Application of the E. coli trp promoter

Recombinant expression, downstream optimization, and therapeutic evaluation of recombinant human interleukin-37 for cancer therapy

Interleukin-37 is a cytokine with potent immunosuppressive properties that has been shown to have potential to treat autoimmune and chronic inflammatory diseases, as well as certain types of cancer. IL-37 is a 19 kDa protein which interacts with proteins in receptor-dependent and receptor-independent pathways. The expression of the IL-37 protein cloned into the pET-28a vector was optimized in Rosetta 2(DE3) after comparing its expression with Rosetta-gami 2(DE3) and Rosetta 2(DE3) pLysS, which was then used for the large-scale production of IL-37. IMAC purification of IL-37 yielded > 97% pure 0.9 mg/mL protein from auto-induced fermentation. The IC50 value of IL-37 was < 1 µM, which was similar to that of doxorubicin, and proliferation of > 80% of all cancer cells was inhibited by 100 µg/mL of IL-37 protein. IL-37 may be a promising theragnostic target for cancer due to its comparable IC50 value with that of doxorubicin.

Directed evolution of highly sensitive and stringent choline-induced gene expression controllers

Gene expression controllers are useful tools for microbial production of recombinant proteins and valued bio-based chemicals. Despite its usefulness, they have rarely been applied to the practical industrial bioprocess, due to the lack of systems that meets the three requirements: low cost, safety, and tight control, to the inducer molecules. Previously, we have developed the high-spec gene induction system controlled by safe and cheap inducer choline. However, the system requires relatively high concentration (~100 mM) of choline to fully induce the gene under control. In this work, we attempted to drastically improve the sensitivity of this induction system to further reduce the induction costs. To this end, we devised a simple circuit which couples gene induction system with positive-feedback loop (P-loop) of choline importer protein BetT. After the tuning of translation level of BetT (strength of the P-loop) and deletion of endogenous betI (noise sources), highly active yet stringent control of gene expression was achieved using about 100 times less amount of inducer molecules. The choline induction system developed in this study has the lowest basal expression, the lowest choline needed to be activated, and the highest amplitude of induction as the highest available promoter such as those known as PT5 system. With this system, one can tightly control the expression level of genes of interest with negligible cost for inducer molecule, which has been the bottleneck for the application to the large-scale industrial processes.

Thermoinducible expression system for producing recombinant proteins in Escherichia coli: advances and insights

Recombinant protein (RP) production from Escherichia coli has been extensively studied to find strategies for increasing product yields. The thermoinducible expression system is commonly employed at the industrial level to produce various RPs which avoids the addition of chemical inducers, thus minimizing contamination risks. Multiple aspects of the molecular origin and biotechnological uses of its regulatory elements (pL/pR promoters and cI857 thermolabile repressor) derived from bacteriophage λ provide knowledge to improve the bioprocesses using this system. Here, we discuss the main aspects of the potential use of the λpL/pR-cI857 thermoinducible system for RP production in E. coli, focusing on the approaches of investigations that have contributed to the advancement of this expression system. Metabolic and physiological changes that occur in the host cells caused by heat stress and by RP overproduction are also described. Therefore, the current scenario and the future applications of systems that use heat to induce RP production is discussed to understand the relationship between the activation of the bacterial heat shock response, RP accumulation, and its possible aggregation to form inclusion bodies.

An autoinducible trp-T7 expression system for production of proteins and biochemicals in Escherichia coli

Inducible expression systems can be applied to control the expression of proteins or biochemical pathways in cell factories. However, several of the established systems require the addition of expensive inducers, making them unfeasible for large‐scale production. Here, we establish a genome integrated trp‐T7 expression system where tryptophan can be used to control the induction of a gene or a metabolic pathway. We show that the initiation of gene expression from low‐ and high‐copy vectors can be tuned by varying the initial concentration of tryptophan or yeast extract, and that expression is tightly regulated and homogenous when compared with the commonly used lac‐T7 system. Finally, we apply the trp‐T7 expression system for the production of l‐serine, where we reach titers of 26 g/L in fed‐batch fermentation.

Prophage protein RacR activates lysozyme LysN, causing the growth defect of E. coli JM83

Prophage enriched the prokaryotic genome, and their transcriptional factors improved the protein expression network of the host. In this study, we uncovered a new prophage-prophage interaction in E. coli JM83. The Rac prophage protein RacR (GenBank accession no. AVI55875.1) directly activated the transcription of φ80dlacZΔM15 prophage lysozyme encoding gene 19 (GenBank accession no. ACB02445.1, renamed it lysN, lysozyme nineteen), resulting in the growth defect of JM83. This phenomenon also occurred in DH5α, but not in BL21(DE3) and MG1655 due to the genotype differences. However, deletion of lysN could not completely rescued JM83 from the growth arrest, indicating that RacR may regulate other related targets. In addition, passivation of RacR regulation was found in the late period of growth of JM83, and it was transmissible to daughter cells. Altogether, our study revealed part of RacR regulatory network, which suggested some advanced genetic strategies in bacteria.

Heterologous Expression and Isolation of Influenza A Virus Nuclear Export Protein NEP

Influenza A virus nuclear export protein NEP (NS2, 14.4 kDa) plays a key role in various steps of the virus life cycle. Highly purified protein preparations are required for structural and functional studies. In this study, we designed a series of Escherichia coli plasmid constructs for highly efficient expression of the NEP gene under control of the constitutive trp promoter. An efficient method for extraction of NEP from inclusion bodies based on dodecyl sulfate treatment was developed. Preparations of purified NEP with either N- or C-terminal (His)₆-tag were obtained using Ni-NTA agarose affinity chromatography with yield of more than 20 mg per liter of culture. According to CD data, the secondary structure of the proteins matched that of natural NEP. A high propensity of NEP to aggregate over a wide range of conditions was observed.

Obtention and characterization of the recombinant simian Interleukin-15 in Escherichia coli for the preclinical assessment of an IL-15-based therapeutic vaccine

Recombinant simian IL-15 (siIL-15) was obtained for the preclinical assessment of an anti-human IL-15 vaccine. For this purpose, the cDNA from peripheral blood mononuclear cells of a Macaca fascicularis monkey was cloned into a pIL-2 vector. The siIL-15 was expressed in Escherichia coli strain W3110 as an insoluble protein which accounted for 13% of the total cellular proteins. Inclusion bodies were solubilized in an 8 M urea solution, which was purified by ion exchange and reverse phase chromatography up to 92% purity. The protein identity was validated by electrospray ionization-mass spectrometry, confirming the presence of the amino acids which distinguish the siIL-15 from human IL-15. The purified siIL-15 stimulates the proliferation of cytotoxic T-lymphocytes line (CTLL)-2 and Kit 225 cells with EC₅₀ values of 3.1 and 32.5 ng/mL, respectively. Antisera from modified human IL-15-immunized macaques were reactive to human and simian IL-15 in enzyme-linked immunosorbent assays. Moreover, the anti-human IL-15 antibodies from immune sera inhibited siIL-15 activity in CTLL-2 and Kit 225 cells, supporting the activity and purity of recombinant siIL-15. These results indicate that the recombinant siIL-15 is biologically active in two IL-15-dependent cell lines, and it is also suitable for the preclinical evaluation of an IL-15-based therapeutic vaccine.

Molecular cloning of Reteplase and its expression in E. coli using tac promoter

BACKGROUND AND AIMS

This study aimed to clone and express the reteplase cDNA, a thrombolytic agent used for the treatment of acute myocardial infarction and stroke, in E. coli, utilizing tac promoter for its expression.

MATERIALS AND METHODS

Reteplase cDNA was amplified by polymerase chain reaction (PCR) with designed primers. The product was then cloned into pTZ57R plasmid. The cloned cDNA was digested out and ligated into pGEX-5x-1 expression vector. The presence of the insert was confirmed by restriction digestion. By using 0.2, 0.5 and 1 mM isopropyl beta-D thiogalactopyranoside (IPTG), expression of reteplase was induced in E. coli TOP10 cells and analyzed by SDS-PAGE.

RESULTS

Electrophoresis of PCR product and also double digested recombinant pTZ57R plasmid, also, pGEX-5x-1 vector, showed a 1068bp band of reteplase. SDS-PAGE analysis showed a 60 KDa band of protein product induced with different concentrations of IPTG.

CONCLUSION

In the present study, reteplase cDNA was successfully cloned and expressed using tac promoter. This vector will be used for the optimization of the expression of reteplase in E. coli.

Scale-up of recombinant Opc protein production in Escherichia coli for a meningococcal vaccine

Opc is an outer membrane protein from Neisseria meningitidis present in meningococcal vaccine preparations. The opc gene, codifying for this protein, was cloned in to Escherichia coli and the Opc protein was expressed under the control of a tryptophan promoter. The recombinant strain was grown in batch cultures. Opc was expressed as inclusion bodies at about 32% of the total cellular protein. We examined the scale-up culture conditions for the production of the recombinant Opc. The scale-up process was performed from 1.5 l to 50 l culture, using first, the constant power per unit of volume (P/V) as main scaling criteria, and then the oxygen mass transfer coefficient (K(L)a) scaling criteria to adjust the optimal aeration conditions. A final productivity of 52 mgl(-1)h(-1) was obtained at the 50l culture scale compared with the 49 mgl(-1)h(-1) productivity at 1.5l laboratory scale.