Thioredoxin fusion construct enables high-yield production of soluble, active matrix metalloproteinase-8 (MMP-8) in Escherichia coli

Development and Evaluation of an Immunoinformatics-Based Multi-Peptide Vaccine against Acinetobacter baumannii Infection

Multi-drug-resistant (MDR) Acinetobacter baumannii is an opportunistic pathogen associated with hospital-acquired infections. Due to its environmental persistence, virulence, and limited treatment options, this organism causes both increased patient mortality and incurred healthcare costs. Thus, prophylactic vaccination could be ideal for intervention against MDR Acinetobacter infection in susceptible populations. In this study, we employed immunoinformatics to identify peptides containing both putative B- and T-cell epitopes from proteins associated with A. baumannii pathogenesis. A novel Acinetobacter Multi-Epitope Vaccine (AMEV2) was constructed using an A. baumannii thioredoxin A (TrxA) leading protein sequence followed by five identified peptide antigens. Antisera from A. baumannii infected mice demonstrated reactivity to rAMEV2, and subcutaneous immunization of mice with rAMEV2 produced high antibody titer against the construct as well as peptide components. Immunization results in increased frequency of IL-4-secreting splenocytes indicative of a Th2 response. AMEV2-immunized mice were protected against intranasal challenge with a hypervirulent strain of A. baumannii and demonstrated reduced bacterial burden at 48 h. In contrast, all mock vaccinated mice succumbed to infection within 3 days. Results presented here provide insight into the effectiveness of immunoinformatic-based vaccine design and its potential as an effective strategy to combat the rise of MDR pathogens.

Apolipoprotein E4 heterologous expression, purification under non-denaturing conditions, and effects on neuronal clonal cell lines

The ε4 allele of the apolipoprotein E gene (APOE4) constitutes the main genetic risk factor for late-onset Alzheimer disease (AD). High amounts of pure apolipoprotein E4 (ApoE4), in a rapid and reproducible fashion, could be of value for studying its pathophysiological roles in AD. The aim of the present work was to optimize a preparative method to obtain highly purified recombinant ApoE4 (rApoE4) with full biological activity. rApoE4 was expressed in the E. Coli BL21(D3) strain and a soluble form of the protein was purified by a combination of affinity and size-exclusion chromatography that precluded a denaturation step. The structural integrity and the biochemical activity of the purified rApoE4 were confirmed by circular dichroism and a lipid-binding assay. Several biological parameters affected by rApoE4, such as mitochondrial morphology, mitochondrial membrane potential and reactive oxygen species production were studied in CNh cells, a neuronal cell line, and neurodifferentiation and dendritogenesis were analyzed in the SH-SY5Y neuroblastoma cell line. The improved rApoE4 purification technique reported here enables the production of highly purified protein that retain the structural properties and functional activity of the native protein, as confirmed by tests in two different neuronal cell lines in culture.

An undefined cystatin CsCPI1 from tea plant Camellia sinensis harbors antithrombotic activity

Tea consumption has been linked to a decreased risk of cardiovascular disease (CVD) mortality, which imposes a heavy burden on the healthcare system; however, which components in tea cause this beneficial effect is not fully understood. Here we uncovered a cystatin (namely CsCPI1), which is a cysteine proteinase inhibitor (CPI) of the tea plant (Camellia sinensis) that promotes antithrombotic activity. Since thrombosis is a common pathogenesis of fatal CVDs, we investigated the effects of CsCPI1, which showed good therapeutic effects in mouse models of thrombotic disease and ischemic stroke. CsCPI1 significantly increases endothelial cell production of nitric oxide (NO) and inhibits platelet aggregation. Notably, CsCPI1 exhibited no cytotoxicity or resistance to pH and temperature changes, which indicates that CsCPI1 might be a potent antithrombotic agent that contributes to the therapeutic effects of tea consumption against CVD. Specifically, the antithrombotic effects of CsCPI1 are distinct from the classical function of plant cystatins against herbivorous insects. Therefore, our study proposes a new potential role of cystatins in CVD prevention and treatment, which requires further study.

Systems and strategies for plant protein expression

At least a quarter of the protein-encoding genes in plant genomes are predicted to encode enzymes for which no physiological function is known. Determining functions for these uncharacterized enzymes is key to understanding plant metabolism. Functional characterization typically requires expression and purification of recombinant enzymes to be used in enzyme assays and/or for protein structure elucidation studies. Here, we describe several practical considerations used to improve the heterologous expression and purification of Arabidopsis thaliana and Zea mays NAD(P)HX dehydratase (NAXD) and NAD(P)HX epimerase (NAXE), two enzymes that are involved in repair of chemically damaged NAD(P)H cofactors. We provide protocols for transit peptide prediction and construct design, expression in Escherichia coli, and purification of NAXD and NAXE. Many of these strategies are generally applicable to the purification of any plant protein.

SHTXTHHly, an extracellular secretion platform for the preparation of bioactive peptides and proteins in Escherichia coli

BACKGROUND

In previous work, we developed an E. coli extracellular secretion platform XTHHly based on the hemolysin A secretion system. It can produce bioactive peptides with simple purification procedures. However, the wider application of this platform is limited by poor secretion efficiency.

RESULTS

In this study, we first discovered a positive correlation between the isoelectric point (pI) value of the target protein and the secretion level of the XTHHly system. Given the extremely high secretion level of S tag, we fused it at the N-terminus and created a novel SHTXTHHly system. The SHTXTHHly system significantly increased the secretion levels of antimicrobial peptides (PEW300, LL37, and Aurein 1.2) with full bioactivities, suggesting its excellent capacity for secretory production of bioactive peptides. Furthermore, RGDS, IL-15, and alcohol dehydrogenase were successfully secreted, and their bioactivities were largely maintained in the fusion proteins, indicating the potential applications of the novel system for the rapid determination of protein bioactivities. Finally, using the SHTXTHHly system, we produced the monomeric Fc, which showed a high affinity for Fcγ Receptor I and mediated the antibody-dependent immunological effects of immune cells, demonstrating its potential applications in immunotherapies.

CONCLUSIONS

The SHTXTHHly system described here facilitates the secretory production of various types of proteins in E. coli. In comparison to previously reported expression systems, our work enlightens an efficient and cost-effective way to evaluate the bioactivities of target proteins or produce them.

Synthetic fish metallothionein design as a potential tool for monitoring toxic metals in water

The diversity of aquatic ecosystems impacted by toxic metals is widely distributed throughout the world. The application of metallothionein (MT) as an early warning sign of metal exposure in freshwater fish is important in biomonitoring, but a more accessible, sensitive, safe, and efficient new methodological strategy is necessary. On this way, a fish MT synthetic gene from Oreochromis aureos was expressed in Escherichia coli to produce polyclonal antibodies against the protein. In the validation assays, these antibodies were able to detect hepatic MT from freshwater fishes Oreochromis niloticus, Pimelodus maculatus, Prochilodus lineatus, and Salminus brasiliensis showing a potential tool for toxic metals biomarker in biomonitoring of aquatic ecosystems. The current results showed the applicability of this molecule in quantitative immunoassays as a sensor for monitoring aquatic environments impacted by toxic metals. Due to the lack of methods focusing on metal pollution diagnostics in aquatic ecosystems, the current proposal revealed a promising tool to applications in biomonitoring programs of water resources, mainly in Brazil where the mining activity is very developed.

Recombinant Expression and Stapling of a Novel Long-Acting GLP-1R Peptide Agonist

Owing to their pleiotropic metabolic benefits, glucagon-like peptide-1 receptor (GLP-1R) agonists have been successfully utilized for treating metabolic diseases, such as type 2 diabetes and obesity. As part of our efforts in developing long-acting peptide therapeutics, we have previously reported a peptide engineering strategy that combines peptide side chain stapling with covalent integration of a serum protein-binding motif in a single step. Herein, we have used this strategy to develop a second generation extendin-4 analog rigidified with a symmetrical staple, which exhibits an excellent in vivo efficacy in an animal model of diabetes and obesity. To simplify the scale-up manufacturing of the lead GLP-1R agonist, a semisynthesis protocol was successfully developed, which involves recombinant expression of the linear peptide followed by attachment of a polyethylene glycol (PEG)-fatty acid staple in a subsequent chemical reaction step.

Selection of High Producers From Combinatorial Libraries for the Production of Recombinant Proteins in Escherichia coli and Vibrio natriegens

The optimization of recombinant protein production in bacteria is an important stage of process development, especially for difficult-to-express proteins that are particularly sensitive or recalcitrant. The optimal expression level must be neither too low, which would limit yields, nor too high, which would promote the formation of insoluble inclusion bodies. Expression can be optimized by testing different combinations of elements such as ribosome binding sites and N-terminal affinity tags, but the rate of protein synthesis is strongly dependent on mRNA secondary structures so the combined effects of these elements must be taken into account. This substantially increases the complexity of high-throughput expression screening. To address this limitation, we generated libraries of constructs systematically combining different ribosome binding sites, N-terminal affinity tags, and periplasmic translocation sequences representing two secretion pathways. Each construct also contained a green fluorescent protein (GFP) tag to allow the identification of high producers and a thrombin cleavage site enabling the removal of fusion tags. To achieve proof of principle, we generated libraries of 200 different combinations of elements for the expression of an antimicrobial peptide (AMPs), an antifungal peptide, and the enzyme urate oxidase (uricase) in Escherichia coli and Vibrio natriegens. High producers for all three difficult-to-express products were enriched by fluorescence-activated cell sorting. Our results indicated that the E. coli ssYahJ secretion signal is recognized in V. natriegens and efficiently mediates translocation to the periplasm. Our combinatorial library approach therefore allows the cross-species direct selection of high-producer clones for difficult-to-express proteins by systematically evaluating the combined impact of multiple construct elements.

Cloning and characteristic of MMP1 gene from Hyriopsis cumingii and collagen hydrolytic activity of its recombinant protein

Matrix metalloproteinases (MMPs) play an essential role in a variety of biological processes including wound healing, inflammation, cell invasion, angiogenesis and immune defense. In this study, a putative MMP1 cDNA was cloned and characterized from Hyriopsis cumingii (designated as HcMMP1). The cDNA was 1822 bp in length and encoded a putative protein of 510 amino acids, with a predicted molecular mass of 58.28 kDa and an isoelectric point (pI) of 9.27. HcMMP1 contained all prototype MMPs family signatures, such as signal peptide, prodomain, catalytic center, hinge region, and hemopexin like domain. Quantitative real time-PCR (qRT-PCR) revealed that in mussels HcMMP1 mRNA was expressed in all tissues tested, and the transcriptional expression levels were significantly up-regulated in hepatopancreas and hemocytes after Aeromonas hydrophila, peptidoglycan stimulations and in mantle after wounding. Moreover, the recombination HcMMP1 protein, successfully expressed in Escherichia coli, was purified by affinity chromatography with the concentration of final yield at 0.3 mg/mL. The recombinase had an essentially hydrolytic activity toward rat type I collagen, mouse II and IV collagen after renaturation.

The 3D protein of duck hepatitis A virus type 1 binds to a viral genomic 3' UTR and shows RNA-dependent RNA polymerase activity

To explore the RNA-dependent RNA polymerase (RdRP) function of the 3D protein of duck hepatitis A virus type 1 (DHAV-1), the gene was cloned into the pET-32a(+) vector for prokaryotic expression. The 3' untranslated region (3' UTR) of DHAV-1 together with a T7 promoter was cloned into the pMD19-T vector for in vitro transcription of 3' UTR RNA, which was further used as a template in RNA-dependent RNA polymerization. In this study, three methods were applied to analyze the RdRP function of the 3D protein: (1) ammonium molybdate spectrophotometry to detect pyrophosphate produced during polymerization; (2) quantitative reverse transcription PCR (RT-qPCR) to investigate the changes in RNA quantity during polymerization; and (3) electrophoresis mobility shift assay to examine the interaction between the 3D protein and 3' UTR. The results showed the 3D protein was successfully expressed in bacteria culture supernatant in a soluble form, which could be purified by affinity chromatography. In 3D enzymatic activity assays, pyrophosphate and RNA were produced, the amounts of which increased based on approximative kinetics, and binding of the 3D protein to the 3' UTR was observed. These results indicate that prokaryotically expressed soluble DHAV-13D protein can bind to a viral genomic 3' UTR and exhibit RdRP activity.

Mechanistic investigations of matrix metalloproteinase-8 inhibition by metal abstraction peptide

The mechanism of matrix metalloproteinase-8 (MMP-8) inhibition was investigated using ellipsometric measurements of the interaction of MMP-8 with a surface bound peptide inhibitor, tether-metal abstraction peptide (MAP), bound to self-assembled monolayer films. MMP-8 is a collagenase whose activity and dysregulation have been implicated in a number of disease states, including cancer metastasis, diabetic neuropathy, and degradation of biomedical reconstructions, including dental restorations. Regulation of activity of MMP-8 and other matrix metalloproteinases is thus a significant, but challenging, therapeutic target. Strong inhibition of MMP-8 activity has recently been achieved via the small metal binding peptide tether-MAP. Here, the authors elucidate the mechanism of this inhibition and demonstrate that it occurs through the direct interaction of the MAP Tag and the Zn(2+) binding site in the MMP-8 active site. This enhanced understanding of the mechanism of inhibition will allow the design of more potent inhibitors as well as assays important for monitoring critical MMP levels in disease states.