An improved strategy of TGFβ3 expression in Escherichia coli: Exploiting folding modulators for a switch from misfolded to folded form

Escherichia coli as a versatile cell factory: Advances and challenges in recombinant protein production

E. coli plays a substantial role in recombinant protein production. Its importance increased with the discovery of recombinant DNA technology and the subsequent production of the first recombinant insulin in E. coli. E. coli is a widely used and cost-effective host to produce recombinant proteins. It is also noteworthy that a significant portion of the approved therapeutic proteins have been produced in this organism. Despite these advantages, it has some disadvantages, such as toxicity and lack of eukaryotic post-translational modifications that can lead to the production of misfolded, insoluble, or dysfunctional proteins. This study focused on the challenges and engineering approaches for improved expression and solubility in recombinant protein production in E. coli. In this context, solution strategies such as strain and vector selection, codon usage, mRNA stability, expression conditions, translocation to the periplasmic region and addition of fusion tags in E. coli were discussed.

Promoting soluble expression of hybrid mussel foot proteins by SUMO-TrxA tags for production of mussel glue

Mussel foot proteins (Mfps) display application potential with strong adhesion, enabling mussels to adhere firmly to various surfaces. Mytilus galloprovincialis foot protein 3B (Mgfp-3B) exhibits this characteristic remarkably. However, it remains a challenge for further research due to the low soluble expression of heterologous production. In this study, a small ubiquitin-related modifier (SUMO) and thioredoxin A (TrxA), which catalyzed the proper folding of disulfide bridges, were selected to increase the soluble expression of mfps. An additional ribosome binding site was introduced between the molecular chaperones and Mgfp-3B (fp-3) to form a bicistronic translation-coupled expression vector for co-expression. The results revealed that the combination of SUMO-TrxA increased the soluble expression of fp-3 by 18.07 %. Furthermore, the SUMO-TrxA also boosted the soluble expression of hybrid mfps Mgfp-3B-Mfp-1 (fp-3-1) by 11.29 %, Mgfp-3B-Mgfp-3B (fp-3-3) by 19.91 %, and Mgfp-3B-Mgfp-5 (fp-3-5) by 14.03 %. Ultimately, by high cell density cultivation in a 5 L bioreactor, the yields of fp-3, fp-3-3, and fp-3-5 co-expressed with SUMO-TrxA reached 217.75 mg/L, 127.2 mg/L, and 97.28 mg/L, respectively. Consequently, soluble production of mfps holds great potential for the sustainable supply of protein adhesive materials.

Role of molecular and chemical chaperon in assisting refolding of BMP2 in E. coli

Bone morphogenetic protein 2 (BMP2) when expressed in bacteria forms inclusion bodies (IBs) due to its complex disulfide-rich structure. Chaperons are already well known for their role in assisting protein folding. In our studies, we have used two E. coli strains, BL21(DE3) and SHuffle® T7 cells for overexpressing BMP2 in soluble fraction. We observed that SHuffle® T7 cells successfully expressed soluble functionally active BMP2 in presence of molecular and chemical chaperones at low temperature. The combination of chemical and molecular chaperons further increases the yield of protein. The best-suited chaperon system for overexpression of BMP2 is GroES-GroEL at low temperature. The soluble functionally active BMP2 is confirmed by its binding to its receptor ALK3 through Native PAGE and ELISA assay using BMP2 specific antibody. It is possible to obtain BMP2 expression in soluble active form by using molecular and chemical chaperons which work synergistically in bacterial cells to fold disulphide-rich proteins at low temperature in easy and time saving steps (18 ̊C).

Soluble Diphtheria Toxin Variant, CRM 197 was Obtained in Escherichia coli at High Productivity Using SUMO Fusion and an Adjusted Expression Strategy

Background:

CRM197, a non-toxic diphtheria toxin variant, is widely used as a polysaccharide carrier in a variety of conjugate vaccines and also exhibits antitumor activity. CRM197 commercial production is limited due to the low yield of Corynebacterium diphtheriae C7 (197) tox-. Developing an efficient method for recombinant CRM197 production reduces production costs and is critical for expanding the application coverage of related medical products and basic research. Escherichia coli is a frequently used host for heterologous protein synthesis. However, the primary limitation of this system is the inclusion body formation and the low yield of active protein recovery.

Objective:

As a result, we attempted to produce CRM197 in the soluble form in E. coli using a small ubiquitin-related modifier (SUMO) tag fusion and an expression strategy optimized for protein production.

Methods:

CRM197 was expressed intracellularly in E. coli BL21 (DE3) with its N-terminus fused to a SUMO tag preceded by a histidine tag (HSCRM197). To improve the solubility of HSCRM197 in E. coli, a response surface method (RSM) experimental design was used based on three factors: expression temperature, inducer concentration, and sorbitol inclusion in the culture medium. Metal affinity chromatography was used to purify HSCRM197, and the SUMO tag was removed using the SUMO protease's catalytic domain. After adsorbing the SUMO tag on a Ni-NTA column, CRM197 was obtained. DNA degradation activity was determined for both HSCRM197 and CRM197.

Results:

When HSCRM197 was expressed in E. coli under common expression conditions (37ºC, 1000 μM inducer), 15.4% of the protein was found in the cellular soluble fraction. However, when the RSM-derived expression conditions were used (30ºC, 510 μM inducer, and 200 mM sorbitol), the obtained HSCRM197 was almost completely soluble (96.5% solubility), and the system productivity was 32.67 μg ml-1 h-1. HSCRM197 and CRM197 both exhibited nuclease activity. However, the activity of CRM197 was greater than that of HSCRM197.

Conclusion:

These findings established the utility of the method developed in this study to produce CRM197 for medical applications.

Nanobody as solubilization chaperone for the expression and purification of inclusion-body prone proteins

Here we report a new protocol for enhancing the soluble expression of inclusion body (IB)-prone proteins in E. coli using nanobody (Nb) as a molecular-specific chaperone. The specific intracellular binding...