Cloning, expression, and purification of a synthetic human growth hormone in Escherichia coli using response surface methodology

Prokaryotic Expression, Purification, and Antibacterial Activity of the Hepcidin Peptide of Crescent Sweetlips (Plectorhinchus cinctus)

The hepcidin peptide of crescent sweetlips (Plectorhinchus cinctus) is a cysteine-rich, cationic antimicrobial peptide that plays a crucial role in the innate immune system's defense against invading microbes. The aim of this study was to identify the optimal parameters for prokaryotic expression and purification of this hepcidin peptide and characterize its antibacterial activity. The recombinant hepcidin peptides were expressed in Escherichia coli strain Arctic Express (DE3), with culture and induction conditions optimized using response surface methodology (RSM). The obtained hepcidin peptides were then purified before tag cleavage, and their antibacterial activity was determined. The obtained results revealed that induction temperature had the most significant impact on the production of soluble recombinant peptides. The optimum induction conditions were determined to be an isopropylthio-β-galactoside (IPTG) concentration of 0.21 mmol/L, induction temperature of 18.81 °C, and an induction time of 16.01 h. Subsequently, the recombinant hepcidin peptide was successfully purified using Ni-IDA affinity chromatography followed by SUMO protease cleavage. The obtained hepcidin peptide (without His-SUMO tag) demonstrated strong antimicrobial activity in vitro against V. parahaemolyticus, E. coli, and S. aureus. The results showed prokaryotic (E. coli) expression is a feasible way to produce the hepcidin peptide of crescent sweetlips in a cost-effective way, which has great potential to be used as an antimicrobial agent in aquaculture.

Cloning, Expression, and Purification of the Human Synthetic Survivin Protein in Escherichia coli Using Response Surface Methodology (RSM)

Survivin is one of the novel members of the apoptosis inhibitor protein family in humans. The main activity of the Survivin protein is to suppress caspases activity resulting in negative regulation of apoptosis. Survivin protein can be a potential target for the treatment of cancers between cancerous and normal cells. In the present research, the synthetic Survivin gene with PelB secretion signal peptide was cloned into a prokaryotic expression vector pET21a. The recombinant plasmid pET21a-PelB-Surv was expressed in Escherichia coli (E.coli) BL21, and the relative molecular mass of expressed protein was calculated 34,000 g/mol, approximately. The recombinant protein was purified through chromatography column and characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Response surface methodology (RSM) was used to design 20 experiments for optimization of IPTG concentration, post-induction period, and cell density of induction (OD600). The optimum levels of the selected parameters were successfully determined to be 0.28 mM for IPTG concentration, 10 h for post-induction period, and 3.40768 for cell density (OD600). These findings resulted in 4.14-fold increases in the Survivin production rate of optimum expression conditions (93.6363 mg/ml).

Generation of a recombinant version of a biologically active cell-permeant human HAND2 transcription factor from E. coli

Transcription factor HAND2 has a significant role in vascularization, angiogenesis, and cardiac neural crest development. It is one of the key cardiac factors crucial for the enhanced derivation of functional and mature myocytes from non-myocyte cells. Here, we report the generation of the recombinant human HAND2 fusion protein from the heterologous system. First, we cloned the full-length human HAND2 gene (only protein-coding sequence) after codon optimization along with the fusion tags (for cell penetration, nuclear translocation, and affinity purification) into the expression vector. We then transformed and expressed it in Escherichia coli strain, BL21(DE3). Next, the effect (in terms of expression) of tagging fusion tags with this recombinant protein at two different terminals was also investigated. Using affinity chromatography, we established the one-step homogeneous purification of recombinant human HAND2 fusion protein; and through circular dichroism spectroscopy, we established that this purified protein had retained its secondary structure. We then showed that this purified human protein could transduce the human cells and translocate to its nucleus. The generated recombinant HAND2 fusion protein showed angiogenic potential in the ex vivo chicken embryo model. Following transduction in MEF2C overexpressing cardiomyoblast cells, this purified recombinant protein synergistically activated the α-MHC promoter and induced GFP expression in the α-MHC-eGFP reporter assay. Prospectively, the purified bioactive recombinant HAND2 protein can potentially be a safe and effective molecular tool in the direct cardiac reprogramming process and other biological applications.

Facile expression and purification of active human growth hormone in E. coli by a cleavable self-aggregating tag scheme

Human growth hormone (hGH) plays an important role in growth control, growth promotion, cell development, and regulation of numerous metabolic pathways in the human body and has been approved by the U.S. FDA for the treatment of several human dysfunctions. Over-expression of recombinant hGH (rhGH) affords a misfolded form in cytoplasm of Escherichia coli, and the refolding step required to obtain active rhGH greatly affects its production costs. Herein, the cleavable self-aggregating tag (cSAT) scheme was used for the expression and purification of rhGH in E. coli. Four aggregating tags (L₆KD/α3-peptide/EFK8/ELK16) successfully drove rhGH into active protein aggregates. After the Mxe GyrA intein-mediated cleavage, 2.8-21.4 μg rhGH/mg wet cell weight was obtained at laboratory scale, of which the L₆KD fusion achieved the highest rhGH yield. The further refined rhGH maintained 92% of the bioactivity compared to commercial rhGH. The self-assembling of the aggregating tag might physically separate the hGH polypeptide chains, which in turn was beneficial to its folding into the active form. This study provided a simple and cost-effective approach for active rhGH production, and suggested an opportunity for improve folding of recombinant proteins in E. coli.

Identification of Optimal Expression Parameters and Purification of a Codon-Optimized Human GLIS1 Transcription Factor from Escherichia coli

GLIS1 has multiple roles in embryonic development and in deriving induced pluripotent stem cells by aiding signaling pathways and chromatin assembly. An inexpensive and simple method to produce human GLIS1 protein from Escherichia coli (E. coli) is demonstrated in this study. Various parameters such as codon usage bias, E. coli strains, media, induction conditions (such as inducer concentration, cell density, time, and temperature), and genetic constructs were investigated to obtain soluble expression of human GLIS1 protein. Using identified expression conditions and an appropriate genetic construct, the human GLIS1 protein was homogeneously purified (purity > 90%) under native conditions. Importantly, the purified protein has upheld a stable secondary structure, as demonstrated by circular dichroism spectroscopy. To the best of our knowledge, this is the first study to report the ideal expression conditions of human GLIS1 protein in E. coli to achieve soluble expression and purification under native conditions, upholding its stable secondary structure post-purification. The biological activity of the purified GLIS1 fusion protein was further assessed in MDA-MB-231 cells. This biologically active human GLIS1 protein potentiates new avenues to understand its molecular mechanisms in different cellular functions in various cancers and in the generation of induced pluripotent stem cells.

Optimization of Expression and Purification of Schistosoma mansoni Antigens in Fusion with Rhizavidin

Schistosomiasis causes significant morbidity and mortality. Vaccine efforts to date indicate the need to increase the immunogenicity of Schistosoma antigens. The multiple antigen-presenting system, whereby proteins are genetically fused to rhizavidin and affinity linked to biotinylated templates, enables the generation of robust immune responses. The objective of this work was to express and purify the S. mansoni antigens, SmTSP-2 and SmCD59.2, in fusion with rhizavidin. The fusion with rhizavidin greatly decreased the expression level of rSmTSP-2, but not rSmCD59.2, and both were expressed in the insoluble fraction, requiring optimization of culture conditions. Evaluation of different E. coli strains and media showed that BL21-DE3 cultured in Terrific Broth provided the highest expression levels of both proteins. Investigation of a range of time and temperature of induction showed that E. coli strains expressing rRzv:SmTSP-2 and rRzv:SmCD59.2 showed the highest protein production at 23 °C for 15 h. Recombinant proteins were purified by a single step of affinity chromatography allowing isolation of these proteins in high concentration and purity. The optimization process increased final soluble protein yield of rRzv:SmTSP-2 by fourfold and rRzv:SmCD59.2 by tenfold, providing ~ 20 mg/L of each protein. Optimized fusion protein production will allow antigen use in biotin–rhizavidin affinity platforms.

Soluble expression, purification, and secondary structure determination of human MESP1 transcription factor

Transcription factor MESP1 is a crucial factor regulating cardiac, hematopoietic, and skeletal myogenic development. Besides, it also contributes to the generation of functional cardiomyocytes. Here, we report the soluble expression and purification of the full-length human MESP1 protein from the heterologous system, which can be delivered into the target mammalian cells. To generate this biological macromolecule, we cloned its codon-optimized gene sequence fused to a nuclear localization sequence, a cell-penetrating peptide, and a His-tag into the protein expression vector and expressed in the bacterial system (E. coli strain BL21(DE3)). Subsequently, we have screened and identified the optimal expression parameters to obtain this recombinant fusion protein in soluble form from E. coli and examined its expression concerning the placement of fusion tags at either terminal. Further, we have purified this recombinant fusion protein to homogeneity under native conditions. Notably, this purified fusion protein has maintained its secondary structure after purification, primarily comprising α-helices and random coils. This molecular tool can potentially replace its genetic and viral forms in the cardiac reprogramming of fibroblasts to induce a cardiac transcriptional profile in an integration-free manner and elucidating its role in various biological processes and diseases. KEY POINTS: • Screening of the suitable gene construct was performed and identified. • Screening of optimal expression conditions was performed and identified. • Native purification of recombinant human MESP1 protein from E. coli was performed. • Recombinant MESP1 protein has retained its secondary structure after purification.

Generation of a Recombinant Stem Cell-Specific Human SOX2 Protein from Escherichia coli Under Native Conditions

The stem cell-specific SOX2 transcription factor is critical for early embryonic development and the maintenance of embryonic and neural stem cell identity. It is also crucial for the generation of induced pluripotent and neural stem cells, thus providing immense prospect in patient-specific therapies. Here, we report soluble expression and purification of human SOX2 protein under native conditions from a bacterial system. To generate this macromolecule, we codon-optimized the protein-coding sequence and fused it to a nuclear localization signal, a protein transduction domain, and a His-tag. This was then cloned into a protein expression vector and was expressed in Escherichia coli. Subsequently, we have screened and identified the optimal expression conditions to obtain recombinant fusion protein in a soluble form and studied its expression concerning the position of fusion tags at either terminal. Furthermore, we purified two versions of recombinant SOX2 fusion proteins to homogeneity under native conditions and demonstrated that they maintained their secondary structure. This molecular tool can substitute genetic and viral forms of SOX2 to facilitate the derivation of integration-free induced pluripotent and neural stem cells. Furthermore, it can be used in elucidating its role in stem cells, various cellular processes and diseases, and for structural and biochemical studies.

Codon Optimization, Cloning, Expression, Purification, and Secondary Structure Determination of Human ETS2 Transcription Factor

Transcription factor ETS2 regulates genes involved in development, differentiation, angiogenesis, proliferation, and apoptosis. In addition, it is one of the core reprogramming factors responsible for the generation of human cardiomyocytes from adult somatic cells. In this study, we report the heterologous expression of human ETS2 in E. coli to produce a highly pure recombinant protein. To accomplish this, the codon-optimized 1507 bp coding sequence of the human ETS2 gene in fusion with a His-tag, a cell-penetrating peptide, and a nuclear localization sequence was cloned in the protein expression vector and transformed into E. coli strain BL21(DE3) for expression. The recombinant protein was purified to homogeneity under native conditions using immobilized metal ion affinity chromatography, and its identity was confirmed by Western blotting with an ETS2 antibody. Using far-UV circular dichroism spectroscopy, we have demonstrated that the recombinant protein has retained its secondary structure, predominantly comprising of random coils and β-sheets. Prospectively, this biological recombinant ETS2 protein can substitute viral and genetic forms of ETS2 in a cell reprogramming process to facilitate the generation of clinical-grade cells. It can also be used to investigate its molecular role in various biological processes and diseases and for biochemical and structural studies.

Optimization and scale-up production of Zika virus ΔNS1 in Escherichia coli: application of Response Surface Methodology

Diagnosing Zika virus (ZIKV) infections has been challenging due to the cross-reactivity of induced antibodies with other flavivirus. The concomitant occurrence of ZIKV and Dengue virus (DENV) in endemic regions requires diagnostic tools with the ability to distinguish these two viral infections. Recent studies demonstrated that immunoassays using the C-terminal fragment of ZIKV NS1 antigen (ΔNS1) can be used to discriminate ZIKV from DENV infections. In order to be used in serological tests, the expression/solubility of ΔNS1 and growth of recombinant E. coli strain were optimized by Response Surface Methodology. Temperature, time and IPTG concentration were evaluated. According to the model, the best condition determined in small scale cultures was 21 °C for 20 h with 0.7 mM of IPTG, which predicted 7.5 g/L of biomass and 962 mg/L of ΔNS1. These conditions were validated and used in a 6-L batch in the bioreactor, which produced 6.4 g/L of biomass and 500 mg/L of ΔNS1 in 12 h of induction. The serological ELISA test performed with purified ΔNS1 showed low cross-reactivity with antibodies from DENV-infected human subjects. Denaturation of ΔNS1 decreased the detection of anti-ZIKV antibodies, thus indicating the contribution of conformational epitopes and confirming the importance of properly folded ΔNS1 for the specificity of the serological analyses. Obtaining high yields of soluble ΔNS1 supports the viability of an effective serologic diagnostic test capable of differentiating ZIKV from other flavivirus infections.

Identification and characterization of a sterically robust phenylalanine ammonia-lyase among 481 natural isoforms through association of in silico and in vitro studies

The enzyme phenylalanine ammonia lyase (PAL) is of special importance for the treatment of phenylketonuria patients. The aim of this study was to find a stable recombinant PAL with suitable kinetic properties among all natural PAL producing species using in silico and experimental approaches. To find such a stable PAL among 481 natural isoforms, 48,000 of 3-D models were predicted using the Modeller 9.10 program and evaluated by Ramachandran plot. Correlation analysis between Ramachandran plot and the energy of different thermodynamic components indicated that this plot could be an appropriate tool to predict protein stability. Hence, PAL6 from Lotus japonicus (LjPAL6) was selected as a stable isoform. Molecular dynamic (MD) simulation for 50 ns and docking has been conducted for LjPAL6-phenylalanine complex. The best PAL-phenylalanine frame was selected by re-docking with l-phenylalanine (L-Phe) and root-mean-square deviation (RMSD) value. MD simulation showed that the complex has a good stability, depicted by the low RMSD value, binding free energy and hydrogen bindings. Docking results showed that LjPAL6 has a high affinity toward l-Phe according to the low level of binding free energy. By overexpressing Ljpal6 in E. coli BL21, a total of 33.5 mg/l of protein was obtained, which has been increased to 83.7 mg/l via the optimization of LjPAL6 production using response surface methodology. The optimal pH and temperature were 8.5 and 50 °C, respectively. LjPAL6 showed a specific activity of 42 nkat/mg protein, with K_m, K_cat and K_cat/K_m values of 0.483 mM, 7 S^-1 and 14.5 S^-1 mM^-1 for l-phe, respectively. In conclusion, finding models with the most reasonable stereo-chemical quality and lowest numbers of steric clashes would result in easier folding. Hence, in silico analyses of bulk data from natural origin will lead one to find an optimal model for in vitro studies and drug design.

High purity recombinant human growth hormone (rhGH) expression in Escherichia coli under phoA promoter

ABSTACT Recombinant human Growth Hormone (rhGH) is an important protein for human growth and is in high demand in clinics. Hence, it is necessary to develop an efficient fermentation process to produce highly pure rhGH. In this study, rhGH was expressed in Escherichia coli under alkaline phosphatase (phoA) promoter. The cultivation conditions for high expression level and purity of rhGH were investigated. The best initial phosphate concentration for rhGH expression, out of the 4 levels of initial phosphate concentration tests performed, was 12.6 mmol/L. Subsequently, 2 fed-batch cultivations under low dissolved oxygen (DO) (0% - 10%) and high DO (20% - 30%) conditions were carried out. High purity rhGH (92%) was obtained from 20% - 30% DO-stat cultivation, although the biomass did not show any significant difference. In summary, this research provided an efficient fermentation process for high purity rhGH production from E. coli under phoA promoter, which can lower the production and purification costs for large-scale production of rhGH.

Identification of Novel Components Influencing Colonization Factor Antigen I Expression in Enterotoxigenic Escherichia coli

Colonization factors (CFs) mediate early adhesion of Enterotoxigenic Escherichia coli (ETEC) in the small intestine. Environmental signals including bile, glucose, and contact with epithelial cells have previously been shown to modulate CF expression in a strain dependent manner. To identify novel components modulating CF surface expression, 20 components relevant to the intestinal environment were selected for evaluation. These included mucin, bicarbonate, norepinephrine, lincomycin, carbon sources, and cations. Effects of individual components on surface expression of the archetype CF, CFA/I, were screened using a fractional factorial Hadamard matrix incorporating 24 growth conditions. As most CFs agglutinate erythrocytes, surface expression was evaluated by mannose resistant hemagglutination. Seven components, including porcine gastric mucin, lincomycin, glutamine, and glucose were found to induce CFA/I surface expression in vitro in a minimal media while five others were inhibitory, including leucine and 1,10-phenanthroline. To further explore the effect of components positively influencing CFA/I surface expression, a response surface methodology (RSM) was designed incorporating 36 growth conditions. The optimum concentration for each component was identified, thereby generating a novel culture media, SP1, for CFA/I expression. CFs closely related to CFA/I, including CS4 and CS14 were similarly induced in SP1 media. Other epidemiologically relevant CFs were also induced when compared to the level obtained in minimal media. These results indicate that although CF surface expression is complex and highly variable among strains, the CF response can be predicted for closely related strains. A novel culture media inducing CFs in the CF5a group was successfully identified. In addition, mucin was found to positively influence CF expression in strains expressing either CFA/I or CS1 and CS3, and may function as a common environmental cue.