Robust preparative-scale extracellular production of hirudin in Escherichia coli and its purification and characterization

Enhanced production of recombinant proteins in Corynebacterium glutamicum using a molecular chaperone

Protein synthesis in Corynebacterium glutamicum is critical for applications in biotechnology and medicine. However, the use of C. glutamicum for protein production is limited by its low expression and aggregation. To overcome these limitations, a molecular chaperone plasmid system was developed in this study to improve the efficiency of recombinant protein synthesis in C. glutamicum. The effect of molecular chaperones on target protein synthesis (Single-chain variable fragment, Scfv) under three different promoter strengths was tested. In addition, the plasmid containing the molecular chaperone and target protein was verified for growth stability and plasmid stability. This expression model was further validated using two recombinant proteins, human interferon-beta (Hifn) and hirudin variant III (Rhv3). Finally, the Rhv3 protein was purified, and analysis of Rhv3 activity confirmed that the use of a molecular chaperone led to an improvement in test protein synthesis. Thus, the use of molecular chaperones is believed to will improve recombinant proteins synthesis in C. glutamicum.

Construction of a 3A system from BioBrick parts for expression of recombinant hirudin variants III in Corynebacterium glutamicum

Standardized parts can be efficiently assembled into novel biological systems using the three antibiotic (3A) system, ensuring the reusability of components and repeatability of experiments. In this study, we created the 3A expression system for easy construction of gene expression cassettes in Corynebacterium glutamicum (C. glutamicum), which was applied to screen combinations of promoters and signal peptides for improved secreted rhv3 production. We first obtained three strong promoters P₂₂₅₂, P_odhi, and P_yweA from all of promoters, which drive the highest expression of green fluorescent protein (egfp). The three promoters were then assembled with different signal peptides to generate a series of constructs using the 3A expression system developed in this study, from which the highest activity of rhv3 reached 3187.5 ATU/L of P_yweA-CspA-rhv3. Further increased production of rhv3 achieved large-scale fermentation using 5-L jar bioreactor, with the highest rhv3 accumulation 1.21 g/L obtained after 40 h of cultivation, which is higher than 0.95 g/L reported in E. coli. To the best of our knowledge, this is the first report of rhv3 secretory expression in C. glutamicum, which could be applied for the production of other recombinant proteins with significant applications.Key points• We have exploited a 3A system for the genetic manipulation in C. glutamicum.• We constructed element libraries for assembling standard sequence in C. glutamicum.• The secreted expression of rhv3 was realized by 3A system in C. glutamicum.

Enhanced anticoagulant activity of hirudin-i analogue co-expressed with arylsulfotransferase in periplasm of E. coli BL21(DE3)

Hirudin, a blood anticoagulant, is the most potent natural thrombin inhibitor of leech origin. Its application is limited because it is difficult to obtain abundant natural hirudin directly from the leech. Although some bioengineering methods can significantly increase the production of hirudin, the reduced efficacy of recombinant hirudin (rH) remains a critical shortcoming. The lack of sulfation of tyrosine 63 in rH is an important cause of its inadequate performance. This article is the first report of periplasmic co-expression of an rH-I analogue with arylsulfotransferase (ASST) in E. coli BL21(DE3). Co-expressed rH-I analogue with sulfate donor substrate (p-nitrophenyl sulfate potassium) showed anticoagulant (rabbit and goat serum) activity twice more than rH-I analogue expressed without ASST, indicating its potential periplasmic sulfation. Moreover, purified rH-I analogue showed above 4.5 times higher anticoagulant activity compared to therapeutic anti-thrombotic heparin (HE). At the same time, pH-dependent differential solubility was employed to purify rH analogues from fermentation broth, which is a simple, fast and inexpensive purification technology, and can potentially be used for larger scale purification. This will also greatly improve the application of rH in clinical treatment.

Transcriptomic Analysis of the Influence of Methanol Assimilation on the Gene Expression in the Recombinant Pichia pastoris Producing Hirudin Variant 3

Hirudin and its variants, as strong inhibitors against thrombin, are present in the saliva of leeches and are recognized as potent anticoagulants. However, their yield is far from the clinical requirement up to now. In this study, the production of hirudin variant 3 (HV3) was successfully realized by cultivating the recombinant Pichia pastoris GS115/pPIC9K-hv3 under the regulation of the promoter of AOX1 encoding alcohol oxidase (AOX). The antithrombin activity in the fermentation broth reached the maximum value of 5000 ATU/mL. To explore an effective strategy for improving HV3 production in the future, we investigated the influence of methanol assimilation on the general gene expression in this recombinant by transcriptomic study. The results showed that methanol was partially oxidized into CO₂, and the rest was converted into glycerone-P which subsequently entered into central carbon metabolism, energy metabolism, and amino acid biosynthesis. However, the later metabolic processes were almost all down-regulated. Therefore, we propose that the up-regulated central carbon metabolism, energy, and amino acid metabolism should be beneficial for methanol assimilation, which would accordingly improve the production of HV3.

Hirudin variants production by genetic engineered microbial factory

Hirudin was discovered as an active anticoagulant in leech extracts almost 60 years ago. Since their initial discovery, hirudin and its variants have been produced with various anti-thrombotic, cancer cell inhibition, diabetic cataract treatment and anti-fatigue activities. Some hirudin variants have been approved for clinical use and released into the marketplace. Recent progress has seen made in relation to hirudin variants expressed in several well-established microbial hosts, including Escherichia coli, Saccharomyces cerevisiae, Pichia pastoris and others, with high levels of activity and yield. This review summarizes the current progress on hirudin production using microbial producers, and considers the outlook for future development.

A novel Ffu fusion system for secretory expression of heterologous proteins in Escherichia coli

Background

The high level of excretion and rapid folding ability of β-fructofuranosidase (β-FFase) in Escherichia coli has suggested that β-FFase from Arthrobacter arilaitensis NJEM01 can be developed as a fusion partner.

Methods

Based on the modified Wilkinson and Harrison algorithm and the preliminary verification of the solubility-enhancing ability of β-FFase truncations, three β-FFase truncations (i.e., Ffu209, Ffu217, and Ffu312) with a native signal peptide were selected as novel Ffu fusion tags. Four difficult-to-express protein models; i.e., CARDS TX, VEGFR-2, RVs and Omp85 were used in the assessment of Ffu fusion tags.

Results

The expression levels and solubility of each protein were markedly enhanced by the Ffu fusion system. Each protein had a favorable Ffu tag. The Ffu fusion tags performed preferably when compared with the well-known fusion tags MBP and NusA. Strikingly, it was confirmed that Ffu fusion proteins were secreted into the periplasm by the periplasmic analysis and N-amino acid sequence analysis. Further, efficient excretion of HV3 with defined anti-thrombin activity was obtained when it was fused with the Ffu312 tag. Moreover, HV3 remained soluble and demonstrated notable anti-thrombin activity after the removal of the Ffu312 tag by enterokinase.

Conclusions

Observations from this work not only complements fusion technologies, but also develops a novel and effective secretory system to solve key issues that include inclusion bodies and degradation when expressing heterologous proteins in E. coli, especially for proteins that require disulfide bond formation, eukaryotic-secreted proteins, and membrane-associated proteins.

Electronic supplementary material

The online version of this article (10.1186/s12934-017-0845-z) contains supplementary material, which is available to authorized users.

Hirudin as a novel fusion tag for efficient production of lunasin in Escherichia coli

Fusion expression provides an effective means for the biosynthesis of longer peptides in Escherichia coli. However, the commonly used fusion tags are primarily suitable for laboratory scale applications due to the high cost of commercial affinity resins. Herein, a novel approach exploiting hirudin as a multipurpose fusion tag in combination with tobacco etch virus (TEV) protease cleavage has been developed for the efficient and cost-effective production of a 43-amino acid model peptide lunasin in E. coli at preparative scale. A fusion gene which allows for lunasin to be N-terminally fused to the C-terminus of hirudin through a flexible linker comprising a TEV protease cleavage site was designed and cloned in a secretion vector pTASH. By cultivation in a 7-L bioreactor, the fusion protein was excreted into the culture medium at a high yield of ~380 mg/L, which was conveniently recovered and purified by inexpensive HP20 hydrophobic chromatography at a recovery rate of ~80%. After polishing and cleavage with TEV protease, the finally purified lunasin was obtained with ≥95% purity and yield of ~86 mg/L culture medium. Conclusively, this hirudin tagging strategy is powerful in the production of lunasin and could be applicable for the production of other peptides at preparative scale.

Inhibitory effect of r-hirudin variant III on streptozotocin-induced diabetic cataracts in rats

The in vivo inhibitory effect of r-hirudin variant III (rHV3) on streptozotocin (STZ)-induced diabetic cataracts in rats was investigated. SD-rats were firstly made diabetic by a single intraperitoneal injection of 2% (W/V) STZ (65 mg/kg). Two weeks later, cataract formation was examined by slit lamp microscope, and the cataracted animals were randomly grouped. The animals in the treated groups received rHV3 drops administration to the eyes with various doses. After 4 weeks treatment, the animals were sacrificed to evaluate the biochemical changes of aldose reductase (AR), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and malondialdehyde (MDA) levels in the eye lens. Meanwhile, the cataract progression was monitored by slit lamp microscope. As a result, rHV3 drops treatment significantly increased the activities of SOD and GSH-Px in the lens in a dose-dependent manner, whereas AR activity and MDA level in the lens were dramatically decreased. Also, the morphological observation further confirmed the inhibition of the development of STZ-induced diabetic cataracts by the rHV3 drops treatment. Thus, our data suggest that rHV3 drops are pharmacologically effective for the protection against STZ-induced diabetic cataracts in rats.