Evaluation of pre-induction temperature, cell growth at induction and IPTG concentration on the expression of a leptospiral protein in E. coli using shaking flasks and microbioreactor

Cloning and heterologous expression of Fusarium oxysporum nitrilase gene in Escherichia coli and evaluation in cyanide degradation

Cyanide is widely utilized in the extraction of precious metal extraction even though it has been deemed as the most toxic compound. Fusarium oxysporum has been shown to degrade cyanide through the activity of the Nitrilase enzyme. In this study, the coding sequence of nitrilase gene from F. oxysporum genomic DNA was optimized for cloning and expression in E. coli. The pUC57 containing synthetic optimized nitrilase gene was transferred into E. coli DH5α strain. This nitrilase gene was sub-cloned into pET26b (+) expression vector containing an in-built His-tag at the C-terminal end to facilitate its purification. The recombinant plasmid, pETAM1, was confirmed by PCR, digestion pattern, and sequencing. The recombinant protein was overproduced in E. coli BL21 (DE3). The results of the SDS-PAGE pattern and Western blot analysis confirmed the expression of the expected recombinant protein. For expression optimization of Nitrilase protein, M16 orthogonal experimental design of the Taguchi method was used. The effect of induction time, temperature and IPTG concentration were examined using four levels for each factors. Estimation of the amount of the expressed protein was calculated via densitometry on SDS-PAGE. The enzyme activity and expression in E. coli proved to be successful since there was ammonia production when potassium cyanide and acrylonitrile were used as substrates while the highest enzyme activity of 88% was expressed at 30 °C. The Km and Vm values of the expressed Nitrilase enzyme were determined to be 0.68 mM and 0.48 mM/min respectively.

Elucidating the structure-function attributes of a trypanosomal arginyl-tRNA synthetase

Aminoacyl-tRNA synthetases (aaRSs) are fundamental components of the protein translation machinery. In light of their pivotal role in protein synthesis and structural divergence among species, they have always been considered potential targets for the development of antimicrobial compounds. Arginyl-tRNA synthetase from Trypanosoma cruzi (TcArgRS), the parasite responsible for causing Chagas Disease, contains a 100-amino acid insertion that was found to be completely absent in the human counterpart of similar length, as ascertained from multiple sequence alignment results. Thus, we were prompted to perform a preliminary characterization of TcArgRS using biophysical, biochemical, and bioinformatics tools. We expressed the protein in E. coli and validated its in-vitro enzymatic activity. Additionally, analysis of DTNB kinetics, Circular dichroism (CD) spectra, and ligand-binding studies using intrinsic tryptophan fluorescence measurements aided us to understand some structural features in the absence of available crystal structures. Our study indicates that TcArgRS can discriminate between L-arginine and its analogues. Among the many tested substrates, only L-canavanine and L-thioarginine, a synthetic arginine analogue exhibited notable activation. The binding of various substrates was also determined using in silico methods. This study may provide a viable foundation for studying small compounds that can be targeted against TcArgRS.

Central carbon metabolite profiling reveals vector-associated differences in the recombinant protein production host Escherichia coli BL21

The Gram-negative bacterium Escherichia coli is the most widely used host for recombinant protein production, both as an industrial expression platform and as a model system at laboratory scale. The recombinant protein production industry generates proteins with direct applications as biopharmaceuticals and in technological processes central to a plethora of fields. Despite the increasing economic significance of recombinant protein production, and the importance of E. coli as an expression platform and model organism, only few studies have focused on the central carbon metabolic landscape of E. coli during high-level recombinant protein production. In the present work, we applied four targeted CapIC- and LC-MS/MS methods, covering over 60 metabolites, to perform an in-depth metabolite profiling of the effects of high-level recombinant protein production in strains derived from E. coli BL21, carrying XylS/Pm vectors with different characteristics. The mass-spectrometric central carbon metabolite profiling was complemented with the study of growth kinetics and protein production in batch bioreactors. Our work shows the robustness in E. coli central carbon metabolism when introducing increased plasmid copy number, as well as the greater importance of induction of recombinant protein production as a metabolic challenge, especially when strong promoters are used.

Cloning, improved expression and purification of invasion plasmid antigen D (IpaD): an effector protein of enteroinvasive Escherichia coli (EIEC)

The widespread increase in broad-spectrum antimicrobial resistance is making it more difficult to treat gastrointestinal infections. Enteroinvasive Escherichia coli is a prominent etiological agent of bacillary dysentery, invading via the fecal-oral route and exerting virulence on the host via the type III secretion system. IpaD, a surface-exposed protein on the T3SS tip that is conserved among EIEC and Shigella, may serve as a broad immunogen for bacillary dysentery protection. For the first time, we present an effective framework for improving the expression level and yield of IpaD in the soluble fraction for easy recovery, as well as ideal storage conditions, which may aid in the development of new protein therapies for gastrointestinal infections in the future. To achieve this, uncharacterized full length IpaD gene from EIEC was cloned into pHis-TEV vector and induction parameters were optimized for enhanced expression in the soluble fraction. After affinity-chromatography based purification, 61% pure protein with a yield of 0.33 mg per litre of culture was obtained. The purified IpaD was retained its secondary structure with a prominent α-helical structure as well as functional activity during storage, at 4°C, -20°C and -80°C using 5% sucrose as cryoprotectants, which is a critical criterion for protein-based treatments.

Systems and strategies for plant protein expression

At least a quarter of the protein-encoding genes in plant genomes are predicted to encode enzymes for which no physiological function is known. Determining functions for these uncharacterized enzymes is key to understanding plant metabolism. Functional characterization typically requires expression and purification of recombinant enzymes to be used in enzyme assays and/or for protein structure elucidation studies. Here, we describe several practical considerations used to improve the heterologous expression and purification of Arabidopsis thaliana and Zea mays NAD(P)HX dehydratase (NAXD) and NAD(P)HX epimerase (NAXE), two enzymes that are involved in repair of chemically damaged NAD(P)H cofactors. We provide protocols for transit peptide prediction and construct design, expression in Escherichia coli, and purification of NAXD and NAXE. Many of these strategies are generally applicable to the purification of any plant protein.

Cloning and expression of recombinant human superoxide dismutase 1 (hSOD1) in Bacillus subtilis 1012

OBJECTIVE

We aimed to clone and express the human Cu, Zn superoxide dismutase (hSOD1) in Bacillus subtilis 1012. Also, we investigated the expression level of hSOD1 under different induction conditions.

RESULT

As an essential member of the antioxidant defense system in vivo, hSOD1 has become a therapeutic agent against host diseases, such as oxygen toxicity, acute inflammation, and radiation injury. The recombinant hSOD1 was successfully secreted extracellularly into B. subtilis 1012. The expression conditions were optimized, including inoculum size, different media, temperatures, and inducer concentrations. Finally, the highest level of hSOD1 was produced as a soluble form in Super rich medium by 2% inoculum with 0.2 mM of IPTG at 37 °C after the induction for 24 h. Besides, 20 g/L of lactose also displayed the same inductive effect on hSOD1 expression as that of IPTG (0.2 mM). Finally, the specific activity of purified hSOD1 was determined to be 1625 U/mg in the presence of 800 μM of Cu²⁺ and 20 μM of Zn²⁺.

CONCLUSIONS

We propose that the B. subtilis 1012-hSOD1 strain system has great potential in future industrial applications.

Development of a Single-Chain Variable Fragment of CR3022 for a Plasmonic-Based Biosensor Targeting the SARS-CoV-2 Spike Protein

Two years after SARS-CoV-2 caused the first case of COVID-19, we are now in the "new normal" period, where people's activity has bounced back, followed by the easing of travel policy restrictions. The lesson learned is that the wide availability of accurate and rapid testing procedures is crucial to overcome possible outbreaks in the future. Therefore, many laboratories worldwide have been racing to develop a new point-of-care diagnostic test. To aid continuous innovation, we developed a plasmonic-based biosensor designed explicitly for portable Surface Plasmon Resonance (SPR). In this study, we designed a single chain variable fragment (scFv) from the CR3022 antibody with a particular linker that inserted a cysteine residue at the second position. It caused the linker to have a strong affinity to the gold surface through thiol-coupling and possibly become a ready-to-use bioreceptor toward a portable SPR gold chip without purification steps. The theoretical affinity of this scFv on spike protein was -64.7 kcal/mol, computed using the Molecular Mechanics Generalized Born Surface Area (MM/GBSA) method from the 100 ns molecular dynamics trajectory. Furthermore, the scFv was produced in Escherichia coli BL21 (DE3) as a soluble protein. The binding activity toward Spike Receptor Binding Domain (RBD) SARS-CoV-2 was confirmed with a spot-test, and the experimental binding free energy of -10.82 kcal/mol was determined using portable SPR spectroscopy. We hope this study will be useful in designing specific and low-cost bioreceptors, particularly early in an outbreak when the information on antibody capture is still limited.

A novel sustainable platform for scaled manufacturing of double-stranded RNA biopesticides

RNA interference (RNAi) represents one of the most conserved pathways evolved by eukaryotic cells for regulating gene expression. RNAi utilises non-translatable double-stranded RNA (dsRNA) molecules to sequester or degrade mRNA molecules gene. In RNAi, specifically designed exogenous dsRNA delivered to the cell can silence a target gene, a phenomenon that has been exploited in many functional studies and explored in biopesticide applications. The search for safe and sustainable crop pest management options drives the need to offset the effect of inorganic pesticides on biodiversity. The prospect of replacing inorganic pesticides with dsRNA crop spray is gaining popularity, enhanced by its high-target specificity and low environmental impact. However, for dsRNA to reach the pesticide market, it must be produced cost-effectively and sustainably. In this paper, we develop a high-yield expression media that generates up to 15-fold dsRNA yield compared to existing expression media utilising 1 mM IPTG. We also optimise a low-cost purification method that generates high-quality and purified dsRNA. The developed method circumvents the need for hazardous chemical reagents often found in commercial kits or commercial nucleases to eliminate contaminating DNA or single-stranded RNA (ssRNA) species. We also demonstrate that the production platform is scalable, generating 6.29 mg dsRNA from 259 mg wet E. coli cell pellet. The results also provide structural insights into the heterogeneous dsRNA species within the microbial-derived dsRNA pool. Finally, we also show that the purified 'naked' dsRNA, without prior formulation, can induce insect toxicity under field conditions. This study provides a novel, complete, low-cost process dsRNA platform with potential for application in industrial dsRNA production.

Expression of Codon-Optimized Gene Encoding Murine Moloney Leukemia Virus Reverse Transcriptase in Escherichia coli

Moloney murine leukemia virus reverse transcriptase (MMLV-RT) is the most frequently used enzyme in molecular biology for cDNA synthesis. To date, reverse transcription coupled with Polymerase Chain Reaction, known as RT-PCR, has been popular as an excellent approach for the detection of SARS-CoV-2 during the COVID-19 pandemic. In this study, we aimed to improve the enzymatic production and performance of MMLV-RT by optimizing both codon and culture conditions in E. coli expression system. By applying the optimized codon and culture conditions, the enzyme was successfully overexpressed and increased at high level based on the result of SDS-PAGE and Western blotting. The total amount of MMLV-RT has improved 85-fold from 0.002 g L^-1 to 0.175 g L^-1 of culture. One-step purification by nickel affinity chromatography has been performed to generate the purified enzyme for further analysis of qualitative and quantitative RT activity. Overall, our investigation provides useful strategies to enhance the recombinant enzyme of MMLV-RT in both production and performance. More importantly, the enzyme has shown promising activity to be used for RT-PCR assay.

Analysis and validation of silica-immobilised BST polymerase in loop-mediated isothermal amplification (LAMP) for malaria diagnosis

Bacillus stearothermophilus large fragment (BST_LF) DNA polymerase is reported, isolated on silica via a fused R5 silica-affinity peptide and used in nucleic acid diagnostics. mCherry (mCh), included in the fusion construct, was shown as an efficient fluorescent label to follow the workflow from gene to diagnostic. The R5 immobilisation on silica from cell lysate was consistent with cooperative R5-specific binding of R5₂-mCh-FL-BST_LF or R5₂-mCh-H10-BST_LF fusion proteins followed by non-specific protein binding (including E. coli native proteins). Higher R5-binding could be achieved in the presence of phosphate, but phosphate residue reduced loop-mediated isothermal amplification (LAMP) performance, possibly blocking sites on the BST_LF for binding of β- and γ-phosphates of the dNTPs. Quantitative assessment showed that cations (Mg²⁺ and Mn²⁺) that complex the PPi product optimised enzyme activity. In malaria testing, the limit of detection depended on Plasmodium species and primer set. For example, 1000 copies of P. knowlesi 18S rRNA could be detected with the P.KNO-LAU primer set with Si-R5₂-mCh-FL-BST_LF , but 10 copies of P. ovale 18S rRNA could be detected with the P.OVA-HAN primer set using the same enzyme. The Si-immobilised BST_LF outperformed the commercial enzyme for four of the nine Plasmodium LAMP primer sets tested. Si-R5₂-mCh-FL-BST_LF production was transferred from Cambridge to Accra and set up de novo for a trial with clinical samples. Different detection limits were found, targeting the mitochondrial DNA or the 18S rRNA gene for P. falciparum. The results are discussed in comparison with qPCR and sampling protocol and show that the Si-BST_LF polymerase can be optimised to meet the WHO recommended guidelines.

The DNA polymerase of bacteriophage YerA41 replicates its T-modified DNA in a primer-independent manner

Yersinia phage YerA41 is morphologically similar to jumbo bacteriophages. The isolated genomic material of YerA41 could not be digested by restriction enzymes, and used as a template by conventional DNA polymerases. Nucleoside analysis of the YerA41 genomic material, carried out to find out whether this was due to modified nucleotides, revealed the presence of a ca 1 kDa substitution of thymidine with apparent oligosaccharide character. We identified and purified the phage DNA polymerase (DNAP) that could replicate the YerA41 genomic DNA even without added primers. Cryo-electron microscopy (EM) was used to characterize structural details of the phage particle. The storage capacity of the 131 nm diameter head was calculated to accommodate a significantly longer genome than that of the 145 577 bp genomic DNA of YerA41 determined here. Indeed, cryo-EM revealed, in contrast to the 25 Å in other phages, spacings of 33-36 Å between shells of the genomic material inside YerA41 heads suggesting that the heavily substituted thymidine increases significantly the spacing of the DNA packaged inside the capsid. In conclusion, YerA41 appears to be an unconventional phage that packages thymidine-modified genomic DNA into its capsids along with its own DNAP that has the ability to replicate the genome.

Moniezia benedeni infection enhances neuromedin U (NMU) expression in sheep (Ovis aries) small intestine

BACKGROUND

Neuromedin U (NMU) plays an important role in activating the group 2 innate lymphoid cells (ILC2s) and initiating the host's anti-parasitic immune responses. It is aimed to explore the distribution characteristics of NMU in the sheep small intestine and the influence of Moniezia benedeni infection on them. In the present study, the pET-28a-NMU recombinant plasmids were constructed, and Escherichia coli. BL21 (DE3) were induced to express the recombinant protein. And then, the rabbit anti-sheep NMU polyclonal antibody was prepared and immunofluorescence staining was performed with it. The expression levels of NMU in the intestine of normal and Moniezia benedeni-infected sheep were detected by ELISA.

RESULTS

The results showed that the molecular weight of the obtained NMU recombinant protein was consistent with the expected molecular (13 kDa) and it was expressed in the form of inclusion body. The titer and specificity of obtained rabbit anti-sheep NMU polyclonal antibody were good. The results of immunofluorescence analysis showed that the nerve fibers which specifically expressed NMU mainly extended from the ganglion in the submucosal to lamina propria (LP) in the sheep small intestine, and the expression level was relatively high; especially on the nerve fibers of LP around the intestinal glands. The expression levels were gradually increased from the duodenum to the ileum, and the levels in the jejunum and ileum were significantly higher than that in the duodenum (P < 0.05). In addition, scattered NMU positive cells were distributed in the epithelium of the jejunal crypts. Moniezia benedeni infection increased the expression of NMU in each intestinal segment, especially in the jejunum and ileum there were significant increase (P < 0.05).

CONCLUSIONS

It was suggested that Moniezia benedeni infection could be detected by the high expression of NMU in sheep enteric nervous, and which laid the foundation for further studies on whether NMU exerts anti-parasitic immunity by activating ILC2s. In addition, NMU was expressed in some intestinal gland epitheliums, which also provided a basis for studying its roles in regulation of the immune homeostasis. The present study laid the foundation for further revealing the molecular mechanism of sheep's neural-immune interaction network perceiving the colacobiosis of parasites.

Recombinant Protein Production in E. coli Using the phoA Expression System

Auto-inducible promoter systems have been reported to increase soluble product formation in the periplasm of E. coli compared to inducer-dependent systems. In this study, we investigated the phosphate (PO4)-sensitive phoA expression system (pAT) for the production of a recombinant model antigen-binding fragment (Fab) in the periplasm of E. coli in detail. We explored the impact of non-limiting and limiting PO4 conditions on strain physiology as well as Fab productivity. We compared different methods for extracellular PO4 detection, identifying automated colorimetric measurement to be most suitable for at-line PO4 monitoring. We showed that PO4 limitation boosts phoA-based gene expression, however, the product was already formed at non-limiting PO4 conditions, indicating leaky expression. Furthermore, cultivation under PO4 limitation caused physiological changes ultimately resulting in a metabolic breakdown at PO4 starvation. Finally, we give recommendations for process optimization with the phoA expression system. In summary, our study provides very detailed information on the E. coli phoA expression system, thus extending the existing knowledge of this system, and underlines its high potential for the successful production of periplasmic products in E. coli.

Recombinant HNP-1 Produced by Escherichia coli Triggers Bacterial Apoptosis and Exhibits Antibacterial Activity against Drug-Resistant Bacteria

Human neutrophil peptide-1 (HNP-1) is a promising antibiotic candidate, but its clinical applications have been hampered by challenges during mass production and an inadequate understanding of its bactericidal mechanisms. In this study, we demonstrated that Escherichia coli expressing full-length preproHNP-1 secretes a soluble form of HNP-1, which can be recovered from the total cell lysate after isopropyl thio-β-d-galactoside (IPTG) induction and ultrafiltration. Label-free quantitative proteomics and co-immunoprecipitation experiments revealed that HNP-1 induces cell apoptosis in bacteria by causing DNA and membrane damage. Notably, we found that HNP-1 disrupts the DNA damage response pathway by interfering with the binding of RecA to single-stranded DNA (ssDNA). Further experiments demonstrated that HNP-1 encapsulated in liposomes inhibits the growth of methicillin-resistant Staphylococcus aureus (MRSA) and meropenem-resistant Pseudomonas aeruginosa (MRPA). These results indicated that recombinant protein expression may be a simple and cost-effective solution to produce HNP-1 and that RecA inhibition via HNP-1 may serve as an alternative strategy to counteract antibiotic resistance. IMPORTANCE Human neutrophil peptide-1 (HNP-1) is a promising antibiotic candidate, but its clinical application has been hampered by the difficulty of mass production and an inadequate understanding of its bactericidal mechanisms. In this study, we demonstrated that recombinant protein expression combined with ultrafiltration may be a simple and cost-effective solution to HNP-1 production. We further found that HNP-1 induces bacterial apoptosis and prevents its SOS repair pathway from binding to the RecA protein, which may be a new antibacterial mechanism. In addition, we showed that HNP-1 encapsulated in liposomes inhibits the growth of methicillin-resistant Staphylococcus aureus (MRSA) and meropenem-resistant Pseudomonas aeruginosa (MRPA). These results provide new insights into the production and antibacterial mechanism of HNP-1, both of which may promote its clinical application.

Optimization of an Inclusion Body-Based Production of the Influenza Virus Neuraminidase in Escherichia coli

Neuraminidase (NA), as an important protein of influenza virus, represents a promising target for the development of new antiviral agents for the treatment and prevention of influenza A and B. Bacterial host strain Escherichia coli BL21 (DE3)pLysS containing the NA gene of the H1N1 influenza virus produced this overexpressed enzyme in the insoluble fraction of cells in the form of inclusion bodies. The aim of this work was to investigate the effect of independent variables (propagation time, isopropyl β-d-1-thiogalactopyranoside (IPTG) concentration and expression time) on NA accumulation in inclusion bodies and to optimize these conditions by response surface methodology (RSM). The maximum yield of NA (112.97 ± 2.82 U/g) was achieved under optimal conditions, namely, a propagation time of 7.72 h, IPTG concentration of 1.82 mM and gene expression time of 7.35 h. This study demonstrated that bacterially expressed NA was enzymatically active.

Tricarboxylate Citrate Transporter of an Oleaginous Fungus Mucor circinelloides WJ11: From Function to Structure and Role in Lipid Production

The citrate transporter protein (CTP) plays an important role in citrate efflux from the mitochondrial matrix to cytosol that has great importance in oleaginous fungi. The cytoplasmic citrate produced after citrate efflux serves as the primary carbon source for the triacylglycerol and cholesterol biosynthetic pathways. Because of the CTP's importance, our laboratory has extensively studied its structure/function relationships in Mucor circinelloides to comprehend its molecular mechanism. In the present study, the tricarboxylate citrate transporter (Tct) of M. circinelloides WJ11 has been cloned, overexpressed, purified, kinetically, and structurally characterized. The Tct protein of WJ11 was expressed in Escherichia coli, isolated, and functionally reconstituted in a liposomal system for kinetic studies. Our results showed that Tct has a high affinity for citrate with Km 0.018 mM. Furthermore, the tct overexpression and knockout plasmids were created and transformed into M. circinelloides WJ11. The mitochondria of the tct-overexpressing transformant of M. circinelloides WJ11 showed a 49% increase in citrate efflux, whereas the mitochondria of the tct-knockout transformant showed a 39% decrease in citrate efflux compared to the mitochondria of wild-type WJ11. To elucidate the structure-function relationship of this biologically important transporter a 3D model of the mitochondrial Tct protein was constructed using homology modeling. The overall structure of the protein is V-shaped and its 3D structure is dimeric. The transport stability of the structure was also assessed by molecular dynamics simulation studies. The activity domain was identified to form hydrogen bond and stacking interaction with citrate and malate upon docking. Tricarboxylate citrate transporter has shown high binding energy of −4.87 kcal/mol to citric acid, while −3.80 kcal/mol to malic acid. This is the first report of unraveling the structural characteristics of WJ11 mitochondrial Tct protein and understanding the approach of the transporting toward its substrate. In conclusion, the present findings support our efforts to combine functional and structural data to better understand the Tct of M. circinelloides at the molecular level and its role in lipid accumulation.

Development of an Autoinducible Plasmid for Recombinant Protein Production

BACKGROUND

The production of recombinant proteins in E. coli involves such factors as host strains, expression vectors, culture media, and induction methods. The typical procedure to produce heterologous proteins consists of the following: (1) insertion of the target gene into a suitable vector to construct an overexpression plasmid, (2) transformation of a strain specialized for protein production with the constructed plasmid DNA, (3) growth of the host in a suitable medium and induction of the protein production at a right moment, and (4) further growth to get the maximum yield. There are hurdles involved in each of these steps, and researchers have developed many materials or methods, which often require special recipes or procedures.

OBJECTIVE

To eliminate the special requirements for the recombinant protein production by using readily available materials. Also to save time and effort in the routine protein production work.

METHOD

We started with a vector capable of producing a target protein fused to the C-terminus of the maltose binding protein (MBP). The mCherry (red fluorescent protein) gene was fused to MBP. It acted as a reporter in the initial screening procedure. The original lethal gene (barnase) was replaced with sacB. We chose 3 stationary phase promoters, and made hybrids of them by mixing halves from each one. The T5 promoter was replaced with these stationary phase promoters or their hybrids. The best plasmid was selected by the color intensity of the cell pellet. MBP and GST genes were inserted in place of sacB, and their production yields were compared with the original plasmid in the conventional way of expression.

RESULTS

We constructed an expression plasmid with an autoinducible promoter working in a host that was not specially designed for protein production and in a TB medium which did not contain any secret ingredient, nor was difficult to prepare unlike Studier's defined medium. This plasmid also contains a color indicator which turns red when protein production is successful. We tested our system with the maltose binding protein (MBP) and the glutathione S-transferase (GST), and showed that both proteins were produced to a level comparable to what the commercial medium and/or the specialized strain yielded.

CONCLUSION

We developed a plasmid equipped with an autoinducible promoter, a hybrid of the two promoters which were activated at the stationary phase. This plasmid does not need a special E. coli strain nor a sophisticated nor an expensive medium. It produces an intense red (or pink) color, which can be used as an indicator of a successful production of the target protein and as a predictive measure of the amount of the produced target protein. We speculate that this plasmid will have its greatest advantage when growing cells at low temperatures which would inevitably take a long time.  .

Expression of a Tagless Single-Chain Variable Fragment (scFv) of Anti-TNF-α by a Salt Inducible System and its Purification and Characterization

BACKGROUND

Anti-TNF-α scFv is gaining acceptance as an effective drug for various diseases, such as rheumatoid arthritis and Crohn's disease that involve elevated levels of TNF-α. The single-chain variable fragment (scFv) consists of variable regions of heavy and light chains of monoclonal antibodies (mAb). Due to its smaller size, it curbs the mAb's auto-antibody effects and their limitation of penetration into the tissues during the neutralization of TNF-α.

OBJECTIVE

In this work, a cDNA coding for anti-TNF-α scFv was successfully cloned into a pRSET-B vector and efficiently expressed in an E. coli strain GJ1158, a salt inducible system that uses sodium chloride instead of IPTG as an inducer.

METHODS

The protein was expressed in the form of inclusion bodies (IB), solubilized using urea, and refolded by pulse dilution. Further, the amino acid sequence coverage of scFv was confirmed by ESI-Q-TOF MS/MS and MALDI-TOF. Further studies on scaling up the production of scFv and its application of scFv are being carried out.

RESULTS

The soluble fraction of anti-TNF-α scFv was then purified in a single chromatographic step using CM-Sephadex chromatography, a weak cation exchanger with a yield of 10.3 mg/L. The molecular weight of the scFv was found to be ~ 28 kDa by SDS PAGE, and its presence was confirmed by western blot analysis and mass spectrometry.

CONCLUSION

Anti-TNF-α scFv has been successfully purified in a salt inducible system GJ1158. As per the best of our knowledge, this is the first report of purification of Anti-TNF-α scFv in a salt inducible system from soluble fractions as well as inclusion bodies.

A Reconstructed Common Ancestor of the Fatty Acid Photo-decarboxylase Clade Shows Photo-decarboxylation Activity and Increased Thermostability

Light-dependent enzymes are a rare type of biocatalyst with high potential for research and biotechnology. A recently discovered fatty acid photo-decarboxylase from Chlorella variabilis NC64A (CvFAP) converts fatty acids to the corresponding hydrocarbons only when irradiated with blue light (400 to 520 nm). To expand the available catalytic diversity for fatty acid decarboxylation, we reconstructed possible ancestral decarboxylases from a set of 12 extant sequences that were classified under the fatty acid decarboxylases clade within the glucose-methanol choline (GMC) oxidoreductase family. One of the resurrected enzymes (ANC1) showed activity in the decarboxylation of fatty acids, showing that the clade indeed contains several photo-decarboxylases. ANC1 has a 15 °C higher melting temperature (Tm ) than the extant CvFAP. Its production yielded 12-fold more protein than this wild type decarboxylase, which offers practical advantages for the biochemical investigation of this photoenzyme. Homology modelling revealed amino acid substitutions to more hydrophilic residues at the surface and shorter flexible loops compared to the wild type. Using ancestral sequence reconstruction, we have expanded the existing pool of confirmed fatty acid photo-decarboxylases, providing access to a more robust catalyst for further development via directed evolution.

Gene expression of microbial gelatinase activity for porcine gelatine identification

In order to invent a porcine gelatine detection device using microbial resources, bacterial enzymes with a preference towards porcine gelatine and their candidate genes were evaluated. Five (n = 5) bacterial strains isolated from hot spring water and wet clay, Malaysia were screened for their gelatinase activity. The gelatinase enzyme was extracted and purified using ammonium sulphate precipitation prior to performing gelatinase assay on porcine, bovine and fish gelatine medium substrates. The G2 strain or Enterobacter aerogenes (Strain EA1) was selected for whole genome sequenced after showing a consistent trend of preference towards porcine gelatine. The gelatinase candidate gene gelEA1_9 was cloned and expressed. Based on one-way analysis of variance (ANOVA) with POST-HOC Duncan test (α = 0.05), the final product of gelEA1_9 was identified as a novel gelatinase. This gelatinase presented no significant difference in activity towards porcine gelatine. Hence, the present study demonstrated an enzyme-substrate interaction for porcine gelatine identification.

Statistical optimization of culture conditions for expression of recombinant humanized anti-EpCAM single-chain antibody using response surface methodology

Background and purpose:

The epithelial cell adhesion molecule (EpCAM), is one of the first cancer- associated markers discovered. Its overexpression in cancer stem cells, epithelial tumors, and circulating tumor cells makes this molecule interesting for targeted cancer therapy. So, in recent years scFv fragments have been developed for EpCAM targeting.

Experimental approach:

In this study, an scFv against EpCAM extracellular domain (EpEX) derived from 4D5MOC-B humanized mAb was expressed in Escherichia coli k12 strain, and in order to obtain the optimum culture conditions in chemically defined minimal medium, response surface methodology (RSM) was employed. According to the RSM-CCD method, a total of 30 experiments were designed to investigate the effects of various parameters including isopropyl-b-D-thiogalactopyranoside (IPTG) concentration, cell density before induction, post-induction time, and post-induction temperature on anti EpEX-scFv expression level.

Findings/Results:

At the optimum conditions (induction at cell density 0.8 with 0.8 mM IPTG for 24 h at 37 °C), the recombinant anti EpEX-scFv was produced at a titer of 197.33 μg/mL that was significantly consistent with the prediction of the model.

Conclusion and implication:

The optimized-culture conditions obtained here for efficient production of anti EpEX-scFv in shake flask cultivation on a chemically defined minimal medium could be applied to large- scale fermentation for the anti EpEX-scFv production.

Prostaglandin A1 Decreases the Phosphorylation of Tau by Activating Protein Phosphatase 2A via a Michael Addition Mechanism at Cysteine 377

Prostaglandin (PG) A1 is a metabolic product of cyclooxygenase 2 (COX-2) that is potentially involved in regulating the development and progression of Alzheimer's disease (AD). PGA1 is a cyclopentenone (cy) PG characterized by the presence of a chemically reactive α,β-unsaturated carbonyl. PGA1 is potentially involved in the regulation of multiple biological processes via Michael addition; however, the specific roles of PGA1 in AD remain unclear. Tau^P301S transgenic (Tg) mice were used as in vivo AD models, and neuroblastoma (N) 2a cells were used as an in vitro neuronal model. The PGA1-binding proteins were identified by HPLC-MS-MS after intracerebroventricular injection (i.c.v) of PGA1. Western blotting was used to determine tau phosphorylation in PGA1-treated Tg mice in the absence or in the presence of okadaic acid (OA), an inhibitor of protein phosphatase (PP) 2A. A combination of pull-down assay, immunoprecipitation, western blotting, and HPLC-MS-MS was used to determine that the PP2A scaffold subunit A alpha (PPP2R1A) is activated by the direct binding of PGA1 to cysteine 377. The effect of inhibiting tau hyperphosphorylation was tested in the Morris maze to determine the inhibitory effects of PGA1 on cognitive decline in tau^P301S Tg mice. Incubation with N2a cells, pull-down assay, and mass spectrometry (MS) analysis revealed and indicated that PGA1 binds to more than 1000 proteins; some of these proteins are associated with AD and especially with tauopathies. Moreover, short-term administration of PGA1 in tau^P301S Tg mice significantly decreased tau phosphorylation at Thr181, Ser202, and Ser404 in a dose-dependent manner. This effect was caused by the activation of PPP2R1A in tau^P301S Tg mice. Importantly, PGA1 can form a Michael adduct with cysteine 377 of PPP2R1A, which is critical for the enzymatic activity of PP2A. Long-term treatment of tau^P301S Tg mice with PGA1 activated PP2A and significantly reduced tau phosphorylation resulting in improvements in cognitive decline in tau^P301S Tg mice. Our data provided new insight into the mechanisms of the ameliorating effects of PGA1 on cognitive decline in tau^P301S Tg mice by activating PP2A via a mechanism involving the formation of a Michael adduct with cysteine 377 of PPP2R1A.

Optimization of Culture Conditions for the Efficient Biosynthesis of Trilobatin from Phloretin by Engineered Escherichia coli Harboring the Apple Phloretin-4'-O-glycosyltransferase

Trilobatin, a dihydrochalcone glucoside and natural sweetener, has diverse biological and therapeutic properties. In the present study, we developed a microbial system to produce trilobatin from phloretin using Escherichia coli (E. coli) overexpressing the phloretin-4'-O-glycosyltransferase from Malus x domestica Borkh. Various optimization strategies were employed for the efficient production of trilobatin using a one-factor-at-a-time method. The effect of UDP-glucose supplementation, substrate, and inducer concentrations, time of substrate feeding as well as protein induction, and different culture media combinations were evaluated and optimized to enhance the production of trilobatin. As a result, the highest trilobatin production, 246.83 μM (107.64 mg L-1), was obtained with an LB-TB medium combination, 22 h of induction with 0.1 mM IPTG followed by 4 h of feeding with 250 μM phloretin and without extracellular UDP-glucose supplementation. These results demonstrate the efficient production of trilobatin and constitute a promising foundation for large-scale production of the dihydrochalcone glycosides in engineered E. coli.

Exploiting Single Domain Antibodies as Regulatory Parts to Modulate Monoterpenoid Production in E. coli

Synthetic biology and metabolic engineering offer potentially green and attractive routes to the production of high value compounds. The provision of high-quality parts and pathways is crucial in enabling the biosynthesis of chemicals using synthetic biology. While a number of regulatory parts that provide control at the transcriptional and translational level have been developed, relatively few exist at the protein level. Single domain antibodies (sdAb) such as camelid heavy chain variable fragments (V_HH) possess binding characteristics which could be exploited for their development and use as novel parts for regulating metabolic pathways at the protein level in microbial cell factories. Here, a platform for the use of V_HH as tools in Escherichia coli is developed and subsequently used to modulate linalool production in E. coli. The coproduction of a Design of Experiments (DoE) optimized pBbE8k His₆-V_HHCyDisCo system alongside a heterologous linalool production pathway facilitated the identification of anti-bLinS V_HH that functioned as modulators of bLinS. This resulted in altered product profiles and significant variation in the titers of linalool, geraniol, nerolidol, and indole obtained. The ability to alter the production levels of high value terpenoids, such as linalool, in a tunable manner at the protein level could represent a significant step forward for the development of improved microbial cell factories. This study serves as a proof of principle indicating that V_HH can be used to modulate enzyme activity in engineered pathways within E. coli. Given their almost limitless binding potential, we posit that single domain antibodies could emerge as powerful regulatory parts in synthetic biology applications.

Optimization of the Fermentation Media and Parameters for the Bio-control Potential of Trichoderma longibrachiatum T6 Against Nematodes

The cereal cyst nematode Heterodera avenae is one of the important soil-borne pathogens of cereal crops and causes high yield losses worldwide. Trichoderma spp. formulations are applied as commercial bio-control agents against soil-borne plant pathogens such as H. avenae. However, the relationship between Trichoderma longibrachiatum fermentation parameters and its bio-control potential against H. avenae has not been exclusively established. In the present study, the effect of 10 different fermentation media and conditions on the nematicidal activity of T. longibrachiatum T6 (T6) was evaluated with a single-factor method and a Plackett-Burman design, and the interaction between different fermentation parameters was investigated by a Box-Behnken design. The variables for enhancing the nematicidal activity of T6 culture filtrates were explored and optimized using response surface methodology (RSM). The Minor Medium (MM) plus wheat bran-2 medium was found to be the most effective fermentation medium for T6 culture filtrates against the second stage juveniles (J2s) of H. avenae. The maximum mortality of the J2s was obtained using the T6 culture filtrates under the following fermentation conditions: initial pH 6, 28°C culture temperature, 180 rpm rotating speed, 60 ml of fermentation media, 7 days of incubation time, and 1 ml of inoculation volumes. Among these parameters, the initial pH, inoculation volume, and incubation day were identified as the most significant parameters and critical independent variables for enhancing the nematicidal activity of the T6 culture filtrates. After further optimizations based on statistical predictions, the highest nematicidal activity (92.42%) was obtained with the T6 culture filtrates fermented under an initial pH of 6.06, an inoculation volume of 1.62 ml, and an incubation time of 7.15 days. The nematicidal activity was increased approximately by as high as 1.07% compared with that before optimization. Bio-control efficacy of T6 culture filtrates was 83.88% at the 70th day after wheat seeds sowing in greenhouse experiments. The results from the validation experiments agreed with the model predictions. Our study has improved the bio-control potential of Trichoderma spp. against the plant-parasitic nematodes H. avenae and provided a cost-efficient bio-resource in the future development of novel bio-control agents.

Use of plasmids for expression of proteins from the genus Leishmania in Escherichia coli: current state and perspectives

Leishmaniosis is caused by the protozoa of the genus Leishmania with a wide spectrum of clinical and epidemiological manifestations which are characterized into four clinical groups: cutaneous, mucocutaneous, diffuse cutaneous, and visceral. American visceral leishmaniosis (AVL) or visceral leishmaniosis (VL) has been known as the most severe form of the disease. However, despite the growing number of people exposed to the infection risk and the great effort done by the scientific community worldwide to significantly increase the knowledge about these diseases, there is no vaccine capable of preventing VL in humans. In this short review, we present some of the plasmids used for the expression of recombinant protein by Escherichia coli strains used mainly for the second generation of vaccines for leishmaniosis. It can be emphasized that currently, these vectors and hosts play an important role in developing vaccine strategies against the disease. Indeed, use of the E. coli BL21 (DE) strain is remarkable mainly due to its characteristics for being a stable protein producer as well as the use of histidine tags for antigen purification. KEY POINTS: • Plasmid vectors and E. coli will continue being important for studies about leishmaniosis. • Protein purification exploiting histidine tags is a key technique.

Structural investigation of APRs to improve the solubility of outer membrane protease (PgtE) from Salmonella enterica serotype typhi- A multi-constraint approach

Outer membrane proteins were playing a crucial role on the several functions controlled by cell membranes even though they are not naturally expressed at higher levels. In order to obtain biologically active protein, the denaturation of these inclusion bodies must be optimized using chaotropic agents. Hence, this study focuses on improving the yield of Outer Membrane Protease (PgtE) from Salmonella enterica serotype Typhi (S. Typhi) using chaotropes and additives. Denaturation methods were tried with various pH, detergents, and reducing agents were used to optimize the solubility of PgtE with biologically active form. Due to the aggregation, we failed to achieve the maximum yield of PgtE. Consequently, we predicted 9 Aggregation Prone Regions (APRs) in PgtE, which are mutated by known structural Gatekeepers. We calculated the Aggregation Index (AI) of PgtE with 10 mM of aspartic acid as an additive in optimized buffer. In addition, the mutations at specific positions within the protein structure can act as APRs suppressors without affecting protein stability with CABS flex dynamics. The multiple sequence analysis demonstrate that aspartic acid is appropriate denaturing additive for other Gram-negative pathogens of Omptin family.

Preparation of a novel monoclonal antibody against caprine interleukin-17A and its applications in immunofluorescence and immunohistochemistry assays

BACKGROUND

Interleukin-17 (IL-17), the characteristic cytokine secreted by T helper 17 lymphocytes (Th17 cells), plays a pivotal role in host defense and many inflammatory or autoimmune diseases. The aim of this study was to obtain purified protein caprine IL-17A (cIL-17A) as an antigen for preparing an IL-17A-specific monoclonal antibody (mAb).

RESULTS

The coding sequence (CDS) region of cIL-17A was cloned from the peripheral blood mononuclear cells (PBMCs) of dairy goats and then inserted into the expression vector PET 32a and transformed into competent TransB (DE3) cells. Recombinant fusion protein obtained under optimized conditions was used to immunize BALB/c mice for preparing monoclonal antibodies. Finally, the supernatants of two hybridoma cell lines showing positive reaction with the recombinant fusion protein and negative reaction with fusion tags of PET 32a were collected for western blot, immunofluorescence (IF) and immunohistochemistry (IHC) analysis. Our results showed that the maximum amount of soluble protein could be obtained directly in the supernatant when the recombinant expression cells were induced by isopropyl-β-d-thiogalactoside (IPTG) at a concentration of 0.3 mmol/L at 16 °C for 42 h. Western blot analysis showed that the mAb H8 could recognize the eukaryotically expressed cIL-17A in the supernatant of transfected HEK293T cells. Immunofluorescence and immunohistochemistry assays showed that mAb H8 could strongly recognize both the eukaryotically expressed and natural cIL-17A.

CONCLUSIONS

The monoclonal antibody mAb H8 prepared in this study may be a potential tool for the detection of cIL-17A and beneficial for investigating the pathogenesis of various IL-17-associated diseases.

Evaluation of induction conditions for plasmid pQE-30 stability and 503 antigen of Leishmania i. chagasi expression in E. coli M15

The present study aimed to evaluate the influence of induction conditions (IPTG concentration, temperature, and induction time) on the plasmid pQE-30 stability and 503 antigen expression of Leishmania i. chagasi in Escherichia coli M15. Batch cultures were performed at 37 °C and induced by the addition of different IPTG concentrations (0.01 to 1.5 mM). Subsequently, experiments were carried out at different temperatures (27 to 42 °C), evaluating the influence of induction time (0.5 to 6 h after the start of the culture). The results showed that IPTG toxicity caused a metabolic stress in the cells and, consequently, the microorganism growth reduced. The induction with IPTG may also be associated with the plasmid pQE-30 instability, due to metabolic burden imposed by the recombinant protein expression. The optimal conditions for 503 antigen expression of Leishmania i. chagasi in Escherichia coli M15 were an IPTG concentration of 1.0 mM, temperature of 37 °C, and induction time of 2 h. The maximum antigen concentration obtained was 0.119 ± 0.009 g/L, about seven times higher than the lowest concentration. Therefore, the results showed that 503 antigen can be produced in laboratory; however, it requires more studies to minimize the plasmid instability and improve to industrial scale.

Functional characterization of host toxic EcdB transcription factor protein of echinocandin B biosynthetic gene cluster

The ecdB is a transcription factor, located in the echinocandin B biosynthetic gene cluster of Emericella rugulosa NRRL11440. Here, we validated the ecdB mRNA sequence for functional expression and to explore the role of EcdB protein in the echinocandin B regulation. The sequence alignment study revealed that the ecdB coding sequence was found 75 bp shorter than the reference mRNA sequence. This coding sequence encodes for EcdB protein and comprises three conserved domains; DNA binding domain (DBD), coiled-coil domain, and signature middle homology region. The full-length and DBD (truncated) DNA sequences were expressed in Escherichia coli BL21(DE3) under different tested conditions. The expression of EcdB protein was found to be toxic, which curbs the cell growth. In contrast to truncated protein (GST:EcdB1-54), the full-length (GST:EcdB) protein was expressed at very low titer and not detectable in SDS-PAGE under the varying isopropyl β-d-1-thiogalactopyranoside (IPTG), temperature, and media conditions. However, GST:EcdB1-54 was successfully purified under standard conditions (0.5 mM IPTG at 0.5OD) with 33 kDa expected size. The functionality of GST:EcdB1-54 was attained by electrophoretic mobility shift assay study as a clear band shifting showed with ecdA promoter. Taken together, we conclude that EcdB interacts with the ecdA promoter that reflected to require for echinocandin B regulation.

The Goldilocks Approach: A Review of Employing Design of Experiments in Prokaryotic Recombinant Protein Production

The production of high yields of soluble recombinant protein is one of the main objectives of protein biotechnology. Several factors, such as expression system, vector, host, media composition and induction conditions can influence recombinant protein yield. Identifying the most important factors for optimum protein expression may involve significant investment of time and considerable cost. To address this problem, statistical models such as Design of Experiments (DoE) have been used to optimise recombinant protein production. This review examines the application of DoE in the production of recombinant proteins in prokaryotic expression systems with specific emphasis on media composition and culture conditions. The review examines the most commonly used DoE screening and optimisation designs. It provides examples of DoE applied to optimisation of media and culture conditions.

Identifying Protein Interactions with Histone Peptides Using Bio-layer Interferometry

Histone post-translational modifications (PTMs) regulate numerous cellular processes, including gene transcription, cell division, and DNA damage repair. Most histone PTMs affect the recruitment or exclusion of reader proteins from chromatin. Here, we present a protocol to measure affinity and interaction kinetics between histone peptides and the recombinant protein using Bio-layer interferometry.

Using response surface methodology in combination with Plackett-Burman design for optimization of culture media and extracellular expression of Trichoderma reesei synthetic endoglucanase II in Escherichia coli

Cellulases like endoglucanase II (EGII) from Trichoderma reesei are the industrial enzymes responsible for breakdown of cellulosic materials. Due to its importance for production of eco-friendly commercial products such as alternative biofuels, industrial EGII production and optimization of its production conditions merit consideration. The gene responsible for EGII expression was designed and sub-cloned in to pET26b expression vector and transformed into BL21 (DE3) pLysS cells. Protein expression and purification was followed by a RSM design (20 experiments) to optimize the IPTG Concentration, post induction period and cell density (OD₆₀₀). Thereafter, another RSM design (20 experiments) was performed to find and optimize the most important permeabilizing factors to achieve higher extracellular EGII expression. The EGII expression levels were assessed by Ghose method. The EGII gene was sub-cloned and protein expression and purification were successfully performed. The RSM experiments indicated that 0.331 mM for IPTG Concentration, 10.89 H for post induction period and 3.41 for cell density (OD₆₀₀) were the optimum culture. Glycine (0.99%), Triton X-100 (0.73%) and CaCl₂ (0.232) have been assigned as the most effective membrane permeabalizing factors. Optimization of culture medium components has led to a 3.06 fold increase in extracellular expression of EGII. RSM is an amenable method to optimize the expression of commercially significant enzymes. Our results indicated that optimization of IPTG concentration, post induction period and cell density along with glycine, Triton X-100 and Ca²⁺ concentration could lead to more cost effective industrial production of EGII.

Cloning and high-level expression of Thermus thermophilus RecA in E. coli: purification and novel use in HBV diagnostics

We studied the role of Thermus thermophilus Recombinase A (RecA) in enhancing the PCR signals of DNA viruses such as Hepatitis B virus (HBV). The RecA gene of a thermophilic eubacterial strain, T. thermophilus, was cloned and hyperexpressed in Escherichia coli. The recombinant RecA protein was purified using a single heat treatment step without the use of any chromatography steps, and the purified protein (>95%) was found to be active. The purified RecA could enhance the polymerase chain reaction (PCR) signals of HBV and improve the detection limit of the HBV diagnosis by real time PCR. The yield of recombinant RecA was ∼35mg/L, the highest yield reported for a recombinant RecA to date. RecA can be successfully employed to enhance detection sensitivity for the diagnosis of DNA viruses such as HBV, and this methodology could be particularly useful for clinical samples with HBV viral loads of less than 10IU/mL, which is interesting and novel.

Optimization of expression JTAT protein with emphasis on transformation efficiency and IPTG concentration

One of small accessory genes between pol and env is tat gene encoding TAT protein. This research was aimed to optimize the expression of Jembrana TAT (JTAT) protein with preparing Escherichia coli (E. coli) in advance using adopted methods of M1 (MgCl2 + CaCl2) and M2 (CaCl2 + Glycerol). The best transformation efficiency resulting from a better transformation method was used to subsequent expression of JTAT protein. A synthetic tat gene encoding protein JTAT was previously cloned into pBT-hisC. Concentration of 200; 400; 600 µM IPTG was induced to a small volume culture (200 ml; OD600 = 4), incubated for 3 h. Pellets were harvested by centrifugation (4000 rpm; 4 °C; 15 min). Buffer B (10 mM Immidazole) was added into pellets, lysed by freeze-thaw followed by sonication. Supernatant was collected by centrifugation (10,000 rpm; 4 °C; 20 min) and purified using Ni-NTA Agarose resin, released by elution buffer (E) containing 400 mM Immidazole to collect purified protein twice (E1, E2). The protein was characterized by SDS-PAGE and Western Blot (WB), quantified (at λ595 nm) with BSA standard method in prior. The result showed that transformation efficiency was better in M2 (2.53 × 106) than M1 (3.10 × 105). The JTAT protein was expressed at a right size of 11.8 kDa. Concentration of 200 µM IPTG produced a significantly better protein yield (1.500 ± 0.089 mg/ml; P < 0.05) than 600 µM IPTG (0.896 ± 0.052 mg/ml) and not different to 400 µM IPTG (1.298 ± 0.080 mg/ml). This research indicated that transformation efficiency needs to be taken account in prior of optimization of the protein expression.

Microbial expression of Exendin-4 analog and its efficacy in mice model

Exendin-4 is a GLP 1 agonist incretin-mimetic peptide hormone comprising 39 amino acids. Exenatide (Byetta^®) is a chemically synthesized version of Exendin-4 with an additional C-terminal amidation. Exenatide acts as a GLP-1 receptor agonist. This paper illustrates the method adopted for cloning, fermentation and purification of recombinant Exendin-4 analog expressed in Escherichia coli. The biologically expressed analog was extensively characterized using different orthogonal methods to confirm their biological activity and physicochemical properties. It was observed that the expressed analog showed comparable functional properties as that of Byetta^® irrespective of their modes of development. Further, in vivo efficacy of the recombinant Exendin-4 analog was studied in Oral Glucose Tolerance Test (OGTT) in mice models. Byetta^® and Exendin-4 analog treated groups showed comparable glucose lowering activity in the OGTT model.

A Living Eukaryotic Autocementation Kit from Surface Display of Silica Binding Peptides on Yarrowia lipolytica

With the development of civil engineering, the demand for suitable cementation materials is increasing rapidly. However, traditional cementation methods are not eco-friendly enough and more sustainable approach such as biobased cementation is required. To meet such demand, Euk.cement, a living eukaryotic cell-based biological autocementation kit, was created in this work. Through the surface display of different silica binding peptides on the fungus Yarrowia lipolytica, Euk.cement cells can immobilize onto any particles with a silica containing surface with variable binding intensity. Meanwhile, recombinant MCFP3 released from the cells will slowly consolidate this binding of cells to particles. The metabolism of immobilized living cells will finally complete the carbonate sedimentation and tightly stick the particles together. The system is designed to be initiated by blue light, making it controllable. This autocementation kit can be utilized for industrial and environmental applications that fit our concerns on making the cementation process eco-friendly.

Screening through the PLICable promoter toolbox enhances protein production in Escherichia coli

Escherichia coli is a common host for recombinant protein production in which production titers are highly dependent on the employed expression system. Promoters are thereby a key element to control gene expression levels. In this study, a novel PLICable promoter toolbox was developed which enables in a single cloning step and after a screening experiment to identify out of ten IPTG-inducible promoters (T7, A3, lpp, tac, pac, Sp6, lac, npr, trc and syn) the most suitable one for high level protein production. The target gene is cloned under the control of different promoters in a single and efficient cloning step using the ligase-free cloning method PLICing (phosphorothioate-based ligase-independent gene cloning). The promoter toolbox was firstly validated using three well producible proteins (a cellulase from a metagenome library, a phytase from Yersinia mollaretii and an alcohol dehydrogenase from Pseudomonas putida) and then applied to two enzymes (3D1 DNA polymerase and glutamate dehydrogenase mutant) which are poorly produced in E. coli. By applying our PLICable pET-promoter toolbox, the authors were able to increase production by two-fold for 3D1 DNA polymerase (lac promoter) and 29-fold for glutamate dehydrogenase mutant H52Y (trc promoter).

Recombinant Alpha, Beta, and Epsilon Toxins of Clostridium perfringens: Production Strategies and Applications as Veterinary Vaccines

Clostridium perfringens is a spore-forming, commensal, ubiquitous bacterium that is present in the gastrointestinal tract of healthy humans and animals. This bacterium produces up to 18 toxins. The species is classified into five toxinotypes (A-E) according to the toxins that the bacterium produces: alpha, beta, epsilon, or iota. Each of these toxinotypes is associated with myriad different, frequently fatal, illnesses that affect a range of farm animals and humans. Alpha, beta, and epsilon toxins are the main causes of disease. Vaccinations that generate neutralizing antibodies are the most common prophylactic measures that are currently in use. These vaccines consist of toxoids that are obtained from C. perfringens cultures. Recombinant vaccines offer several advantages over conventional toxoids, especially in terms of the production process. As such, they are steadily gaining ground as a promising vaccination solution. This review discusses the main strategies that are currently used to produce recombinant vaccines containing alpha, beta, and epsilon toxins of C. perfringens, as well as the potential application of these molecules as vaccines for mammalian livestock animals.

COMPARISON OF 16S rRNA-PCR-RFLP, LipL32-PCR AND OmpL1-PCR METHODS IN THE DIAGNOSIS OF LEPTOSPIROSIS

Leptospirosis is still one of the most important health problems in developing countries located in humid tropical and subtropical regions. Human infections are generally caused by exposure to water, soil or food contaminated with the urine of infected wild and domestic animals such as rodents and dogs. The clinical course of leptospirosis is variable and may be difficult to distinguish from many other infectious diseases. The dark-field microscopy (DFM), serology and nucleic acid amplification techniques are used to diagnose leptospirosis, however, a distinctive standard reference method is still lacking. Therefore, in this study, we aimed to determine the presence of Leptospira spp., to differentiate the pathogenic L. interrogans and the non-pathogenic L. biflexa, and also to determine the sensitivity and specificity values of molecular methods as an alternative to conventional ones. A total of 133 serum samples, from 47 humans and 86 cattle were evaluated by two conventional tests: the Microagglutination Test (MAT) and the DFM, as well as three molecular methods, the 16S rRNA-PCR followed by Restriction Fragment Lenght Polymorphism (RFLP) of the amplification products 16S rRNA-PCR-RFLP, LipL32-PCR and OmpL1-PCR. In this study, for L. interrogans, the specificity and sensitivity rates of the 16S rRNA-PCR and the LipL32-PCR were considered similar (100% versus 98.25% and 100% versus 98.68%, respectively). The OmpL1-PCR was able to classify L. interrogans into two intergroups, but this PCR was less sensitive (87.01%) than the other two PCR methods. The 16S rRNA-PCR-RFLP could detect L. biflexa DNA, but LipL32-PCR and OmpL1-PCR could not. The 16S rRNA-PCR-RFLP provided an early and accurate diagnosis and was able to distinguish pathogenic and non-pathogenic Leptospira species, hence it may be used as an alternative method to the conventional gold standard techniques for the rapid disgnosis of leptospirosis.

Effect of Culture Condition Variables on Human Endostatin Gene Expression in Escherichia coli Using Response Surface Methodology

Background

Recombinant human endostatin (rhES) is an angiogenesis inhibitor used as a specific drug for the treatment of non-small-cell lung cancer. As mRNA concentration affects the recombinant protein expression level, any factor affecting mRNA concentration can alter the protein expression level. Response surface methodology (RSM) based on the Box-Behnken design (BBD) is a statistical tool for experimental design and for optimizing biotechnological processes.

Objectives

This investigation aimed to predict and develop the optimal culture conditions for mRNA expression of the synthetic human endostatin (hES) gene in Escherichia coli BL21 (DE3).

Materials and Methods

The hES gene was amplified, cloned, and expressed in the E. coli expression system. Three factors, including isopropyl β-D-1-thiogalactopyranoside (IPTG) concentration, post-induction time, and cell density before induction, were selected as important factors. The mRNA expression level was determined using real-time PCR. The expression levels of hES mRNA under the different growth conditions were analyzed. SDS-PAGE and western blot analyses were carried out for further confirmation of interest-gene expression.

Results

A maximum rhES mRNA level of 376.16% was obtained under the following conditions: 0.6 mM IPTG, 7 hours post-induction time, and 0.9 cell density before induction. The level of rhES mRNA was significantly correlated with post-induction time, IPTG concentration, and cell density before induction (P < 0.05). The expression of the hES gene was confirmed by western blot.

Conclusions

The obtained results indicate that RSM is an effective method for the optimization of culture conditions for hES gene expression in E. coli.

The Optimization of Soluble PTEN Expression in Escherichia coli

As a vital tumor suppressor, PTEN (Phosphatase and tension homolog deleted on chromosome 10) is involved in inherited syndromes, and is among the most frequently inactivated tumor suppressor gene in sporadic cancers. PTEN loss-of-function widely occurs in human cancers via a variety of mechanisms, including genetic alterations and posttranslational modification. These suggest PTEN has a role of functional importance in a variety of cancers. In the present study, we constructed a prokaryotic expression vector that efficiently expresses GST-PTEN (the target protein in which PTEN is fused with glutathione S-transferase tag) in E. coli. We found that the target protein was partially soluble although major portions of the protein remained in the inclusion bodies. Furthermore, we explored the optimal induction temperature, isopropyl β-D-1-thiogalactopyranoside (IPTG) concentration and induction time in a series of experiments. Expression level analysis indicated that PTEN reached its peak level at 36^○C for 8 h with 1.5625mM IPTG, while solubility analysis revealed the optimal induction temperature was at 20^○C, the optimal IPTG concentration was 0.1µM and the optimal induction time was up to 8 h. Taken together, we provide an optimal induction condition for expressing soluble fusion protein of PTEN in E. coli, facilitating further analysis of PTEN’s biological function in vitro.

Expression, purification and characterization of Solanum tuberosum recombinant cytosolic pyruvate kinase

The cDNA encoding for a Solanum tuberosum cytosolic pyruvate kinase 1 (PKc1) highly expressed in tuber tissue was cloned in the bacterial expression vector pProEX HTc. The construct carried a hexahistidine tag in N-terminal position to facilitate purification of the recombinant protein. Production of high levels of soluble recombinant PKc1 in Escherichia coli was only possible when using a co-expression strategy with the chaperones GroES-GroEL. Purification of the protein by Ni(2 +) chelation chromatography yielded a single protein with an apparent molecular mass of 58kDa and a specific activity of 34unitsmg(-1) protein. The recombinant enzyme had an optimum pH between 6 and 7. It was relatively heat stable as it retained 80% of its activity after 2min at 75°C. Hyperbolic saturation kinetics were observed with ADP and UDP whereas sigmoidal saturation was observed during analysis of phosphoenolpyruvate binding. Among possible effectors tested, aspartate and glutamate had no effect on enzyme activity, whereas α-ketoglutarate and citrate were the most potent inhibitors. When tested on phosphoenolpyruvate saturation kinetics, these latter compounds increased S0.5. These findings suggest that S. tuberosum PKc1 is subject to a strong control by respiratory metabolism exerted via citrate and other tricarboxylic acid cycle intermediates.