Recombinant protein production data after expression in the bacterium Escherichia coli

Engineered small metal-binding protein tag improves the production of recombinant human growth hormone in the periplasm of Escherichia coli

Fusion proteins play an important role in the production of recombinant proteins in Escherichia coli. They are mostly used for cytoplasmic expression since they can be designed to increase the solubility of the target protein, which then can be easily purified via affinity chromatography. In contrast, fusion proteins are not usually included in construct designs for periplasmic production. Instead, a signal sequence is inserted for protein transport into the periplasm and a C-terminal his-tag added for subsequent purification. Our research group has proposed the small metal-binding protein (SmbP) isolated from the periplasm of Nitrosomonas europaea as a new fusion protein to express recombinant proteins in the cytoplasm or periplasm of E. coli. SmbP also allows purification via immobilized metal affinity chromatography using Ni(II) ions. Recently, we have optimized the periplasmic production of proteins tagged with SmbP by exchanging its native signal peptide with one taken from pectate lyase B (PelB), substantially increasing the amount of protein produced. In this work, we have expressed and purified soluble bioactive human growth hormone (hGH) tagged with PelB-SmbP and obtained the highest periplasmic production reported for this protein so far. Its activity, tested on Nb2-11 cells, was equivalent to commercial growth hormone at 50 ng·mL-1 . Therefore, we strongly recommend the use of PelB-SmbP as a protein tag for the expression and purification of hGH or other possible target proteins in the periplasm of E. coli.

Optimizing Periplasmic Expression in Escherichia coli for the Production of Recombinant Proteins Tagged with the Small Metal-Binding Protein SmbP

We have previously shown that the small metal-binding protein (SmbP) extracted from the gram-negative bacterium Nitrosomonas europaea can be employed as a fusion protein for the expression and purification of recombinant proteins in Escherichia coli. With the goal of increasing the amounts of SmbP-tagged proteins produced in the E. coli periplasm, we replaced the native SmbP signal peptide with three different signal sequences: two were from the proteins CusF and PelB, for transport via the Sec pathway, and one was the signal peptide from TorA, for transport via the Tat pathway. Expression of SmbP-tagged Red Fluorescent Protein (RFP) using these three alternative signal peptides individually showed a considerable increase in protein levels in the periplasm of E. coli as compared to its level using the SmbP signal sequence. Therefore, for routine periplasmic expression and purification of recombinant proteins in E. coli, we highly recommend the use of the fusion proteins PelB-SmbP or CusF-SmbP, since these signal sequences increase periplasmic production considerably as compared to the wild-type. Our work, finally, demonstrates that periplasmic expression for SmbP-tagged proteins is not limited to the Sec pathway, in that the TorA-SmbP construct can export reasonable quantities of folded proteins to the periplasm. Although the Sec route has been the most widely used, sometimes, depending on the nature of the protein of interest, for example, if it contains cofactors, it is more appropriate to consider using the Tat route over the Sec. SmbP therefore can be recommended in terms of its particular versatility when combined with signal peptides for the two different routes.

Biochemical and in silico evaluation of recombinant E. coli aminopeptidase and in vitro processed human interferon α-2b

Escherichia coli is an extensively used host for the production of recombinant proteins, making its N-terminal methionine aminopeptidase (MAP) an attractive candidate for studies on posttranslational protein processing. The present study describes the recombinant production and properties of MAP from the DH5α strain of E. coli. The soluble and active enzyme was produced in E. coli BL21 (DE3) RIL - codon plus cells under a T7 promoter system and purified by anion-exchange chromatography. It exhibited a molecular weight of 29,200.94 Da by MALDI-TOF analysis. The purified enzyme showed specific activity of 1.64 U/mg with methionylp-nitroanilide and 1.51 U/mg with synthetic tetrapeptide substrate 'MGMM' in a discontinuous HPLC-based assay. In vitro studies showed the processing of up to 36% of Met-INFα-2b in 40 min. In silico studies revealed that the ES-complex formation between the enzyme and interferon has a ΔG -683.07 kJ/mol. Molecular docking results showed that the processed INFα-2b has greater binding affinity with IFNAR2 receptor as indicated by ΔG -784.53 kJ/mol, significantly lower than that of methionine containing INFα-2b (ΔG -717.63 kJ/mol). These findings emphasize the functional superiority or better efficacy of N-terminal methionine processed recombinant interferon.

Efficient and easily scalable protein folding strong anion exchange chromatography for renaturation and simultaneous purification of recombinant human asparaginase from E. coli

Recombinant proteins are revolutionizing present day therapeutics. They are generally expressed as insoluble inclusion bodies in the E. coli and mis-folding, loss of protein, and high cost of down streaming are the hurdles in their recovery. For the first time, we are reporting the refolding with simultaneous purification of rhASP in E. coli using a single step utilizing protein folding-strong anion exchange chromatography (PF-SAX). The purification method is also standardized for optimal concentration of solution additives, pH, and mobile phase composition. The results showed purification of rhASP with anion exchange chromatography was effective. Phosphate buffer and slightly alkaline pH produced significant recovery yields and purity profiles. The effect of solution additives such as arginine, glycerol, TMAO, sorbitol, dextran, glutamate, and fructose on rhASP renaturation is also investigated. Significant results were achieved using arginine-TMAO combination in terms of purity, recovery yield and specific activity of 99%, 78%, and 210 IU/mg, respectively. The work concludes that PF-SAX refolding method is superior to other conventional methods and it can be applied to large scale purification of rhASP produced in E. coli. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:1036-1044, 2018.