Control Of T7 Promoter Research Articles

Production and applications of fluorobody from redox-engineered Escherichia coli

Efficient selection and production of antibody fragments in microbial systems remain to be a challenging process. To optimize microbial production of single-chain variable fragments (scFvs), we have chosen five model targets, 1) a hapten, Zearalenone (ZEN) mycotoxin, along with infectious agents 2) rabies virus, 3) Propionibacterium acnes, 4) Pseudomonas aeruginosa, and a cancer cell 5) acute myeloid leukemia cell line (HL-60). The scFv binders were affinity selected from a non-immunized human phage display scFv antibody library and genetically fused to the N-terminus of emerald green fluorescent protein (EmGFP). The scFv-EmGFP fusion constructs were subcloned into an expression vector, under the control of T7 promoter, C-terminally tagged with hexa-histidine and expressed in different Escherichia coli (E. coli) hosts. This enabled the detection of cells that expressed the correct scFv-EmGFP fusion, termed fluorobody, via bright fluorescent signal in the cytoplasm. Among the three E. coli hosts tested, an engineered E. coli B strain called SHuffle B that promotes disulfide bond formation in the cytoplasm appeared to be the most appropriate host. The recombinant fluorobodies were well expressed (2–8 mg/L), possessed the fluorescence property of EmGFP, and retained the ability to bind to their cognate targets. Their specific bindings were demonstrated by ELISA, fluorescence-linked immunosorbent assay (FLISA), flow cytometry, and fluorescent microscope imaging. The fluorobody expression platform in this study could be further adopted as a one-step immunostaining technique based on scFv, isolated from phage display library to numerous desired targets.Key points• E. coli SHuffle express T7 is a suitable expression host for scFv-EmGFP (fluorobody)• Only the clones harboring scFv-EmGFP plasmid will show bright fluorescent signal• This platform can be used to produce fluorobodies for numerous purposesGraphical abstract

Unpredictive Expression of recombinant proteins under the control of different promoters in different expression systems

Synthetic human proinsulin gene with E.coli preferred codon and extra methionine was expressed as 30% of total cellular protein. Fusing seven aminoacids of well expressed protein to the N’-terminus did not alter the expression of recombinant proinsulin. Doubling the copies of proinsulin gene will not doubles the expression. The protein was expressed as inclusion bodies. Changing the distances between ribosome binding site and start codon effect the expression in an unexplained way. Ten nucleotide distance gave expression of 2-4% and with 12 nucleotides, expression decreasaes up to 1-2%.. Incorporating 10 different nucleotides at the start of proinsulin gene decreases the mRNA secondary structure but did not alter the expression. Metabolic instability, rapid degradation of mRNA or accumulation of protein may down regulate expression of mRNA. High expression of azurin gene in pET22b vector was obtained when fused with 19 aminoacid signal peptide in BL21-Codon Plus (DE3) cells. PE38KDEL can be expressed in huge quantities in Escherichia coli by using the recombinant vector PE38KDEL/pET under control of T7 promoter and E. coli host strain BL21 (DE3) CodonPlus. The protein expressed as soluble and insoluble inclusion bodies the expression in soluble form was more pronounced. When human interferone alpha2|B gene and E.coli amino peptidase genes were expressed bicistronically in expression plasmid pET-21a (+). There was negligible expression of human interferone alpha 2B. PelB fused DNA polymerase I was expressed as soluble fraction with maximum expression with 0.5mM IPTG and 20mM lactose. Recombinant protein expression in expression host can be improved by mRNA stability, codon bias, and controlling inclusion bodies formation and changing genetic tools in different combinations. There are other controlling factors of protein expression i.e., metabolic instability, rapid degradation of mRNA or accumulation of protein may downregulate expression of mRNA.

Effective production of human growth factors in Escherichia coli by fusing with small protein 6HFh8

BackgroundGrowth factors (GFs) are signaling proteins that affect cellular processes such as growth, proliferation, and differentiation. GFs are used as cosmeceuticals, exerting anti-wrinkle, anti-aging, and whitening effects, and also as pharmaceuticals to treat wounds, growth failure, and oral mucositis. However, in mammalian and bacterial cells, low productivity and expression in inclusion bodies, respectively, of GFs does not satisfy the consumer demand. Here, we aimed to develop a bacterial expression system that produces high yields of soluble GFs that can be purified in their native forms.ResultsWe present Fh8, an 8-kDa peptide from Fasciola hepatica with an N-terminal hexa-histidine (6HFh8), as a fusion partner for enhanced human GF production in recombinant Escherichia coli. The fusion partner harboring a tobacco etch virus (TEV) protease cleavage site was fused to the N-terminus of 10 human GFs: acidic and basic fibroblast growth factors (aFGF and bFGF, respectively), epidermal growth factor (EGF), human growth hormone (hGH), insulin-like growth factor 1 (IGF-1), vascular endothelial growth factor 165 (VEGF165), keratinocyte growth factor 1 (KGF-1), placental growth factor (PGF), stem cell factor (SCF), and tissue inhibitor of metalloproteinase 1 (TIMP-1). The fusion proteins were expressed in E. coli under the control of T7 promoter at three temperatures (25 °C, 30 °C, and 37 °C). All individual fusion proteins, except for SCF and TIMP-1, were successfully overexpressed in cytoplasmic soluble form at more than one temperature. Further, the original aFGF, IGF-1, EGF, and VEGF165 proteins were cleaved from the fusion partner by TEV protease. Five-liter fed-batch fermentation approaches for the 6HFh8-aFGF (lacking disulfide bonds) and 6HFh8-VEGF165 (a cysteine-rich protein) were devised to obtain the target protein at concentrations of 9.7 g/l and 3.4 g/l, respectively. The two GFs were successfully highly purified (> 99% purity). Furthermore, they exerted similar cell proliferative effects as those of their commercial equivalents.ConclusionsWe demonstrated that 6HFh8-GF fusion proteins could be overexpressed on a g/l scale in the cytoplasm of E. coli, with the GFs subsequently highly purified and maintaining their biological activity. Hence, the small protein 6HFh8 can be used for efficient mass-production of various GFs.

Biotechnological approach for the production of L-asparaginase from locally Bacillus subtilis isolate

Background and objectives L-asparaginase is a therapeutic enzyme used for the treatment of hematopoietic diseases, for example, acute lymphoblastic leukemia. It has many applications other than as an anticancer agent, which includes in the treatment of autoimmune diseases, infectious diseases, antimicrobial property, canine and feline cancers. The aim of this study is to increase the production level of L-asparaginase by the cloning and expression of Bacillus subtilis L-asparaginase (Asp) gene in Escherichia coli. Materials and methods PCR was used for the amplification of Asp gene of B. subtilis. Asp gene was cloned with the blunt vector pJET1.2 under the control of T7 or lacUV5 promoters. Transformation of both plasmids was done in E. coli JM 107. L-asparaginase was determined in E. coli JM 107 recombinant strains. Results Bacillus Asp gene was amplified using PCR and the primers were deduced from the published ansA sequence. PCR program was optimized. The PCR product (1112 bp DNA fragment containing the Asp gene) was detected, purified, and sequenced. The DNA sequence including the complete Asp CDS sequence was deposited in GenBank (GenBank accession number KJ642620.1). The amplicon was cloned using the blunt vector pJET1.2 under the control of T7 or lacUV5 promoters. The recombinant plasmids containing the Asp gene were transformed and expressed into E. coli JM 107. The expression level of Asp in the recombinant stains was increased up to 22 U/ml, which is 2.5-fold higher than that of E. coli JM 107 wild type. The vector promoters had regulatory effect on L-asparaginase production, where the activity under the control of T7 promoter was increased by 47% compared with that of lacUV5 promoter. Conclusion L-asparaginase production could be improved by cloning and by the expression of its corresponding gene in E. coli. The T7 promoter had a higher regulatory effect on L-asparaginase production level than lacUV5 promoter.

Tạo dòng và biểu hiện interleukin 2 (IL-2) người tái tổ hợp trong Escherichia coli

Immunotherapy using interleukin 2 (IL-2) was approved by FDA for the treatment of some solid tumors and for the combination with AIDS/HIV’s HAART. In order to produce recombinant interleukin 2 with low price, the project was initiated to clone and express IL-2 in Escherichia coli. The il2 gene was amplified by PCR, using the pIDT-IL2 as template with two specific primers (IL2-F and IL2-R) containing BamHI and NdeI sites. The PCR product was digested with BamHI and NdeI then inserted into an expression vector pET-His to construct a recombinant plasmid termed pET-il2 capable of expressing IL-2 under the control of T7 promoter. The recombinant plasmid pET-il2 was transformed into E. coli strain Origami(DE3) to form the Origami(DE3)/pET-il2 clone. This clone was cultured and induced with 0.5 mM IPTG over-expressed IL-2 protein as inclusion body in cytoplasm. The expressing of the target protein was confirmed by SDS-PAGE and Western Blot with anti-IL2 antibody.

Development of a graft inoculation method and a real-time RT-PCR assay for monitoring Tomato chlorosis virus infection in tomato

A graft inoculation method coupled with RT-qPCR was developed for monitoring ToCV infection in tomato plants. Ten seed-grown tomato seedlings were graft inoculated with phloem tissue-containing stem segments from a ToCV-infected tomato plants. Another group of tomato seedling were grafted with similar stem segments from a healthy tomato plant as mock inoculated control. The CP gene of ToCV was cloned under the control of T7 promoter and in vitro synthesized RNA was used as a standard for quantification. Total RNA was isolated from leaf samples of ToCV-inoculated and mock-inoculated control plants before the inoculation and 1–60 days post inoculation (dpi). The presence and the titer of ToCV were determined from all ToCV-inoculated or mock-inoculated control plants by RT-qPCR. After 15 dpi, ToCV was detected in 20–30% of graft-inoculated plants. The infection rate then increased progressively and reached to 70–80% by 60 dpi. Titer of ToCV was at the detectable level at 15 dpi and increased and reached to maximum level by 40 dpi and then started to decrease. The results showed that patch grafting is a simple and efficient method for experimental inoculation of ToCV and can be used as an alternative and/or complementary to vector transmission in the laboratories. The patch grafting could be combined with RT-qPCR and used for infecting and quantitative monitoring of ToCV or other phloem-limited viruses in tomato or in other plants.

Overexpressed recombinant quorum quenching lactonase reduces the virulence, motility and biofilm formation of multidrug-resistant Pseudomonas aeruginosa clinical isolates.

The increasing occurrence of resistance among Pseudomonas aeruginosa clinical isolates necessitates finding alternatives to antibiotics for controlling the infection of such pathogenic bacteria. In this study, lactonase gene ahl-1 from Bacillus weihenstephanensis isolate-P65 was successfully cloned and expressed in Escherichia coli BL21 (DE3) under the control of T7 promoter for utilizing its quorum quenching activity against three multidrug-resistant (MDR) P. aeruginosa clinical isolates. The biological activity of the overexpressed lactonase enzyme (Ahl-1), tested using a synthetic signal and Chromobacterium violaceum CV026 as a biosensor, displayed good catalytic activity using hexanoyl homoserine lactone (HHL) as a substrate and Chromobacterium violaceum (CV026) as a biosensor (77.2 and 133nmmin-1 for the crude and the purified Ahl-lactonase enzymes, respectively). Upon challenging its ability to inhibit the virulence of three MDR P. aeruginosa clinical isolates, recombinant Ahl-1 successfully prevented the accumulation of acylhomoserine lactone signals resulting in a significant reduction in the investigated virulence determinants; protease (from 40 up to 75.5%), pyocyanin (48-75.9%), and rhamnolipids (52.7-63.4%) (P value < 0.05). Ahl-1 also displayed significant inhibitory activities on the swarming motility and biofilm formation of the three tested MDR P. aeruginosa clinical isolates (P value < 0.05). Consequently, Ahl-1 lactonase enzyme in this study is considered a promising therapeutic agent to inhibit P. aeruginosa pathogenicity with no fear of emergence of resistance.

Application of chromosomal gene insertion into Escherichia coli for expression of recombinant proteins

Escherichia coli is the most popular organism used for producing recombinant proteins. However, the expression of recombinant proteins in E.coli sometimes results in the aggregation of proteins as an inclusion body in host cells. In such cases, it is necessary to optimize the refolding conditions to obtain the recombinant protein in its native form. Several techniques, such as reducing the concentration of the induction reagent during E.coli cultivation, have been developed to prevent the formation of inclusion bodies by controlling protein expression levels. In this study, we inserted one copy of a target gene under the control of T7 promoter into the E.coli chromosome using the Red-mediated recombination system. This system enabled soluble expression of the putative d-aminoacylase from Pyrococcus abyssi, which is expressed in an insoluble form following the use of conventional plasmid-based T7 promoter/polymerase systems. The relationship between the number of inserted gene copies and amount of soluble recombinant protein produced was evaluated by multiple insertions of the eGFP gene into the E.coli chromosome. The results revealed that the total expression from the insertion of one copy was around 1/5 that of the pET plasmid system and that expression increased as the inserted gene copy number increased up to five copies.

Optimization of EnBase Fed-Batch Cultivation to Improve Soluble Fraction Ratio of α-Luffin Ribosome Inactivating Protein.

BackgroundThe increase of the protein expression via ribosomal manipulation is one of the suggested cellular mechanisms involved in EnBase fed-batch mode of cultivation. However, this system has not been implemented for cytotoxic proteins.ObjectivesHere, the expression pattern of α-Luffin, a ribosome inactivation protein (RIP) with an innate toxicity, was investigated in EnBase system and the effect of low temperature cultivation on the increase of α-Luffin solubility was determined.Materials and MethodsThe encoding cDNA for mature α-Luffin was synthesized and subcloned into pET28a plasmid under the control of T7 promoter. The E. coli expression yield in EnBase® Flo fed-batch system was compared with traditional batch mode at two temperatures: 25 °C and 30 °C. Sampling was performed at several time intervals and solubility of recombinant-protein was checked on SDS-PAGE in pellet and supernatant samples. The purification of recombinant protein was performed by Ni-NTA column.ResultsIn fed-batch cultivation mode, the early incubation time was desirable at 30 °C whereas the maximum amount of soluble α-Luffin was achieved from the extended protein synthesis period (12 and 24h post induction) at 25 °C.ConclusionsOur founding showed that EnBase had a greater efficacy in producing higher soluble protein ratios compared to batch cultivation growth rate, however for cytotoxic proteins, incubation temperature and time need to be optimized. Owing to the advantages of natural toxins from RIP family for producing anticancer immune-conjugates, well optimization of this protein expression is of importance regarding industrial aspects. The optimized condition proposed here is promising in terms of large scale soluble production of α-Luffin without the need for refolding.

Construction and recombinant expression of Pseudomonas aeruginosa truncated exotoxin A in Escherichia coli.

Pseudomonas aeruginosa exotoxin A (PE) is a bacterial toxin composed of three domains namely: cell binding, translocation and enzymatic domain. The cytotoxic activity of PE is attributed to the enzymatic domain, which inhibits protein synthesis through ADP-ribosylation of EF-2. PE can be genetically modified to fight cancer. In this regard, a truncated and modified form of PE was produced that could be used for more potent immunotoxins. This modified form termed PE38KDEL was completely devoid of cell binding domain and parts of translocation domain II and Ib which are reported to be inessential for cytotoxicity of the toxin. The resultant expressed protein consisted of the essential translocation domain II and catalytic subunit (domain Ib, III). The deletions in the exotoxin A gene for truncated protein production were made via overlapping PCR extension. The amplicon was cloned in pTZ57r-T vector for DNA works and sub cloned in pET22b expression vector. It is demonstrated here that PE38KDEL can be expressed in huge quantities in Escherichia coli by using the recombinant vector PE38KDEL/pET under control of T7 promoter and E. coli host strain BL21 (DE3) CodonPlus. The protein expression was optimized at 0.5 mM IPTG concentration for induction as soon as the OD600 nm reached 0.6 with 6 hours of post induction culturing at 37°C. The recombinant protein was expressed both as soluble and inclusion body forms however the expression of the soluble form was more pronounced.

Molecular characterization and phylogenetic analysis of one Omega-gliadin gene from Aegilops speltoidesl

Gliadins, as the major components of wheat storage proteins, determine the extensibility properties of dough and have important effects on flour processing quality. Wheat related species carries potential storage protein gene resources for quality improvement. In this study, we isolated and characterized the first complete ?-gliadin gene Omega-AS from Aegilops speltoides L. (2n = 2x = 14, SS) by allelic-specific PCR and investigated its phylogenetic relationships among Triticum and Aegilopsspecies. Molecular structure showed that Omega-AS gene consisted of 1122 bp encoding 373 amino acid residues with deduced molecular mass 41379.21 Da. Omega-AS gene was exceptionally rich in prolines and glutamines with fewer methionine and no cysteine. Sequence characterization and epitope analysis showed that three epitopes QQPIPVQPQQ, TQPQQPTPIQ and IQPQQPFPQQ were absent in Omega-AS gene encoded protein, indicating its potential value for wheat quality improvement with less toxic, or no toxic peptides. Phylogenetic analysis revealed that Omega-AS was closely related to gliadin genes of wheat and related species and its divergence from bread wheat was more recently (less than 1.243 MYA). Heterologous expression showed that Omega-AS gene could successfully express with a high level in E. coli under the control of T7promoter. The transcription expression pattern of Omega-AS gene during grain development detected by qRT-PCR revealed that the highest expression level occurred at 17 days post an thesis.

Adhesion control of human umbilical vein endothelial cells using clickable poly(2-oxazoline)-grafted biosynthesized extracellular matrix protein

A bacterial expression host was used for in vivo incorporation of p-azidophenylalanine (p-N3Phe), a phenylalanine (Phe) analog, into an artificial extracellular matrix protein (aECM-CS5-ELF). The host harbors the mutant phenylalanyl-tRNA synthetase (PheRS) which has an enlarged binding pocket, where the Ala294Gly/Thr251Gly mutant PheRS (PheRS**) was expressed under the control of T7 promoters. Biosynthesized aECM-CS5-ELF containing p-N3Phe (aECM-CS5-ELF-N3) was coupled with alkyne-containing poly(2-oxazoline) prepared via ring-opening polymerization of 2-oxazolines (2-methyl-2-oxazoline, 2-ethyl-2-oxazoline, and 2-iso-propyl-2-oxazoline) using methyl triflate (TfOMe) and propiolic acid as the initiator and terminator, respectively. A copper-catalyzed alkyne-azide click reaction was used to graft the poly(2-oxazoline)s onto the aECM. Examination of the solubility in organic and aqueous media, and the lower critical transition temperature (LCST), revealed a dependence on the incorporation ratio of p-N3Phe and graft chain species; the LCST behavior was markedly altered when poly(2-oxazoline) moieties were present as side chains. Circular dichroism measurements indicate that grafting was not responsible for conformational changes, because the conformation was retained both at below and above the LCST. Specific adhesion and subsequent temperature-sensitive detachment of human umbilical vein endothelial cells (HUVECs) onto the cross-linked aECM-CS5-ELF-N3-graft-poly(2-oxazoline) surfaces was also demonstrated.

Molecular cloning and characterization of a novel vip3-type gene from Bacillus thuringiensis and evaluation of its toxicity against Helicoverpa armigera

Vegetative insecticidal proteins (Vips) represent the second generation of insecticidal trans-genes that will complement the Bacillus thuringiensis delta endotoxins in future. A new vip3A gene was cloned from the promising native isolate, B. thuringiensis JK37 obtained from the soils of maize field. The entire coding sequence of the gene (2370 bp) was amplified and cloned into pET28a(+) expression vector. The deduced amino acid sequence of the vip3A gene revealed variation of several amino acid residues with that of the known vip3A genes and this gene was designated as vip3Aa61 by the B. thuringiensis nomenclature committee. The recombinant pET28a(+)–vip3Aa61 was transformed and expressed in Escherichia coli strain BL21 (DE3) under the control of T7 promoter. SDS-PAGE and Western blot analysis confirmed the expression of an 89 kDa protein. Insect bioassays with 2nd instar larvae of Helicoverpa armigera, one of the most notorious pest affecting various crops including cotton and chick pea displayed toxicity. The toxicity of Vip3Aa61 was expressed as mean lethal concentration (LC50), which was 169.63 ng cm−2. The novel vip3Aa gene may be used for the construction of transgenic plants expressing insecticidal protein for the control of lepidopteran insect pests.

Improved antifungal activity of barley derived chitinase I gene that overexpress a 32kDa recombinant chitinase in Escherichia coli host.

Agricultural crops suffer many diseases, including fungal and bacterial infections, causing significant yield losses. The identification and characterisation of pathogenesis-related protein genes, such as chitinases, can lead to reduction in pathogen growth, thereby increasing tolerance against fungal pathogens. In the present study, the chitinase I gene was isolated from the genomic DNA of Barley (Hordeum vulgare L.) cultivar, Haider-93. The isolated DNA was used as template for the amplification of the ∼935 bp full-length chitinase I gene. Based on the sequence of the amplified gene fragment, class I barley chitinase shares 93% amino acid sequence homology with class II wheat chitinase. Interestingly, barley class I chitinase and class II chitinase do not share sequence homology. Furthermore, the amplified fragment was expressed in Escherichia coli Rosetta strain under the control of T7 promoter in pET 30a vector. Recombinant chitinase protein of 35 kDa exhibited highest expression at 0.5 mM concentration of IPTG. Expressed recombinant protein of 35 kDa was purified to homogeneity with affinity chromatography. Following purification, a Western blot assay for recombinant chitinase protein measuring 35 kDa was developed with His-tag specific antibodies. The purified recombinant chitinase protein was demonstrated to inhibit significantly the important phytopathogenic fungi Alternaria solani, Fusarium spp, Rhizoctonia solani and Verticillium dahliae compared to the control at concentrations of 80 μg and 200 μg.

Abstract 4314: Exclusive delivery of mazF in cancer cells by Listeria monocytogenes

Abstract Programmed cell death (PCD), an active process that leads to cell suicide, is a critical mechanism in every organism. MazF, a bacterial ribonuclease protein, can trigger PCD in bacterial cells and also induce Bak-dependent apoptosis in mammalian cells. This bacterial ribonuclease cleaves mRNAs at ACA sequences leading to inhibition of protein synthesis in cells. Hence, we hypothesized that the overexpression of MazF proteins in cancer cells could result in the induction of apoptosis. In the present study, the ACA-less mazF gene was inserted downstream of the Internal Ribosome Entry Site (IRES) and under the control of T7 promoter. The plasmid was electroporated into Listeria monocytogenes harboring pCSA1 that encodes T7 RNA polymerase under the control of the listeria actA promoter. Subsequently, the bacteria were functionalized with Trastuzumab (Herceptin®) to deliver the mazF mRNA into HER2/neu breast cancer cells. The results showed that MazF protein has an ability to induce apoptosis in HER2/neu breast cancer cells. This finding is the first report of the application and delivery of MazF as an anti-cancer agent for the induction of apoptosis in HER2/neu breast cancer cell line. This research suggests cancer therapy that targets only cancer cells but not healthy cells and offers more advantages, e.g., inexpensiveness, target tissue specificity, easy and safe delivery, in comparison to other gene therapy vectors or direct protein administration. Citation Format: Maryam Saffarian, Jeremy Tzeng. Exclusive delivery of mazF in cancer cells by Listeria monocytogenes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4314. doi:10.1158/1538-7445.AM2017-4314

Production and purification of constructed recombinant hirudin in BL21(DE3) strain

Background/Objective: Hirudin, an extract from the leech, has powerful antithrombin activity affecting the blood coagulation pathway, it is the most potent natural inhibitor of thrombin, it binds thrombin with high affinity, so, the aim of this study was to build hirudin gene by overlapping extension PCR then cloning and expression in BL21(DE3) strain.Methods: Hirudin gene constructed with four modified primers then the final product amplified by two primers named as A, B by using overlapping extension PCR, for gene expression, BL21(DE3) strain was used under the control of T7 promoter in pET-16b vector and for hirudin production, LB broth medium was used as fermentation medium. Hirudin protein purified at first by (Immobilized metal affinity chromatography) IMAC, then this protein was dialysis and treated with factor Xa to eliminate His-tag. Then hirudin purified by DEAE sepharose and SP sepharose column, the concentration of protein determined by ELISA, furthermore the activity evaluated by thrombin titration and activated partial thromboplastin time (APPT) test.Results: Hirudin gene constructed in two round PCR first round produced two products (product1 117 bp while product 2,114 bp) the second-round PCR gave the final product 213 bp. The resulted band from gel electrophoresis for constructed vector pET-16b-HirudinS was (5,901 bp). The analysis on 15% SDS-PAGE for the SP sepharose column illustrated the hirudinS protein band with size about ~10.8. Concentration of produced hirudin within its solution reached to 1.75 ng, thrombin titration method showed that the hirudin protein required 300 µl from thrombin to clot, also, APPT test showed that hirudin elongated clotting time to 7min in comparison with 6min for aspirin and the statistical analysis results for APPT test illustrated that there was no significant difference between hirudin and aspirin.Conclusion: This study approved that overlapping extension PCR is a good strategy for building hirudin gene and it’s successfully expressed in BL21(DE3) strain.

Construction of the plasmid-free strain for human growth hormone production.

The E.coli strain, overproducing human growth hormone (hGH) was made by integration of the hGH gene under the control of T7 promoter into the chromosomal LacZ gene of BL21(DE3) via lambda Red recombineering. The strain gave higher productivity (50mg·L(-1)·OD550(-1)) and better growth characteristics than the corresponding strain in which the same hGH expression cassette was placed in a plasmid. The protein produced by the plasmid-free strain was purified and characterized to be hGH. The results demonstrates that a plasmid-free recombinant strain having a single-copy gene expression cassette in the chromosome could provide better gene activity regulation, higher productivity, superior growth characteristics, as well as more stringent control of the gene sequence invariance than a plasmid-based strain.

Development of the intein-mediated method for production of recombinant thymosin β4 from the acetylated in vivo fusion protein

Thymosin β4 is a 43 amino acid long peptide with an acetylated N-terminal serin that has a high potential as a remedy for healing ulcers, wounds and burns. Although protein biosynthesis offers attractive opportunities in terms of a large-scale production, currently thymosin β4 is mainly produced by chemical synthesis. The problems that hinder the successful commercialization of the biotechnological approach are associated with the small peptides expression and N-terminal acetylation. This work presents an innovative biotechnological method for thymosin β4 production that employs the peptide acetylation in vivo. A genetically engineered construct was created, where the Tβ4 coding sequence fused with the intein Mxe GyrA sequence and chitin-binding domain was combined with the acetyltransferase coding sequence to form a polycistronic construct under a stringent control of T7 promoter. This plasmid construct provided for the expression of the Tβ4-intein fusion protein. In the process of the post-translational modification in vivo formyl methionine was completely removed from the target peptide N-terminus and followed by the Tβ4 precursor N-terminal acetylation. The use of the intein-mediated expression system made it possible to extract thymosin β4 in only 2 chromatographic runs. The method is straightforward to implement and scale up.

Cloning, characterization and expression of a novel haplotype cry2A-type gene from Bacillus thuringiensis strain SWK1, native to Himalayan valley Kashmir

Bacillus thuringiensis (Bt) is a gram positive bacterium which is effectively being used in pest management strategies as an eco-friendly bioinsecticide. In the present study a new cry2A gene was cloned from a promising indigenous B. thuringiensis SWK1 strain previously characterized for its toxicity against Spodoptera litura and Helicoverpa armigera larvae. The nucleotide sequence of the cloned cry2A gene pointed out that the open reading frame has 1902 bases encoding a polypeptide of 634 amino acid residues with a probable molecular weight of 70kDa. Homology comparisons showed that the deduced amino acid sequence of Cry2A had a similarity of 94% compared to that of the known Cry2Aa protein in the NCBI database and this gene has been named as cry2Al1 by the B. thuringiensis δ-endotoxin Nomenclature Committee. cry2Al1 was ligated into pET 22b vector and expressed in Escherichia coli BL21 (DE3) pLysS under the control of T7 promoter induced by isopropyl-beta-d-thiogalactopyranoside (IPTG). SDS-PAGE analysis confirmed the expression of cry2Al1 as ∼65kDa protein. Insect pest bioassays with neonate larvae of S. litura and H. armigera showed that the purified Cry2Al1 are toxic to S. litura and H. armigera with LC50 2.448μg/ml and H. armigera with 3.374μg/ml respectively.

Development and characterization of reverse genetics system for the Indian West Nile virus lineage 1 strain 68856

Our previous studies on West Nile virus (WNV) strains isolated from human patients in India suggested substantial variation at the genetic level reflecting their variable pathogenesis. This study describes the development of reverse genetics system for a neurovirulent WNV isolate 68856 and its characterization. Full length viral cDNA was cloned into bacterial artificial chromosome (BAC) under the transcription control of T7 promoter. The RNA transcripts obtained by in vitro transcription were infectious in mammalian cells upon transfection. Cytopathic effect caused by synthetic RNA transcripts in mammalian cells, detection of cell associated viral protein after transfection and recovery of genetic markers in the progeny virus genome marked the successful development of reverse genetics system for WNV. Replication potential and plaque morphology of newly expressed virus along with its antigenic cross reactivity with the parental virus suggests synthesis of biologically identical replicative virus. Comparative neuropathogenesis studies in murine model indicated that the three genetic changes occurred in the recombinant virus during in vitro transcription has no impact on viral pathogenesis. The stable infectious cDNA clone generated from the neurovirulent Indian WNV strain will serve as a valuable experimental tool to study the viral factors contributing towards pathogenesis, host–virus interaction and immune evasion.