This paper describes the recombinant production of a biologically active Epstein-Barr virus BZLF1 trans-activator, i.e., Z-encoded broadly reactive activator (ZEBRA), that recognized specific DNA motifs. We used auto-induction for histidine-tagged BZLF1 expression in Escherichia coli and immobilized cobalt affinity membrane chromatography for protein purification under native conditions. We obtained the purified BZLF1 at a yield of 5.4mg per gram of wet weight cells at 75% purity, in which 27% of the recombinant BZLF1 remained biologically active. The recombinant BZLF1 bound to oligonucleotides containing ZEBRA response elements, either AP-1 or ZIIIB, but not a ZIIIB mutant. The recombinant BZLF1 showed a specific DNA-binding activity which could be useful for functional studies.
Recombinant protein production is a significant biotechnological process as it allows researchers to produce a specific protein in desired quantities. Escherichia coli (E. coli) is the most popular heterologous expression host for the production of recombinant proteins due to its advantages such as low cost, high-productivity, well-characterized genetics, simple growth requirements and rapid growth. There are a number of factors that influence the expression level of a recombinant protein in E. coli which are the gene to be expressed, the expression vector, the expression host, and the culture condition. The major motivation to develop our database, EcoliOverExpressionDB, is to provide a means for researchers to quickly locate key factors in the overexpression of certain proteins. Such information would be a useful guide for the overexpression of similar proteins in E. coli. To the best of the present researchers' knowledge, in general and specifically in E. coli, EcoliOverExpressionDB is the first database of recombinant protein expression experiments which gathers the influential parameters on protein overexpression and the results in one place.
Squalene synthase (SS) is the key precursor and first committed enzyme of the sterol biosynthesis pathway. In a previous work, SS has been identified as one of the immunogenic proteins that could be a potential diagnostic candidate for the pathogenic fungus Candida tropicalis. In this study, SS from C. tropicalis was cloned and expressed as recombinant protein in Pichia pastoris to investigate its reactivity with serum antibodies. ERG9 gene that encodes for SS was amplified by PCR and cloned in-frame into pPICZB expression vector. The recombinant construct was then transformed into P. pastoris GS115 host strain. Expression of the recombinant protein was confirmed by SDS-PAGE and Western blot analysis using anti-His tag probe. Optimal protein production was achieved by cultivating the culture with 1.0% methanol for 72h. The recombinant protein was purified to approximately 97% pure in a single step immobilized metal affinity chromatography with a yield of 70.3%. Besides, the purified protein exhibited specific reactivity with immune sera on Western blot. This is the first report on heterologous expression of antigenic SS from C. tropicalis in P. pastoris which can be exploited for large-scale production and further research. The results also suggested that the protein might be of great value as antigen candidate for serodiagnosis of Candida infection.
Thermostable lipases are important biocatalysts, showing many interesting properties with industrial applications. Previously, a thermophilic Bacillus sp. strain L2 that produces a thermostable lipase was isolated. In this study, the gene encoding for mature thermostable L2 lipase was cloned into a Pichia pastoris expression vector. Under the control of the methanol-inducible alcohol oxidase (AOX) promoter, the recombinant L2 lipase was secreted into the culture medium driven by the Saccharomyces cerevisiae alpha-factor signal sequence. After optimization the maximum recombinant lipase activity achieved in shake flasks was 125 U/ml. The recombinant 44.5 kDa L2 lipase was purified 1.8-fold using affinity chromatography with 63.2% yield and a specific activity of 458.1 U/mg. Its activity was maximal at 70 degrees C and pH 8.0. Lipase activity increased 5-fold in the presence of Ca2+. L2 lipase showed a preference for medium to long chain triacylglycerols (C(10)-C(16)), corn oil, olive oil, soybean oil, and palm oil. Stabilization at high temperature and alkaline pH as well as its broad substrate specificity offer great potential for application in various industries that require high temperature operations.
An organic solvent tolerant (OST) lipase gene from Bacillus sphaericus 205y was successfully expressed extracellularly. The expressed lipase was purified using two steps purification; ultrafiltration and hydrophobic interaction chromatography (HIC) to 8-fold purity and 32% recovery. The purified 205y lipase revealed homogeneity on denaturing gel electrophoresis and the molecular mass was at approximately 30 kDa. The optimum pH for the purified 205y lipase was 7.0-8.0 and its stability showed a broad range of pH value between pH 5.0 to 13.0 at 37 degrees C. The purified 205y lipase exhibited an optimum temperature of 55 degrees C. The activity of the purified lipase was stimulated in the presence of Ca2+ and Mg2+. Ethylenediaminetetraacetic acid (EDTA) has no effect on its activity; however inhibition was observed with phenylmethane sulfonoyl fluoride (PMSF) a serine hydrolase inhibitor. Organic solvents such as dimethylsulfoxide (DMSO), methanol, p-xylene and n-decane enhanced the activity. Studies on the effect of oil showed that the lipase was most active in the presence of tricaprin (C10). The lipase exhibited 1,3 positional specificity.
Tuberculosis remains a major infectious disease with over 8 million new cases and 2 million deaths annually. Therefore, a vaccine more potent than BCG is desperately needed. In this regard, an approximately 800 bp DNA encoding a mycobacterial synthetic gene designated as VacIII (containing ubiquitin gene UbGR and four immunogenic mycobacterial epitopes or genes of ESAT-6, Phos1, Hsp 16.3, and Mtb8.4) was sub-cloned into a bacterial expression vector of pRSET-B resulting in a 6 x His-VacIII fusion gene construction. This recombinant clone was over expressed in Escherichia coli BL-21 (DE-3). The expressed fusion protein was found almost entirely in the insoluble form (inclusion bodies) in cell lysate. The inclusion bodies were solubilized with 8M urea and the recombinant protein was purified by Ni-NTA column and dialyzed by urea gradient dialysis. This method produced a relatively high yield of recombinant VacIII protein and the cloned VacIII gene offers the potential development of other vaccine formats such as DNA vaccine and recombinant vaccine.
In the present work, a single-step purification of recombinant nucleocapsid protein (NP) of the Newcastle disease virus (NDV) directly from unclarified feedstock using an expanded bed adsorption chromatography (EBAC) was developed. Streamline 25 column (ID = 25 mm) was used as a contactor and Streamline chelating adsorbent immobilized with Ni2+ ion was used as affinity adsorbent. The dynamic binding capacity of Ni2+ -loaded Streamline chelating adsorbent for the NP protein in unclarified feedstock was found to be 2.94 mg ml(-1) adsorbent at a superficial velocity of 200 cm h(-1). The direct purification of NP protein from unclarified feedstock using expanded bed adsorption has resulted in a 31% adsorption and 9.6% recovery of NP protein. The purity of the NP protein recovered was about 70% and the volume of processing fluid was reduced by a factor of 10. The results of the present study show that the IMA-EBAC developed could be used to combine the clarification, concentration and initial purification steps into a single-step operation.
The extracellular production of T1 lipase was performed by co-expression of pJL3 vector encoding bacteriocin release protein in prokaryotic system. Secretory expression was optimized by considering several parameters, including host strains, inducer (IPTG) concentration, media, induction at A(600 nm), temperature, and time of induction. Among the host strains tested, Origami B excreted out 18,100 U/ml of lipase activity into culture medium when induced with 50 microM IPTG for 12 h. The Origami B harboring recombinant plasmid pGEX/T1S and pJL3 vector was chosen for further study. IPTG at 0.05 mM, YT medium, induction at A(600 nm) of 1.25, 30 degrees C, and 32 h of induction time were best condition for T1 lipase secretion with Origami B as a host.
Bacteriocin release proteins (BRPs) can be used for the release of heterologous proteins from the Escherichia coli cytoplasm into the culture medium. The gene for a highly thermostable alkaline protease was cloned from Bacillus stearothermophilus F1 by the polymerase chain reaction. The recombinant F1 protease was efficiently excreted into the culture medium using E. coli XL1-Blue harboring two vectors: pTrcHis bearing the protease gene and pJL3 containing the BRPs. Both vectors contain the E. coli lac promoter-operator system. In the presence of 40 microM IPTG, the recombinant F1 protease and the BRP were expressed and mature F1 protease was released into the culture medium. This opens the way for the large-scale production of this protease in E. coli. The recombinant enzyme was purified through a one-step heat treatment at 70 degrees C for 3h and this method purified the protease to near homogeneity. The purified enzyme showed a pH optimum of 9.0, temperature optimum of 80 degrees C, and was stable at 70 degrees C for 24h in the pH range from 8.0 to 10.0. The enzyme exhibited a high degree of thermostability with a half-life of 4 h at 85 degrees C, 25 min at 90 degrees C, and was inhibited by the serine protease inhibitor phenylmethylsulfonyl fluoride (PMSF).
Xylanases (EC 3.2.1.8) are essential enzymes due to their applications in various industries such as textile, animal feed, paper and pulp, and biofuel industries. Halo-thermophilic Rhodothermaceae bacterium RA was previously isolated from a hot spring in Malaysia. Genomic analysis revealed that this bacterium is likely to be a new genus of the family Rhodothermaceae. In this study, a xylanase gene (1140 bp) that encoded 379 amino acids from the bacterium was cloned and expressed in Escherichia coli BL21(DE3). Based on InterProScan, this enzyme XynRA1 contained a GH10 domain and a signal peptide sequence. XynRA1 shared low similarity with the currently known xylanases (the closest is 57.2-65.4% to Gemmatimonadetes spp.). The purified XynRA1 achieved maximum activity at pH 8 and 60 °C. The protein molecular weight was 43.1 kDa XynRA1 exhibited an activity half-life (t1/2) of 1 h at 60 °C and remained stable at 50 °C throughout the experiment. However, it was NaCl intolerant, and various types of salt reduced the activity. This enzyme effectively hydrolyzed xylan (beechwood, oat spelt, and Palmaria palmata) and xylodextrin (xylotriose, xylotetraose, xylopentaose, and xylohexaose) to produce predominantly xylobiose. This xylanase is the first functionally characterized enzyme from the bacterium, and this work broadens the knowledge of GH10 xylanases.
The Aspergillus flavus NSH9 gene, encoding a pH and thermostable glucoamylase with a starch binding domain (SBD), was expressed in Pichia pastoris to produce recombinant glucoamylase (rGA2). The full-length glucoamylase gene (2039 bp), and cDNA (1839 bp) encode a 612 amino acid protein most similar to glucoamylase from Aspergillus oryzae RIB40; the first 19 amino acids are presumed to be a signal peptide for secretion, and the SBD is at the C-terminal. The cDNA was successfully secreted by Pichia at 8.23 U mL-1, and the rGA2 was found to be: a 80 kDa monomer, stable from pH 3.0-9.0, with optimum catalytic activity at pH 5.0, active at temperatures up to 80°C (rGA2 retained 58% of its activity after 60 min of incubation at 70°C), and metal ions such as Na+, K+, Ca++ and Mg++ enhanced rGA2 enzyme activity. The starch degrading ability of rGA2 was also observed on raw sago starch and where prolonged incubation generated larger, deeper, holes on the starch granules, indicating rGA2 is an excellent candidate for industrial starch processing applications.
Neonatal Fc-receptor (FcRn) with its affinity to immunoglobulin G (IgG) has been the subject of many pharmacokinetic studies in the past century. This protein is well known for its unique feature in maintaining the circulating IgG from degradation in blood plasma. FcRn is formed by non-covalent association between the α-chain with the β-2-microglobulin (β2m). Many studies have been conducted to produce FcRn in the laboratory, mainly using mammalian tissue culture as host for recombinant protein expression. In this study, we demonstrate a novel strategy to express the α-chain of FcRn using Escherichia coli as the expression host. The expression vector that carries the cDNA of the α-chain was transformed into expression host, Rosetta-gami 2 strain for inducible expression. The bacterial culture was grown in a modified growth medium which constitutes of terrific broth, sodium chloride (NaCl), glucose and betaine. A brief heat shock at 45 °C was carried out after induction, before the temperature for expression was reduced to 22 °C and grown for 16 h. The soluble form of the α-chain of FcRn expressed was tested in the ELISA and dot blot immunoassay to confirm its native functionality. The results implied that the α-chain of FcRn expressed using this method is functional and retains its pH-dependent affinity to IgG. Our study significantly suggests that the activity of human FcRn remain active and functional in the absence of β2m.
SAG1-related sequence 3 (SRS3) is one of the major Toxoplasma gondii tachyzoite surface antigens and has been shown to be potentially useful for the detection of toxoplasmosis. This protein is highly conformational due to the presence of six disulfide bonds. To achieve solubility and antigenicity, SRS3 depends on proper disulfide bond formation. The aim of this study was to over-express the SRS3 protein with correct folding for use in serodiagnosis of the disease. To achieve this, a truncated SRS3 fusion protein (rtSRS3) was produced, containing six histidyl residues at both terminals and purified by immobilized metal affinity chromatography. The refolding process was performed through three methods, namely dialysis in the presence of chemical additives along with reduced/oxidized glutathione and drop-wise dilution methods with reduced/oxidized glutathione or reduced DTT/oxidized glutathione. Ellman's assay and ELISA showed that the protein folding obtained by the dialysis method was the most favorable, probably due to the correct folding. Subsequently, serum samples from individuals with chronic infection (n = 76), probable acute infection (n = 14), and healthy controls (n = 81) were used to determine the usefulness of the refolded rtSRS3 for Toxoplasma serodiagnosis. The results of the developed IgG-ELISA showed a diagnostic specificity of 91% and a sensitivity of 82.89% and 100% for chronic and acute serum samples, respectively. In conclusion, correctly folded rtSRS3 has the potential to be used as a soluble antigen for the detection of human toxoplasmosis.
Cellobiohydrolases catalyze the processive hydrolysis of cellulose into cellobiose. Here, a Trichoderma virens cDNA predicted to encode for cellobiohydrolase (cbhI) was cloned and expressed heterologously in Aspergillus niger. The cbhI gene has an open reading frame of 1518 bp, encoding for a putative protein of 505 amino acid residues with a calculated molecular mass of approximately 54 kDa. The predicted CbhI amino acid sequence has a fungal type carbohydrate binding module separated from a catalytic domain by a threonine rich linker region and showed high sequence homology with glycoside hydrolase family 7 proteins. The partially purified enzyme has an optimum pH of 4.0 with stability ranging from pH 3.0 to 6.0 and an optimum temperature of 60 °C. The partially purified CbhI has a specific activity of 4.195 Umg-1 and a low Km value of 1.88 mM when p-nitrophenyl-β-D-cellobioside (pNPC) is used as the substrate. The catalytic efficiency (kcat/Km) was 5.68 × 10-4 mM-1s-1, which is comparable to the CbhI enzymes from Trichoderma viridae and Phanaerochaete chrysosporium. CbhI also showed activity towards complex substrates such as Avicel (0.011 Umg-1), which could be useful in complex biomass degradation. Interestingly, CbhI also exhibited a relatively high inhibition constant (Ki) for cellobiose with a value of 8.65 mM, making this enzyme more resistant to end-product inhibition compared to other fungal cellobiohydrolases.
Depolymerase is an enzyme that plays an important role in the hydrolysis of polyhydroxyalkanoates [PHAs]. In the current study, Burkholderia cepacia DP1 was obtained from Penang, Malaysia in which the enzyme was purified using ion exchange and gel filtration (Superdex-75) column chromatography. The molecular mass of the enzyme was estimated to be 53.3 kDa using SDS-PAGE. The enzyme activity was increased to 36.8 folds with the recovery of 16.3% after purification. The enzyme activity was detected between pH 6.0-10 and at 35-55 °C with pH 6.0 and 45 °C facilitating the maximum activity. Depolymerase was inactivated by Tween-20, Tween-80, SDS and PMSF, but insensitive to metal ions (Mg2+, Ca2+, K+, Na2+, Fe3+) and organic solvents (methanol, ethanol, and acetone). The apparent Km values of the purified P(3HB) depolymerase enzyme for P(3HB) and P(3HB-co-14%3HV) were 0.7 mg/ml and 0.8 mg/ml, respectively. The Vmax values of the purified enzyme were 10 mg/min and 8.89 mg/min for P(3HB) and P(3HB-co-14%3HV), respectively. The current study discovered a new extracellular poly(3-hydroxybutyrate) [P(3HB)] depolymerase enzyme from Burkholderia cepacia DP1 isolated and purified to homogeneity from the culture supernatant. To the best of our knowledge, this is the first report demonstrating the purification and biochemical characterization of P(3HB) depolymerase enzyme from genus Burkholderia.
This study described the isolation of the coding region of human topoisomerase I (TopoI) from MDA-MB-231 and the expression of multiple copy recombinant genes in four Pichia pastoris strains. First, polymerase chain reaction (PCR)-amplification of the enzyme coding region was performed. The PCR fragment was cloned into pPICZ-α-A vector and sequenced. It was then transformed into X33, GS115, SMD1168H and KM71H strains of Pichia. PCR-screening for positive clones was performed, and estimation of multiple copy integrants in each Pichia strain was carried out using agar plates containing increasing concentrations of Zeocin(®). The selected clones of multiple copy recombinant genes were then induced for TopoI expression in shaker flasks. GS115 and SMD1168 were found to be better Pichia strains to accommodate the recombinant gene for the expression of TopoI extracellularly. However, the DNA relaxation activity revealed that only the target enzyme in the culture supernatants of GS115-pPICZ-α-A-TopoI exhibited consistent enzyme activity over the cultivation time-points. Active enzyme activity was inhibited by Camptothecin. The enzyme produced can be used for in-house gel-based DNA relaxation assay development in performing high throughput screening for target-specific growth inhibitors that display similar effect as the TopoI inhibitors. These inhibitors may contribute to the improvement of the treatment of cancer patients.