However, even today, due to the lack of post-translational modification machinery in bacteria, recombinant eukaryotic protein production poses an immense challenge, which invariably leads to the production of biologically in-active protein in this host. A number of techniques are cited in the literature, which describe the conversion of inactive protein, expressed as an insoluble fraction, into a soluble and active form. Overall, we have divided these methods into three major groups: Group-I, where the factors influencing the formation of insoluble fraction are modified through a stringent control of the cellular milieu, thereby leading to the expression of recombinant protein as soluble moiety; Group-II, where protein is refolded from the inclusion bodies and thereby target protein modification is avoided; Group-III, where the target protein is engineered to achieve soluble expression through fusion protein technology. Even within the same family of proteins (e.g., tyrosine kinases), optimization of standard operating protocol (SOP) may still be required for each protein's over-production at a pilot-scale in Escherichia coli. However, once standardized, this procedure can be made amenable to the industrial production for that particular protein with minimum alterations.

Enhancing enzymatic activity of penicillin G acylase by coexpressing pcm gene

Penicillin G acylase (PGA; E.C. 3.5.1.11) is an important enzyme which has broad applications in industries of beta-lactim antibiotics production. In this study, a promising PGA gene from Alcaligenes faecalis (afpga) and another pcm gene encoding protein isoaspartate methyltransferase (PIMT) were constructed into pET43.1a((+)) and pET28a((+)), respectively. The recombinant plasmids pETAFPGA and pETPCM were transformed into the same host cell Escherichia coli BL21 (DE3). Results suggested that the two plasmids could peacefully exist in the host cell and the two genes could be efficiently expressed after induction. The product of pcm gene could function as a helper molecule for enzyme AFPGA. PIMT increased the enzymatic activities in supernatant of ferment broth (1.6 folds) and cell lysate (1.8 folds), while it did not significantly affect the expression level of penicillin G acylase.