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Indirect optimization of staphylokinase expression level in dicistronic auto-inducible system.

ABSTRACT: Design of experiment (DOE) is a statistical approach for designing, performing, and interpreting a large set of data with the minimum number of tests. In our previous study, we developed a novel Hsp27 SILEX system for production of recombinant proteins. In the present study, we optimized indirectly the most effective factors including inoculation load, self-induction temperature, and culture media on autoinduction of staphylokinase (SAK) expression using RSM methodology and fluorometry. The expression level of SAK was assayed at different runs after 6 h incubation at 90 rpm. The results indicated all parameters significantly affect the SAK expression level (p < 0.05). The optimum expression condition was obtained with an inoculation load of 0.05, a temperature of 25 °C, and TB culture medium. The analysis of variance with a R² value of 0.91 showed that a quadratic model well described this prediction (p < 0.05). Applying the optimized condition led to an approximately fourfold increase in the SAK expression level (from 1.3 to 5.2 µg/ml). Moreover, the recombinant protein was purified using immobilized metal affinity chromatography and the activity was also confirmed by semi-quantitative caseinolytic method.

SUBMITTER: Shariati FS

PROVIDER: S-EPMC9500143 | biostudies-literature | 2022 Sep

REPOSITORIES: biostudies-literature

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Indirect optimization of staphylokinase expression level in dicistronic auto-inducible system.

Shariati Fatemeh Sadat FS Keramati Malihe M Cohan Reza Ahangari RA

AMB Express 20220922 1

Design of experiment (DOE) is a statistical approach for designing, performing, and interpreting a large set of data with the minimum number of tests. In our previous study, we developed a novel Hsp27 SILEX system for production of recombinant proteins. In the present study, we optimized indirectly the most effective factors including inoculation load, self-induction temperature, and culture media on autoinduction of staphylokinase (SAK) expression using RSM methodology and fluorometry. The expr ...[more]

PMID: 36138332

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Project description:BackgroundAfter many years of intensive research, it is generally assumed that no universal expression system can exist for high-level production of a given recombinant protein. Among the different expression systems, the inducible systems are the most popular for their tight regulation. However, induction is in many cases less favorable due to the high cost and/or toxicity of inducers, incompatibilities with industrial scale-up or detrimental growth conditions. Expression systems using autoinduction (or self-induction) prove to be extremely versatile allowing growth and induction of recombinant proteins without the need to monitor cell density or add inducer. Unfortunately, almost all the actual auto inducible expression systems need endogenous or induced metabolic changes during the growth to trigger induction, both frequently linked to detrimental condition to cell growth. In this context, we use a simple modular approach for a cell density-based genetic regulation in order to assemble an autoinducible recombinant protein expression system in E. coli.ResultThe newly designed pLAI expression system places the expression of recombinant proteins in Escherichia coli under control of the regulatory genes of the lux regulon of Vibrio fischeri's Quorum Sensing (QS) system.The pLAI system allows a tight regulation of the recombinant gene allowing a negligible basal expression and expression only at high cell density. Sequence optimization of regulative genes of QS of V. fischeri for expression in E. coli upgraded the system to high level expression. Moreover, partition of regulative genes between the plasmid and the host genome and introduction of a molecular safety lock permitted tighter control of gene expression.ConclusionCoupling gene expression to cell density using cell-to-cell communication provides a promising approach for recombinant protein production. The system allows the control of expression of the target recombinant gene independently from external inducers or drastic changes in metabolic conditions and enabling tight regulation of expression.

Project description:Photoautotrophic microalgae offer a great potential as novel hosts for efficient recombinant protein production. Nannochloropsis oceanica produces an extraordinarily high content of polyunsaturated fatty acids, and its robust growth characteristics, published genome sequence and efficient nuclear transformation make N. oceanica a promising candidate for biotechnological applications. To establish a robust and flexible system for recombinant protein production, we cloned six endogenous, potentially constitutive or inducible promoters from N. oceanica strain CCMP1779 and investigated their strength using monomeric Venus as reporter gene. Microscopic pre-screening of individual transformants revealed that the promoters of elongation factor (EF), tubulin (TUB) and nitrate reductase (NR) enabled high reporter gene expression. Comparative quantitative analyses of transformant populations by flow cytometry and qRT-PCR demonstrated the highest Venus expression from the EF promoter and the NR promoter if extended by an N-terminal 14-amino acid leader sequence. The kinetics of reporter gene expression were analysed during photobioreactor cultivation, achieving Venus yields of 0.3% (for EF) and 4.9% (for NR::LS) of total soluble protein. Since inducible expression systems enable the production of toxic proteins, we developed an auto-induction medium for the NR promoter transformants. By switching the N source from ammonium to nitrate in the presence of low ammonium concentrations, the starting point of Venus induction could be fine-tuned and shifted towards exponential growth phase while maintaining high recombinant protein yields. Taken together, we demonstrate that a model recombinant protein can be produced robustly and at very high levels in N. oceanica not only under constitutive but also under auto-inducible cultivation conditions. KEY POINTS: • Nannochloropsis oceanica might serve as host for recombinant protein production. • Comparative promoter strength analyses were conducted for twelve different constructs. • Robust high-yield recombinant protein production was achieved under constitutive conditions. • The nitrate reductase promoter enabled protein production under auto-induction conditions.

Project description:Margatoxin (MgTx) is a high-affinity blocker of voltage-gated potassium (Kv) channels. It inhibits Kv1.1-Kv1.3 ion channels in picomolar concentrations. This toxin is widely used to study physiological function of Kv ion channels in various cell types, including immune cells. Isolation of native MgTx in large quantities from scorpion venom is not affordable. Chemical synthesis and recombinant production in Escherichia coli need in vitro oxidative refolding for proper disulfide bond formation, resulting in a very low yield of peptide production. The Pichia pastoris expression system offers an economical approach to overcome all these limitations and gives a higher yield of correctly refolded recombinant peptides. In this study, improved heterologous expression of recombinant MgTx (rMgTx) in P. pastoris was obtained by using preferential codons, selecting the hyper-resistant clone against Zeocin, and optimizing the culturing conditions. About 36 ± 4 mg/L of >98% pure His-tagged rMgTx (TrMgTx) was produced, which is a threefold higher yield than has been previously reported. Proteolytic digestion of TrMgTx with factor Xa generated untagged rMgTx (UrMgTx). Both TrMgTx and UrMgTx blocked the Kv1.2 and Kv1.3 currents (patch-clamp) (K d for Kv1.2 were 64 and 14 pM, and for Kv1.3, 86 and 50 pM, respectively) with comparable potency to the native MgTx. The analysis of the binding kinetics showed that TrMgTx had a lower association rate than UrMgTx for both Kv1.2 and Kv1.3. The dissociation rate of both the analogues was the same for Kv1.3. However, in the case of Kv1.2, TrMgTx showed a much higher dissociation rate with full recovery of the block than UrMgTx. Moreover, in a biological functional assay, both peptides significantly downregulated the expression of early activation markers IL2R and CD40L in activated CD4+ TEM lymphocytes whose activation was Kv1.3 dependent. In conclusion, the authors report that the Pichia expression system is a powerful method to produce disulfide-rich peptides, the overexpression of which could be enhanced noticeably through optimization strategies, making it more cost-effective. Since the presence of the His-tag on rMgTx only mildly altered the block equilibrium and binding kinetics, recombinant toxins could be used in ion channel research without removing the tag and could thus reduce the cost and time demand for toxin production.

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Indirect optimization of staphylokinase expression level in dicistronic auto-inducible system.

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Indirect optimization of staphylokinase expression level in dicistronic auto-inducible system.

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