Ni-NTA Affinity Chromatography Research Articles

Potentiation Effect Of 5FU by Fragaceatoxin C Pore-Forming Toxin in MCF-7 Cell Line

Introduction: Chemotherapy has been restricted due to the high-dose side effects. In the present study, acceleration of the chemotherapeutic drug (5FU) entrance into MCF-7 cells has been explored by using a recombinant form of Fragaceatoxin C (FraC) pore-forming toxin. Methods: In this experimental study, the gene for FraC toxin was order from a commercial source and was sub-cloned into pET28a vector using NcoI and XhoI restriction enzymes. Expression of the protein was induced by IPTG and purification was performed using Ni-NTA affinity chromatography. Hemolysis was tested using a turbidimetric assay. Cytotoxic and potentiation effects of the recombinant toxin on 5FU chemotherapeutic drug were analyzed using trypan blue and MTT assays. T-student test was used to analyze the data using the SPSS v16 software. Significance was defined as P≤0.05 Results: Recombinant FraC toxin was produced in E. coli with 86% purity. Cytotoxic effects of the FraC toxin in MCF-7 cells were dose and time-dependent. the IC50 of FraC toxin on MCF-7 cells was 3.3 mg/ml. Non-toxic concentrations of recombinant FraC toxin enhanced cytotoxic effects of 5FU by a factor of 4 to 6 in different exposure times (24-72 h). Conclusion: Potentiation of the 5FU chemotherapeutic effect by acceleration of its entrance into cancer target cells using FraC pore-forming toxin can reduce its side effects of the chemotherapy.

Expression, purification, characterization and in silico analysis of newly isolated hydrocarbon degrading bleomycin resistance dioxygenase.

In the present investigation, we report cloning, expression, purification and characterization of a novel Bleomycin Resistance Dioxygenase (BRPD). His-tagged fusion protein was purified to homogeneity using Ni-NTA affinity chromatography, yielding 1.2mg of BRPD with specific activity of 6.25 Umg-1 from 600ml of E. coli culture. Purified enzyme was a dimer with molecular weight ~26kDa in SDS-PAGE and ~73kDa in native PAGE analysis. The protein catalyzed breakdown of hydrocarbon substrates, including catechol and hydroquinone, in the presence of metal ions, as characterized via spectrophotometric analysis of the enzymatic reactions. Bleomycin binding was proven using the EMSA gel retardation assay, and the putative bleomycin binding site was further determined by in silico analysis. Molecular dynamic simulations revealed that BRPD attains octahedral configuration in the presence of Fe2+ ion, forming six co-ordinate complexes to degrade hydroquinone-like molecules. In contrary, in the presence of Zn2+ ion BRPD adopts tetrahedral configuration, which enables degradation of catechol-like molecules.

Expression and purification of Murine IFN-γ protein from cloned E. coli strain containing pRSET A Vector with IFN gamma gene

The cloned E. coli cell containing Murine IFN -γ inserted pRSET A vector system was effectively expressed in this study. The induction of the clones was done using IPTG in E.coli and induces mRNA generation and synthesis protein. It has shown an expression of protein with 18 kda in SDS PAGE and western blotting and their size was determined by GENE RUNNER software. This recombinant protein has a 6x His tag and it has been proved as it has shown a potent anti His property in western blotting. The purification of the protein was further done by Ni-NTA affinity chromatography. Nitrilo tri acetic acid (NTA) binds more stably with nickel (Ni) with 4 to 6 ligand binding sites in the coordination sphere of Nickel leaving two sites free to interact with the 6X His tag. The total results conclude that the targeted IFN gamma (408bp mouse gene) cloned in pRSET A was effectively expressed in E. coli BL21 strain cells and purified IFN gamma protein effectively as 1mg/ml. The purified IFN gamma protein may be used to diagnose the antiviral activity and antitumor activity. Key words: IFN gamma, pRSET A, E. coli, SDS PAGE, Western Blotting

PAF-AH and PLA2 activity of Leptospira interrogans LA_2144 gene product

Objective To analyze the enzymatic activity of Leptospira interrogans (L.interrogans) LA_2144 gene product to hydrolyze platelet activating factor acetylhydrolase (PAF-AH) and phosphatidase A2 (PLA2). Methods Bioinformatic softwares were used to predict transmembrane regions, signal peptides and domains of the LA_2144 gene of L. interrogans strain Lai. A prokaryotic expression system for signal peptide-free LA_2144 gene was established. The expressed target recombinant protein rLep2144 was extracted by Ni-NTA affinity chromatography and then renatured. Spectrometry was used to detect the activity of rLep2144 to hydrolyze PAF-AH substrate 2-thio PAF and the Km and Kcat values as well as the activity to hydrolyze PLA2 substrate arachidonoyl 2-thio PC. Real-time fluorescence quantitative RT-PCR and Western blot were performed to detect the transcription, protein expression and secretion of LA_2144 gene during infection of human and mouse vascular endothelial cells (HUVEC and EOMA) with L. interrogans. Results L. interrogans LA_2144 gene contained a signal peptide and a domain belonging to SGNH hydrolase superfamily, but no transmembrane regions. The established prokaryotic expression system for signal peptide-free LA_2144 gene could efficiently express rLep2144. The extracted rLep2144 was shown as a single protein fragment in separation gel and then successfully renatured. rLep2144 had a stronger PAF-AH activity with the Km and Kcat values of 688.235 μmol/L and 0.976/s, but its PLA2 activity was relatively weak. Expression of the LA_2144 gene at mRNA and protein levels in HUVEC and EOMA was rapidly increased after the cells were infected with L. interrogans (P<0.05) and the secretion of LA_2144 gene product could be detected. Conclusions L. interrogans LA_2144 gene product had a stronger PAF-AH and a certain PLA2 activity, which might involve in the hemorrhage and inflammatory response in leptospirosis. Key words: Leptospira interrogans; LA_2144 gene; PAF-AH; PLA2; Enzymatic activity

Design, Expression, Purification and Characterization of the Recombinant Immunotoxin 4D5 scFv-TRAIL

Immunotoxins are chimeric proteins that combine antibodies and toxins in targeted cancer therapy. Despite the promising application prospects, immunogenicity and nonspecific cytotoxicity of immunotoxins with toxins from bacterial or plant origin have hindered their clinical application. In this study, an anti-HER2 single-chain antibody fragment 4D5, was fused to a human-origin antitumor drug, TRAIL to produce a humanized immunotoxin in Escherichia coli BL21 (DE3). An appropriate linker between the domains was selected using the software Antheprot 5.0. The 4D5 scFv-TRAIL was obtained using a SUMO tag for solubility-enhancing and purified by Ni–NTA affinity chromatography after tag removing. The purity and yield of 4D5 scFv-TRAIL reached 92% and 11.6 mg/L in shake flasks, respectively. Additionally, MTT assays showed 4D5 scFv-TRAIL exhibited selective in vitro cytotoxicity on the breast cancer cell line MDA-MB-231 without cytotoxic effect on the normal cell FBHE. Therefore, 4D5 scFv-TRAIL is a potential humanized immunotoxin for treatment of HER2-overexpressing tumor cells.

In-vivo half-life and hypoglycemic bioactivity of a fusion protein of exenatide and elastin-based polypeptide from recombinant Saccharomyces cerevisiae

Exenatide (Ex) is a 39-amino acid peptide of glucagon-like peptide-1 (GLP-1) receptor agonist that was approved by the FDA in 2005 as a Type II diabetes treatment. It shows a 53% homology with GLP-1 but has an extended half-life (ca. 2.4 h) relative to GLP-1 (ca. 2–3 min). In this study, to further extend its in vivo half-life, we constructed a fusion protein (Ex-(EBP)10-6xHis) using a biocompatible and inert elastin-based polypeptide (EBP) as a fusion partner. Valine was inserted into the guest position of the pentapeptide (VPGXG), no linker sequence was inserted in between the EBPs, and (EBP)10-6xHis tag was attached to the C-terminus of exenatide. By using a recombinant Saccharomyces cerevisiae expression system, the fusion protein was expressed and secreted to the broth and purified by Ni-NTA affinity chromatography. Compared with the native exenatide, the physical half-life of the fusion protein was ca. 3.7-fold extended while approximately 72% of the in-vitro insulin secreting activity was maintained. However, the biological half-life measured by a glucose tolerance test (GTT) and the hypoglycemic test in mice was not significantly different from that of the native form. The effects of EBPylation on bioactivity and half-life of the fusion protein are similar to those of PEGylation. The result suggests that the bioactivity and half-life should be carefully balanced to obtain optimal fusion proteins. We expect that EBPylation using an optimal repeat number of EBP can be an alternative to chemical modification for therapeutic biobetters with extended half-life.

Cloning, identification and functional characterization of two cytochrome P450 carotenoids hydroxylases from the diatom Phaeodactylum tricornutum

The diatom microalgal Phaeodactylum tricornutum accumulates a large amount of fucoxanthin. Carotenoids hydroxylases (CHYs) play key roles in fucoxanthin biosynthesis in diatoms. However, not any type of CHYs had been identified in P.tricornutum. In this study, two genes (designated Ptrcyp97b1 and Ptrcyp97b2) were cloned, identified and functionally characterized. They shared high sequence identity (50-94 %) with lutein deficient 1-like proteins from other eukaryotes. The typical catalytic active motifs of cytochrome P450s (CYP) were detected in the amino acid sequences of PtrCYP97B1 and PtrCYP97B2. The two genes were probably due to gene duplication. Ptrcyp97b1 and Ptrcyp97b2 transcriptional expression was up-regulated with distinct patterns under high light conditions. The metabolic profiles of the major carotenoids (β-carotene, zeaxanthin, diadinoxanthin, diatoxanthin and fucoxanthin) were determined based on the high performance liquid chromatography method. The fucoxanthin and diatoxanthin contents were increased, while the β-carotene content was decreased. By truncation of the N-terminal trans-membrane anchor or chloroplast transit peptide and addition of a 6× His-tag, PtrCYP97B1 and PtrCYP97B2 were separately heterologously produced in Escherichia coli and purified by Ni-NTA affinity chromatography. Functional analysis showed that PrtCYP97B2 was able to catalyze the hydroxylation of the β-rings of β-carotene to produce zeaxanthin in β-carotene-accumulating E.coli BL21(DE3) cells. PtrCYP97B1 might have the ability to catalyze the hydroxylation of other substrates other than β-carotene. These results contribute to the further elucidation of xanthophyll biosynthesis in diatoms.

A new microbial gluten-degrading prolyl endopeptidase: Potential application in celiac disease to reduce gluten immunogenic peptides.

Gluten is a complex of proteins present in barley, wheat, rye and several varieties of oats that triggers celiac disease in genetically predisposed subjects. Gluten is notoriously difficult to digest by mammalian proteolytic enzymes and therefore, proline-rich digestion-resistant peptides contain multiple immunogenic epitopes. Prolyl endopeptidases (PEP) hydrolyse internal proline residues on the carboxyl side of peptides and have been proposed for food gluten detoxification and as oral enzyme supplementation for celiacs. The aim of this study was to identify new gluten-degrading microbial enzymes with the potential to reduce gluten immunogenicity by neutralizing its antigenic epitopes. Using a gluten-degrading colony screening approach, a bacterial isolate (2RA3) displaying the highest glutenase activity was selected, characterized and its genome completely sequenced. The identification through 16S rDNA gene sequencing showed a 99,1% similarity to Chryseobacterium taeanense. Hydrolysis of gluten immunogenic peptides (GIP) was further monitored, over a 48-hour period, by colony encapsulation in gliadin-containing microspheres, followed by detection with the G12 anti-GIP monoclonal antibody. Glutenase activity was detected in the extracellular medium of 2RA3 cultures, where gel electrophoresis and gliadin zymography revealed the presence of a ~50 kDa gluten-degrading enzyme. Nano-ESI-Q-TOF of the excised active band identified 7 peptides contained in the protein product predicted for an open reading frame (ORF) in the 2RA3 genome. Based on sequence similarity to the PEP family, the new enzyme was named PEP 2RA3. The PEP 2RA3 coding sequence was PCR-amplified from C. taeanense 2RA3, cloned and expressed in Escherichia coli as a C-terminally His-tagged recombinant protein and purified by Ni-NTA affinity chromatography. The recombinant protein, with predicted molecular mass and isoelectric point of 78.95 kDa and 6.8, respectively, shows PEP activity with standard chromogenic substrates, works optimally at pH 8.0 and 30°C and remains stable at pH 6.0 and 50°C, indicating a potential use in gluten-containing food process applications. The ability of the recombinant enzyme to degrade GIP in beer into smaller peptides was confirmed.

Improved extracellular secretion of β-cyclodextrin glycosyltransferase from Escherichia coli by glycine supplementation without apparent cell lysis

The use of an effective inducer feeding strategy without causing cell lysis presents significant advantage to enhance the secretion of an enzyme to the culture medium of Escherichia coli. The cgt gene encoding β-cyclodextrin glycosyltransferase (β-CGTase) was cloned into pQE30xa as an N-terminal His-tagged protein and transformed into E. coli. The induction strategy was applied towards enhancing the extracellular secretion of the recombinant β-CGTase by increasing permeability of the outer membrane of E. coli. The supplementation of 1.2 mM glycine following 2 h of fermentation at 37°C enhanced the activity of β-CGTase to 38.295 U/mL, which was approximately 1.3-fold higher than the control (without induction). Further flow cytometry analysis was adopted as a rapid and highly reproducible approach to determine the effect of glycine supplementation on the viability of E. coli cells. The supplementation of glycine did not contribute to apparent cell lysis, with no adverse effects on cell viability, hence indicating the effectiveness of glycine in enhancing the extracellular secretion of β-CGTase. The recombinant β-CGTase was then purified through a combination of diafiltration and Ni-NTA affinity chromatography with 18.4-fold increase in purity. An effective glycine feeding strategy could enhance the extracellular secretion of β-CGTase without adverse effects on cell viability. This strategy could be applied potentially to enhance the secretion of a recombinant protein to the culture medium from E. coli cells without having cell lysis.

Expression, Purification and Functional Characterization of Two Recombinant Malate Dehydrogenases from Mortierella isabellina

To study the characteristics of two malate dehydrogenases (MDHs), their coding genes MIMDH1 and MIMDH2 were cloned and expressed in Escherichiacoli BL21 cells. The molecular weights of both recombinant enzymes partially purified using Ni-NTA affinity chromatography were 32 kDa, and the specific activities of purified MIMDH1 and MIMDH2 were 329.3 and 241.3 U/mg protein, respectively. The optimal temperatures for MIMDH1 and MIMDH2 activities were 55 and 30oC, respectively, with 70% MIMDH1 activity and ≥70% MIMDH2 activity remaining after 30 min incubation at 45oC. Addition of 2 mM Zn2+ enhanced MIMDH1 activity, whereas the addition of other metal ions resulted in different degrees of inhibition. The inhibitory effect of Co2+ was most pronounced on MIMDH1, reaching 82.8% inhibition. Addition of 2 mM Ba2+ or Mn2+ increased MIMDH2 activity, the addition of other metal ions resulted in different degrees of inhibition. Furthermore, MIMDH1 was stable at pH range of 7.5–8.5, with optimal activity observed at pH of 8.0. MIMDH2 showed similar stability at the same pH range, but was optimal at pH of 7.5. The Vmax and KM values for recombinant MIMDH1 and MIMDH2 catalyzing the reduction of oxaloacetate to malate were 17.66 µmol mg–1min–1 and 0.541 mM, 15.59 µmol mg–1min–1 and 0.683 mM, respectively.

Cloning, expression and characterization of a HER2-alpha luffin fusion protein in Escherichia coli

In recent decades, immunotoxins have attracted significant attention in treatment of a wide range of diseases including cancers due to their natural origins and their role in blocking crucial pathways within the cells. Ribosome inactivating proteins (RIPs) are efficient molecules in blocking protein synthesis through interactions with ribosomal rRNA molecules. cDNA molecule encoding HER2 scFv antibody fragment originated from trastuzumab attached to the mature alpha luffin gene fragment was subcloned into pET28a expression vector and expressed in different E. coli expression hosts. Identity of the expressed recombinant protein was investigated through western blotting and the fusion protein was purified using Ni-NTA affinity chromatography. The biological activity (toxicity) of the protein was investigated on DNA and RNA samples. A 58 kDa protein was expressed in E. coli. The best protein expression level was achieved in 0.2 mM IPTG at 30 °C in TB medium using E. coli BL21 (DE3) host strain. The fusion protein showed RNase and DNA glycosylase activity on tested RNA and DNA samples. DNA glycosylase activity of the recombinant fusion protein showed that alpha luffin part of this protein is active in conjugation to the scFv molecule and the expressed protein can be further studied in targeted biological in vitro assays.

Recombinant production of a bioactive peptide from spotless smooth-hound (Mustelus griseus) muscle and characterization of its antioxidant activity.

Bioactive peptides are short amino acid sequences with desirable health effects which are derived from animals, plants, and marine sources. In this study, recombinant production of a bioactive peptide (GIISHR) from spotless smooth-hound (Mustelus griseus) muscle and its antioxidant properties is discussed. A gene composed of 12 tandem copies of the peptide sequence was cloned in pET-28a and expressed as a His-tagged polypeptide in Escherichia coli. The recombinant polypeptide was then purified by Ni-NTA affinity chromatography, cleaved by Trypsin and purified by ultrafiltration. DPPH (1,1-diphenyl-2-picrylhydrazyl), ABTS (2,2'-azinobis-3-ethylbenzotiazoline-6-sulfonic acid) and hydroxyl radical scavenging activity assays, ferric reducing antioxidant power (FRAP) assay and β-carotene bleaching test were used to characterize the antioxidant activity of the GIISHR. Liquid chromatography-mass spectrometry analysis revealed 60% purity for released bioactive peptide. Production yield was estimated as 60-80mg GIISHR active peptide per 1L bacterial culture. Antioxidant activity assays indicated that the antioxidant activity was increased with increase in peptide concentration. Though the DPPH radical scavenging activity, FRAP and β-carotene bleaching power of the peptide were lower than those of the synthetic antioxidant tert-butylhydroquinone (TBHQ), the ABTS and hydroxyl radical scavenging activities of the peptide (at a concentration of 20mg/mL) were similar to those of TBHQ (at a concentration of 0.1mg/mL). The findings of the present study may be helpful in development of a process for production of the bioactive antioxidant peptides and its application in food industry.

Purification and biochemical characterization of FrsA protein from Vibrio vulnificus as an esterase.

Fermentation-respiration switch protein (FrsA) was thought to play an important role in controlling the metabolic flux between respiration and fermentation pathways, whereas the biochemical function of FrsA was unclear yet. A gene coding for FrsA protein from Vibrio vulnificus was chemically synthesized. The recombinant VvFrsA was expressed as a soluble protein and purified by Ni-NTA affinity chromatography. The protein had a subunit molecular weight of ca. 45 kDa by SDS-PAGE and preferred short-chain esters when p-nitrophenyl alkanoate esters were used as substrates. Optimum condition for VvFrsA was found to be at pH 9.0 and 50 °C. The protein retained high esterase activity at alkaline condition and would denature slowly at over 50 °C. With p-nitrophenyl acetate as the substrate, the Km and kcat were determined to be 18.6 mM and 0.67 s-1, respectively, by steady-state kinetic assay. Molecular dynamics simulation and docking model structure revealed that p-nitrophenyl acetate could be the substrate of VvFrsA. In conclusion our results demonstrated that the protein was able to catalyze the hydrolysis of esters, especially p-nitrophenyl acetate, for the first time.

Bacteria-Derived Recombinant Human ANGPTL8/Betatrophin Significantly Increases the Level of Triglyceride

ANGPTL8/Betatrophin has been implicated in the regulation of both glucose and triglyceride metabolism. However, its role in regulating glucose metabolism by promoting β cell proliferation remains controversial, and its physiological functions and molecular targets are largely unknown. Hence, it is of great importance to make recombinant protein and test its effects on β cell mass directly. In this study, the mature form gene of human ANGPTL8/betatrophin was obtained through chemical synthesis on to the vector pUCE, and the fusion protein was expressed in the Transetta (DE3)/pEASY-E2-betatrophin strain. The inclusion bodies were solubilized in urea and purified by Ni–NTA affinity chromatography. The yield of purified ANGPTL8/betatrophin was approximately 20 mg per liter of culture medium. In vitro studies revealed that the recombinant ANGPTL8/betatrophin had no proliferation effect on MIN6 cells but promoted TG levels in HepG2 cells. This method to generate bioactive ANGPTL8/betatrophin is a simple, practical and user-friendly protocol.

Cloning, expression and characterization of β- and γ‑carbonic anhydrase from Bacillus sp. SS105 for biomimetic sequestration of CO2.

Bacterium Bacillus sp. SS105, isolated from Free Air CO2 Enriched (FACE) soil was previously screened for carbonic anhydrase activity and CO2 sequestration. In this study, strain was selected to amplify carbonic anhydrase encoding genes. The CA genes from Bacillus sp. SS105 were found to be homologous with beta‑carbonic anhydrase (β-CA) and gamma‑carbonic anhydrase (γ-CA). Both types of CA genes was cloned in pET30b (+) and expressed in E coliBL21 (DE3) with His-tag at the N-terminus. The recombinant proteins were purified by Ni-NTA affinity chromatography. The molecular size of β-CA and γ-CA were approximately 27 kDa and 25 kDa respectively. The optimum pH and temperature were found to be 8.0 and 37 °C respectively. The Zn+ was enhancing the CAs enzyme activity. Anions and modulators showed inhibitory effect on CAs at specific concentration. Functional domain analysis of both CA proteins showed conserved region of respective proteins. Recombinant enzymes were used for bio-mineralization based conversion of atmospheric CO2 into valuable calcite. Calcite formation was evaluated with or without use of enzymes and confirmed by SEM and XRD analysis. SEM result confirmed the conversion of flower-shaped unstable form of vaterite to hexagonal cubic stable form of calcite in presence of enzymes.

Expression of a Pseudomonas aeruginosa-targeted antimicrobial peptide T9W in Bacillus subtilis using a maltose-inducible vector

Abstract The T9W is a variant of pig myeloid antimicrobial peptide-36 (PMAP 36) that displays efficient and specific activity against Pseudomonas aeruginosa. It may represent a promising agent for anti-pseudomonas therapies, so a large quantity of T9W is needed for pharmacological study and clinical use. Recombinant T9W was successfully produced by Bacillus subtilis WB800 N using the maltose-inducible promoter Pglv. After 36 h of induction by 5% maltose, 6×His-SUMO-T9W was directly secreted into culture medium. Then, 6×His-SUMO-T9W was purified by Ni-NTA affinity chromatography, and then 32 mg/L of fusion peptide was obtained. Then, the purified 6×His-SUMO-T9W was digested by SUMO protease, thus releasing the recombinant T9W. Recombinant T9W showed high antimicrobial activity against Pseudomonas aeruginosa and extremely weak activity against other gram-negative (Escherichia coli, Salmonella typhimurium) and gram-positive bacteria (Staphylococcus epidermidis, Staphylococcus aureus). When the concentration of recombinant T9W reached the maximum (256 μM), no hemolytic activity was observed. Recombinant T9W has similar activity to synthetic T9W. These results suggested that this method provided an economical and environmentally friendly approach to producing anti-pseudomonas agent T9W in Bacillus subtilis.

Development of a Lateral Flow Immunoassay using recombinant GRA7 antigen to detect Toxoplasma gondii IgG antibodies

Toxoplasma gondii is an intracellular protozoan parasite that causes toxoplasmosis and is of medical importance in pregnant women and immunosuppressed patients. In recent years, many methods have been developed for the detection of infection caused by this parasite; however, most of the developed methods are not adequately sensitive. The dense granular antigen (GRA) 7 is a highly immunogenic protein that is used as a specific antigen for the diagnosis of toxoplasmosis. This study was designed to produce recombinant GRA7 (rGRA7) antigen in bacterial system in order to be applied as an antigen for developing a simple and rapid lateral flow immunoassay test strip using a gold nanoparticle-pAb conjugate probe to detect Toxoplasma IgG-specific antibodies in human sera. After the extraction of genomic DNA from RH strain tachyzoites, polymerase chain reaction (PCR) was performed using specific primers considering restriction sites and BglII and XhoI enzymes. Subsequently, the GRA7 gene was cloned in pET-32a (+) expression vector, and then pET-32a(+)-GRA7 was transformed into E. coli Rosetta (DE3). The induction of protein production was accomplished by IPTG, and the product was finally purified by Ni-NTA affinity chromatography. In order to make the strip test, the anti-human gold nanoparticle conjugate was applied on conjugate pad, rGRA7 antigen was immobilized to a nitrocellulose membrane as the capture agent, and sample and absorbance pads were assembled on a backing card. For the analysis of the sensitivity and specificity of the assay, the selected patients’ sera samples were tested by standard chemiluminescence immunoassay (CLIA) method, and then compared with TOXO-IgG strip results. The findings showed that the use of rGRA7 is an accurate, sensitive, and inexpensive technique for the rapid detection of anti-Toxo­plasma IgG in human sera. Therefore, rGRA7 can be applied as a diagnostic agent in laboratories.

Recombinant expression and purification of a functional bacterial metallo-chaperone PbrD-fusion construct as a potential biosorbent for Pb(II)

PbrD is a lead (II) binding protein encoded by the pbr lead resistance operon found exclusively in Cupriavidus metallidurans CH34. Its ability to sequester Pb(II) shows potential for it to be developed as a biosorbent for Pb in the bioremediation of contaminated wastewaters. In this study the pbrD gene from C. metallidurans CH34 was transformed and overexpressed in Escherichia coli BL21 (DE3) using the pET32 Xa/Lic vector. Optimal expression of recombinant (r)PbrD (∼50 kDa) was achieved post-induction with IPTG within inclusion bodies (IBs). Inclusion bodies were solubilised by denaturation and purified by Ni-NTA affinity chromatography. The purified denatured protein containing the N-terminal Trx•Tag™, His•Tag® and S®Tag™ was refolded in vitro via dialysis to a biologically functional form. Circular dichroism spectra of refolded rPbrD-fusion protein indicated a high degree of turns, β-sheets and 310 helices content and tryptophan fluorescence showed a structural conformational change in the presence of Pb(II). Refolded rPbrD-fusion protein bound 99.7% of Pb(II) when mixed with lead nitrate in ten-fold increasing concentrations. Adsorption isotherms including Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models were applied to determine the biosorption mechanism. A biologically functional rPbrD-fusion protein has potential application in the development of a biosorbent for remediation of Pb(II) from wastewater.

Construction of a synthetic protein using PCR with a high essential amino acid content for nutritional purposes.

Ovalbumin is considered a protein of high nutritional value because it contains essential amino acids and is highly digestible. Therefore, it has a high biological value. Currently, the high food demand requires worldwide attention because food production is insufficient. Therefore, other alternatives are necessary to satisfy food demands, such as protein engineering. In this work, a protein with a high essential amino acid content similar to ovalbumin was synthesized by protein engineering, expressed, and digested in vitro. The assembly and sequential overlap extension PCR strategy was used to synthesize a 345-bp gene that encodes a high essential amino acid content protein (HEAAP). The 345-bp product was cloned into the vector pBAD TOPO®, and expressed in Escherichia coli BL21. PCR reactions and sequencing demonstrated the presence, orientation, and correct sequence of the insert. HEAAP expression was induced by L-arabinose and then purified using Ni-NTA affinity chromatography. The expression in E. coli was low and barely detected by Western blot assay. The in vitro multienzyme digestibility of HEAAP was around 79%, which suggests that the protein is potentially nutritious. Virtual analysis classifies the protein as unstable and hydrophilic, with a half-life in E. coli of 10h. The recombinant HEAAP was successfully synthesized, but it is necessary to improve the digestibility and to optimize expression including selecting other expression models.

High expression and immunogenicity analysis of HA globular head domain of H5 subtype avian influenza virus produced in Pichia pastoris

To evaluate the immunogenicity of HA globular head domain of H5 subtype influenza virus (H5HA), the gene of H5HA was optimized and the recombinant pPICZaA-H5HA expressing vector was constructed and transfected into Pichia pastoris. The expression of the recombinant H5HA was confirmed by SDS-PAGE and Western blotting and the results demonstrated that the recombinant H5HA (37 kDa) was highly expressed in Pichia pastoris with concentration of 0.2 mg/mL in medium. The recombinant H5HA was concentrated and purified using Ni-NTA affinity chromatography. The immunogenicity of H5HA was evaluated by immunizing eight groups of chicken through intranasal or intramuscular injection with different doses of purified H5HA combined with different adjuvants, respectively. The results showed that the recombinant H5HA could induce high level IgG (HI titer was 1:64 and neutralizing antibody titer was 1:218) and the optimal dosage of the recombinant H5HA was 50 μg combined with oil. In addition, intramuscular injection was better than nasal immunization. This study provided a theoretical support for subunit vaccine development.