Enhanced prokaryotic expression, purification, and biological activities of human keratinocyte growth factor

Keratinocyte growth factor (KGF), also known as fibroblast growth factor 7 (FGF7), plays a critical role in embryonic development, cell proliferation, and differentiation. However, efficient production of recombinant KGF remains a challenge due to its low expression levels and high tendency for aggregation in Escherichia coli. This study aimed to enhance the expression and solubility of KGF by employing different protein tags-PDIb'a', MBP, and His-fused to the N-terminus of KGF. Among these, H-PDIb'a'-KGF demonstrated superior stability and was selected for large-scale production and purification. The purified KGF was confirmed through liquid chromatography with tandem mass spectrometry analysis, which showed an 81% fragment mass identification coverage. Biological activity assessments using human breast cancer MCF-7 cells indicated that purified KGF significantly increased cell proliferation, with an EC50 of 6.4 ± 0.5 pM. Interestingly, PDIb'a' alone also exhibited a stimulatory effect on MCF-7 cells. Furthermore, the purified KGF enhanced the wound healing of HaCaT keratinocytes in a dose-dependent manner. These findings provide valuable insights into the efficient production and functional characterization of recombinant KGF for potential applications in therapeutic interventions.

AviTrap: A novel solution to achieve complete biotinylation

Site specific biotinylation of AviTagged recombinant proteins using BirA enzyme is a widely used protein labeling technology. However, due to the incomplete biotinylation reactions and the lack of a purification method specific for the biotinylated proteins, it is challenging to purify the biotinylated sample when mixed with the non-biotinylated byproduct. Here, we have developed a monoclonal antibody that specifically recognizes the non-biotinylated AviTag but not the biotinylated sequence. After a ten-minute incubation with the resin that is conjugated with the antibody, the non-biotinylated AviTagged protein is trapped on the resin while the fully biotinylated material freely passes through. Therefore, our AviTrap (anti-AviTag antibody conjugated resin) provides an efficient solution for enriching biotinylated AviTagged proteins via a simple one-step purification.

Homologous Overexpression of Tyrosinase in Trichoderma reesei and Its Application in Glycinin Cross-Linking

Tyrosinase is capable of oxidizing tyrosine residues in proteins, leading to intermolecular protein cross-linking, which could modify the protein network of food and improve the texture of food. To obtain the recombinant tyrosinase with microbial cell factory instead of isolation tyrosinase from the mushroom Agaricus bisporus, a TYR expression cassette was constructed in this study. The expression cassette was electroporated into Trichoderma reesei Rut-C30 and integrated into its genome, resulting in a recombinant strain C30-TYR. After induction with microcrystalline cellulose for 7 days, recombinant tyrosinase could be successfully expressed and secreted by C30-TYR, corresponding to approximately 2.16 g/L tyrosinase in shake-flask cultures. The recombinant TYR was purified by ammonium sulfate precipitation and gel filtration, and the biological activity of purified TYR was 45.6 U/mL. The purified TYR could catalyze the cross-linking of glycinin, and the emulsion stability index of TYR-treated glycinin emulsion was increased by 30.6% compared with the untreated one. The cross-linking of soy glycinin by TYR resulted in altered properties of oil-in-water emulsions compared to emulsions stabilized by native glycinin. Therefore, cross-linking with this recombinant tyrosinase is a feasible approach to improve the properties of protein-stabilized emulsions and gels.

Expression, Purification, and Biological Evaluation of XTEN-GCSF in a Neutropenic Rat Model

Granulocyte colony-stimulating factor (GCSF) stimulates the proliferation of neutrophils but it has low serum half-life. Therefore, the present study was done to investigate the effect of XTENylation on biological activity, pharmacokinetics, and pharmacodynamics of GCSF in a neutropenic rat model. XTEN tag was genetically fused to the N-terminal region of GCSF-encoding gene fragment and subcloned into pET28a expression vector. The cytoplasmic expressed recombinant protein was characterized through intrinsic fluorescence spectroscopy (IFS), dynamic light scattering (DLS), and size exclusion chromatography (SEC). In vitro biological activity of the XTEN-GCSF protein was evaluated on NFS60 cell line. Hematopoietic properties and pharmacokinetics were also investigated in a neutropenic rat model. An approximately 140 kDa recombinant protein was detected on SDS-PAGE. Dynamic light scattering and size exclusion chromatography confirmed the increase in hydrodynamic diameter of GCSF molecule after XTENylation. GCSF derivatives showed efficacy in proliferation of NFS60 cell line among which the XTEN-GCSF represented the lowest EC50 value (100.6 pg/ml). Pharmacokinetic studies on neutropenic rats revealed that XTEN polymer could significantly increase protein serum half-life in comparison with the commercially available GCSF molecules. PEGylated and XTENylated GCSF proteins were more effective in stimulation of neutrophils compared to the GCSF molecule alone. XTENylation of GCSF represented promising results in in vitro and in vivo studies. This approach can be a potential alternative to PEGylation strategies for increasing serum half-life of protein.

Expression and purification of fluorinated proteins from mammalian suspension culture

The site-specific encoding of noncanonical amino acids allows for the introduction of rationalized chemistry into a target protein. Of the methods that enable this technology, evolved tRNA and synthetase pairs offer the potential for expanded protein production and purification. Such an approach combines the versatility of solid-phase peptide synthesis with the scalable features of recombinant protein production. We describe the large scale production and purification of eukaryotic proteins bearing fluorinated phenylalanine in mammalian suspension cell preparations. Downstream applications of this approach include scalable recombinant protein preparation for ligand binding assays with small molecules and ligands, protein structure determination, and protein stability assays.

Isolation and Characterization of Monomeric Human RAD51: A Novel Tool for Investigating Homologous Recombination in Cancer

DNA repair protein RAD51 is a key player in the homologous recombination pathway. Upon DNA damage, RAD51 is transported into the nucleus by BRCA2, where it can repair DNA double-strand breaks. Due to the structural complexity and dynamics, researchers have not yet clarified the mechanistic details of every step of RAD51 recruitment and DNA repair. RAD51 possesses an intrinsic tendency to form oligomeric structures, which make it challenging to conduct biochemical and biophysical investigations. Here, for the first time, we report on the isolation and characterization of a human monomeric RAD51 recombinant form, obtained through a double mutation, which preserves the protein's integrity and functionality. We investigated different buffers to identify the most suitable condition needed to definitively stabilize the monomer. The monomer of human RAD51 provides the community with a unique biological tool for investigating RAD51-mediated homologous recombination, and paves the way for more reliable structural, mechanistic, and drug discovery studies.

Activation of the toll-like receptor 2 signaling pathway by GAPDH from bacterial strain RD055328

We characterized the membrane vesicle fraction (RD-MV fraction) from bacterial strain RD055328, which is related to members of the genus Companilactobacillus and Lactiplantibacillus plantarum. RD-MVs and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) were detected in the RD-MV fraction. Immunoglobulin A (IgA) was produced by Peyer's patch cells following the addition of the RD-MV fraction. In the presence of the RD-MV fraction, RAW264 cells produced the pro-inflammatory cytokine IL-6. Recombinant GAPDH probably induced the production of IL-6 by RAW264 cells via superficial toll-like receptor 2 (TLR2) recognition. A confocal laser scanning microscopy image analysis indicated that RD-MVs and GAPDH were taken up by RAW264 cells. GAPDH wrapped around RAW264 cells. We suggest that GAPDH from strain RD055328 enhanced the production of IgA by acquired immune cells via the production of IL-6 by innate immune cells through TLR2 signal transduction.

Protein engineering of a nanoCLAMP antibody mimetic scaffold as a platform for producing bioprocess-compatible affinity capture ligands

Protein A affinity chromatography is widely used for the large-scale purification of antibodies because of its high yield, selectivity, and compatibility with NaOH sanitation. A general platform to produce robust affinity capture ligands for proteins beyond antibodies would improve bioprocessing efficiency. We previously developed nanoCLAMPs (nano Clostridial Antibody Mimetic Proteins), a class of antibody mimetic proteins useful as lab-scale affinity capture reagents. This work describes a protein engineering campaign to develop a more robust nanoCLAMP scaffold compatible with harsh bioprocessing conditions. The campaign generated an improved scaffold with dramatically improved resistance to heat, proteases, and NaOH. To isolate additional nanoCLAMPs based on this scaffold, we constructed a randomized library of 1 × 1010 clones and isolated binders to several targets. We then performed an in-depth characterization of nanoCLAMPs recognizing yeast SUMO, a fusion partner used for the purification of recombinant proteins. These second-generation nanoCLAMPs typically had a Kd of <80 nM, a Tm of >70 °C, and a t1/2 in 0.1 mg/ml trypsin of >20 h. Affinity chromatography resins bearing these next-generation nanoCLAMPs enabled single-step purifications of SUMO fusions. Bound target proteins could be eluted at neutral or acidic pH. These affinity resins maintained binding capacity and selectivity over 20 purification cycles, each including 10 min of cleaning-in-place with 0.1 M NaOH, and remained functional after exposure to 100% DMF and autoclaving. The improved nanoCLAMP scaffold will enable the development of robust, high-performance affinity chromatography resins against a wide range of protein targets.

Quantitative assessment of LPS-HBsAg interaction by introducing a novel application of immunoaffinity chromatography

Lipopolysaccharide (LPS), as a stubborn contamination, should be monitored and kept in an acceptable level during the pharmaceutical production process. Recombinant hepatitis B surface antigen (r-HBsAg) is one of the recombinant biological products, which is probable to suffer from extrinsic endotoxin due to its long and complex production process. This research aims to assess the potential interaction between LPS and r-HBsAg by recruiting immunoaffinity chromatography (IAC) as a novel tool to quantify the interaction. Molecular modeling was performed on the HBsAg molecule to theoretically predict its potential binding and interaction sites. Then dynamic light scattering (DLS) analysis was implemented on HBsAg, LPS, and mixtures of them to reveal the interaction. The virus-like particle (VLP) structure of HBsAg and the ribbon-like structure of LPS were visualized by transmission electron microscopy (TEM). Finally, the interaction was quantified by applying various LPS/HBsAg ratios ranging from 1.67 to 120 EU/dose in the IAC. Consequently, the LPS/HBsAg ratios in the eluate were measured from 1.67 to a maximum of 92.5 EU/dose. The results indicated that 77 to 100% of total LPS interacted with HBsAg by an inverse relationship to the incubated LPS concentration. The findings implied that the introduced procedure is remarkably practical in the quantification of LPS interaction with a target recombinant protein.

Peptidoglycan recognition protein-S1 (PGRP-S1) from Diaphania pyloalis (Walker) is involved in the agglutination and prophenoloxidase activation pathway

Recognition of invading foreign exogenous pathogen is the first step to initiate the innate immune response of insects, which accomplished by the pattern recognition receptors (PRRs). Peptidoglycan recognition proteins (PGRPs) serve as an important type of PRRs, which activate immune response by detecting peptidoglycan of microbial cell wall. In this study, we have cloned the full-length cDNA of PGRP gene called PGRP-S1 from the Diaphania pyloalis (Walker). The open reading frame (ORF) of D. pyloalis PGRP-S1 encodes 211 amino acids which containing a secretion signal peptide and a canonical PGRP domain. Multisequence alignment revealed that PGRP-S1 possess the amino acid residues responsible for zinc binding and amidase activity. D. pyloalis PGRP-S1 exhibited the highest transcript level in fat body and followed in head. The mRNA concentration dramatically increased after an injection of Escherichia coli or Micrococcus luteus. Purified recombinant PGRP-S1 exhibit binding ability to peptidoglycans from Staphylococcus aureus or Bacillus subtilis and cause intensive agglutination of E. coli, M. luteus or S. aureus in the presence of zinc ions. Furthermore, phenoloxidase activity significantly increased when the plasma from larvae was incubated with recombinant PGPR-S1 and peptidoglycans from B. subtilis or M. luteus simultaneously. These results implied that PGRP-S1 was a member involving the prophenoloxidase activation pathway. Overall, our results indicated that D. pyloalis PGRP-S1 serve as a PRR to participate in the recognition of foreign pathogen and prophenoloxidase pathway stimulation.

Discovery of a Covalent FEM1B Recruiter for Targeted Protein Degradation Applications

Proteolysis-targeting chimeras (PROTACs), heterobifunctional compounds that consist of protein-targeting ligands linked to an E3 ligase recruiter, have arisen as a powerful therapeutic modality for targeted protein degradation (TPD). Despite the popularity of TPD approaches in drug discovery, only a small number of E3 ligase recruiters are available for the >600 E3 ligases that exist in human cells. Here, we have discovered a cysteine-reactive covalent ligand, EN106, that targets FEM1B, an E3 ligase recently discovered as the critical component of the cellular response to reductive stress. By targeting C186 in FEM1B, EN106 disrupts recognition of the key reductive stress substrate of FEM1B, FNIP1. We further establish that EN106 can be used as a covalent recruiter for FEM1B in TPD applications by demonstrating that a PROTAC linking EN106 to the BET bromodomain inhibitor JQ1 or the kinase inhibitor dasatinib leads to the degradation of BRD4 and BCR-ABL, respectively. Our study showcases a covalent ligand that targets a natural E3 ligase-substrate binding site and highlights the utility of covalent ligand screening in expanding the arsenal of E3 ligase recruiters suitable for TPD applications.

High-Efficiency Expression and Purification of DNAJB6b Based on the pH-Modulation of Solubility and Denaturant-Modulation of Size

The chaperone DNAJB6b delays amyloid formation by suppressing the nucleation of amyloid fibrils and increases the solubility of amyloid-prone proteins. These dual effects on kinetics and equilibrium are related to the unusually high chemical potential of DNAJB6b in solution. As a consequence, the chaperone alone forms highly polydisperse oligomers, whereas in a mixture with an amyloid-forming protein or peptide it may form co-aggregates to gain a reduced chemical potential, thus enabling the amyloid peptide to increase its chemical potential leading to enhanced solubility of the peptide. Understanding such action at the level of molecular driving forces and detailed structures requires access to highly pure and sequence homogeneous DNAJB6b with no sequence extension. We therefore outline here an expression and purification protocol of the protein "as is" with no tags leading to very high levels of pure protein based on its physicochemical properties, including size and charge. The versatility of the protocol is demonstrated through the expression of an isotope labelled protein and seven variants, and the purification of three of these. The activity of the protein is bench-marked using aggregation assays. Two of the variants are used to produce a palette of fluorescent DNAJB6b labelled at an engineered N- or C-terminal cysteine.

(More than) doubling down: Effective fibrinolysis at a reduced rt-PA dose for catheter-directed thrombolysis combined with histotripsy

Deep vein thrombosis is a major source of morbidity and mortality worldwide. For acute proximal deep vein thrombosis, catheter-directed thrombolytic therapy is an accepted method for vessel recanalization. Thrombolytic therapy is not without risk, including the potential for hemorrhagic bleeding that increases with lytic dose. Histotripsy is a focused ultrasound therapy that generates bubble clouds spontaneously in tissue at depth. The mechanical activity of histotripsy increases the efficacy of thrombolytic therapy at doses consistent with current pharmacomechanical treatments for venous thrombosis. The objective of this study was to determine the influence of lytic dose on histotripsy-enhanced fibrinolysis. Human whole blood clots formed in vitro were exposed to histotripsy and a thrombolytic agent (recombinant tissue plasminogen activator, rt-PA) in a venous flow model perfused with plasma. Lytic was administered into the clot via an infusion catheter at concentrations ranging from 0 (control) to 4.54 μg/mL (a common clinical dose for catheter-directed thrombolysis). Following treatment, perfusate samples were assayed for markers of fibrinolysis, hemolysis, and intact red blood cells and platelets. Fibrinolysis was equivalent between the common clinical dose of rt-PA (4.54 μg/mL) and rt-PA at a reduction to one-twentieth of the common clinical dose (0.23 μg/mL) when combined with histotripsy. Minimal changes were observed in hemolysis for treatment arms with or without histotripsy, potentially due to clot damage from insertion of the infusion catheter. Likewise, histotripsy did not increase the concentration of red blood cells or platelets in the perfusate following treatment compared to rt-PA alone. At the highest lytic dose, a refined histotripsy exposure scheme was implemented to cover larger areas of the clot. The updated exposure scheme improved clot mass loss and fibrinolysis relative to administration of lytic alone. Overall, the data collected in this study indicate the rt-PA dose can be reduced by more than a factor of ten and still promote fibrinolysis when combined with histotripsy.

Functional analysis and regulation mechanism of interferon gamma in macrophages of large yellow croaker (Larimichthys crocea)

Interferon gamma (IFN-γ) is a widely expressed cytokine that has potent antiviral and immunomodulatory effects. The expression and bioactivity of IFN-γ have been reported in several fish species. However, the molecular mechanism mediated by IFN-γ in fish macrophages has not been completely elucidated. This study used the macrophage cell line to investigate the functional activities and regulation mechanism of large yellow croaker IFN-γ (LcIFN-γ). Herein, the mRNA expression of Lcifn-γ was significantly upregulated in macrophages after LPS and poly(I:C) treatment. Recombinant LcIFN-γ protein (rLcIFN-γ) significantly enhanced the phagocytic ability and respiratory burst activity of macrophages. Meanwhile, rLcIFN-γ induced M1 phenotype polarization of macrophages with the upregulated expressions of pro-inflammatory gene. Moreover, rLcIFN-γ upregulated the IFN-stimulated genes (ISGs) expression and activated JAK (Janus tyrosine kinases)-STAT (signal transducer and activator of transcription) signaling pathway by causing the phosphorylation of JAK1 and STAT1^Tyr701. Furthermore, the promoter activity of IFN-regulatory factor 1 (IRF1) was significantly upregulated by the phosphorylated transcription factor STAT1 through binding to its promoter region. In addition to the classical JAK-STAT pathway, rLcIFN-γ also activated multiple distinct signaling cascades such as mitogen-activated protein kinase (MAPK) and protein kinase B (AKT) pathways. Overall, this study indicated the powerful effects of LcIFN-γ on macrophage activation of large yellow croaker and its molecular mechanism.

Structural and functional insights into the first Bacillus thuringiensis vegetative insecticidal protein of the Vpb4 fold, active against western corn rootworm

The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, is a major maize pest in the United States causing significant economic loss. The emergence of field-evolved resistant WCR to Bacillus thuringiensis (Bt) traits has prompted the need to discover and deploy new insecticidal proteins in transgenic maize. In the current study we determined the crystal structure and mode of action (MOA) of the Vpb4Da2 protein (formerly known as Vip4Da2) from Bt, the first identified insecticidal Vpb4 protein with commercial level control against WCR. The Vpb4Da2 structure exhibits a six-domain architecture mainly comprised of antiparallel β-sheets organized into β-sandwich layers. The amino-terminal domains 1-3 of the protein share structural homology with the protective antigen (PA) PA14 domain and encompass a long β-pore forming loop as in the clostridial binary-toxB module. Domains 5 and 6 at the carboxyl-terminal half of Vpb4Da2 are unique as this extension is not observed in PA or any other structurally-related protein other than Vpb4 homologs. These unique Vpb4 domains adopt the topologies of carbohydrate-binding modules known to participate in receptor-recognition. Functional assessment of Vpb4Da2 suggests that domains 4-6 comprise the WCR receptor binding region and are key in conferring the observed insecticidal activity against WCR. The current structural analysis was complemented by in vitro and in vivo characterizations, including immuno-histochemistry, demonstrating that Vpb4Da2 follows a MOA that is consistent with well-characterized 3-domain Bt insecticidal proteins despite significant structural differences.

Purification of full-length recombinant human huntingtin proteins with allelic series of polyglutamine lengths

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by the polyglutamine (polyQ) expansion in huntingtin (HTT) protein. The challenge of obtaining full-length HTT proteins with high purity limits the understanding of the HTT protein function. Here, we provide a protocol to generate and purify full-length recombinant human HTT proteins with various polyQ lengths, which is key to investigate the biochemical function of HTT proteins and the molecular mechanism underlying HD pathology. For complete details on the use and execution of this protocol, please refer to Jung et al. (2020).

A low-cost and open-source protocol to produce key enzymes for molecular detection assays

Here, we describe a detailed step-by-step protocol for the expression, purification, quantification, and activity determination of key enzymes for molecular detection of pathogens. Based on previous reports, we optimized the protocol for LbCas12a, Taq DNA polymerase, M-MLV reverse transcriptase, and TEV protease to make it compatible with minimal laboratory equipment, broadly available in low- and middle-income countries. The enzymes produced with this protocol have been successfully used for molecular detection applications. For complete details on the use and execution of this protocol, please refer to Alcántara et al. (2021a, 2021b).

Development of a Kit for Rapid Immunochromatographic Detection of Sacbrood Virus Infecting Apis cerana (AcSBV) Based on Polyclonal and Monoclonal Antibodies Raised against Recombinant VP1 and VP2 Expressed in Escherichia coli

A Korean isolate of the sacbrood virus infecting Apis cerana (AcSBV-Kor) is the most destructive honeybee virus, causing serious economic damage losses in Korean apiculture. To address this, here, we attempted to develop an assay for the rapid detection of AcSBV-Kor based on immunochromatographic detection of constituent viral proteins. Genes encoding VP1 and VP2 proteins of AcSBV-Kor were cloned into an expression vector (pET-28a) and expressed in Escherichia coli BL21(DE3). During purification, recombinant VP1 (rVP1) and VP2 (rVP2) proteins were found in the insoluble fraction, with a molecular size of 26.7 and 24.9 kDa, respectively. BALB/c mice immunized with the purified rVP1 and rVP2 produced polyclonal antibodies (pAbs) such as pAb-rVP1 and pAb-rVP2. Western blot analysis showed that pAb-rVP1 strongly reacted with the homologous rVP1 but weakly reacted with heterologous rVP2. However, pAb-rVP2 strongly reacted not only with the homologous rVP2 but also with the heterologous rVP1. Spleen cells of the immunized mice fused with SP2/0-Ag14 myeloma cells produced monoclonal antibodies (mAbs) such as mAb-rVP1-1 and mAb-rVP2-13. Western blot analysis indicated that pAb-rVP1, pAb-rVP2, mAb-rVP1-1, and mAb-rVP2-13 reacted with AcSBV-infected honeybees and larvae as well as the corresponding recombinant proteins. These antibodies were then used in the development of a rapid immunochromatography (IC) strip assay kit with colloidal gold coupled to pAb-rVP1 and pAb-rVP2 at the conjugate pad and mAb-rVP1-1 and mAb-rVP2-13 at the test line. One antibody pair, pAb-rVP1/mAb-VP1-1, showed positive reactivity as low as 1.38 × 10³ copies, while the other pair, pAb-rVP2/mAb-VP2-13, showed positive reactivity as low as 1.38 × 10⁴ copies. Therefore, the antibody pair pAb-rVP1/mAb-VP1-1 was selected as a final candidate for validation. To validate the detection of AcSBV, the IC strip tests were conducted with 50 positive and 50 negative samples and compared with real-time PCR tests. The results confirm that the developed IC assay is a sufficiently sensitive and specific detection method for user-friendly and rapid detection of AcSBV.

High-yield synthesis and purification of recombinant human GABA transaminase for high-throughput screening assays

Many studies have focussed on modulating the activity of γ-aminobutyric acid transaminase (GABA-T), a GABA-catabolizing enzyme, for treating neurological diseases, such as epilepsy and drug addiction. Nevertheless, human GABA-T synthesis and purification have not been established. Thus, biochemical and drug design studies on GABA-T have been performed by using porcine GABA-T mostly and even bacterial GABA-T. Here we report an optimised protocol for overexpression of 6xHis-tagged human GABA-T in human cells followed by a two-step protein purification. Then, we established an optimised human GABA-T (0.5 U/mg) activity assay. Finally, we compared the difference between human and bacterial GABA-T in sensitivity to two irreversible GABA-T inhibitors, gabaculine and vigabatrin. Human GABA-T in homodimeric form showed 70-fold higher sensitivity to vigabatrin than bacterial GABA-T in multimeric form, indicating the importance of using human GABA-T. In summary, our newly developed protocol can be an important first step in developing more effective human GABA-T modulators.

Fast and Specific Peroxygenase Reactions Catalyzed by Fungal Mono-Copper Enzymes

The copper-dependent lytic polysaccharide monooxygenases (LPMOs) are receiving attention because of their role in the degradation of recalcitrant biomass and their intriguing catalytic properties. The fundamentals of LPMO catalysis remain somewhat enigmatic as the LPMO reaction is affected by a multitude of LPMO- and co-substrate-mediated (side) reactions that result in a complex reaction network. We have performed kinetic studies with two LPMOs that are active on soluble substrates, NcAA9C and LsAA9A, using various reductants typically employed for LPMO activation. Studies with NcAA9C under "monooxygenase" conditions showed that the impact of the reductant on catalytic activity is correlated with the hydrogen peroxide-generating ability of the LPMO-reductant combination, supporting the idea that a peroxygenase reaction is taking place. Indeed, the apparent monooxygenase reaction could be inhibited by a competing H2O2-consuming enzyme. Interestingly, these fungal AA9-type LPMOs were found to have higher oxidase activity than bacterial AA10-type LPMOs. Kinetic analysis of the peroxygenase activity of NcAA9C on cellopentaose revealed a fast stoichiometric conversion of high amounts of H2O2 to oxidized carbohydrate products. A kcat value of 124 ± 27 s-1 at 4 °C is 20 times higher than a previously described kcat for peroxygenase activity on an insoluble substrate (at 25 °C) and some 4 orders of magnitude higher than typical "monooxygenase" rates. Similar studies with LsAA9A revealed differences between the two enzymes but confirmed fast and specific peroxygenase activity. These results show that the catalytic site arrangement of LPMOs provides a unique scaffold for highly efficient copper redox catalysis.

Expression, purification and structural characterization of resveratrol synthase from Polygonum cuspidatum

Polygonum cuspidatum, an important medicinal plant in China, is a rich source of resveratrol compounds, and its synthesis related resveratrol synthase (RS) gene is highly expressed in stems. The sequence of the resveratrol synthase was amplified with specific primers. Sequence comparison showed that it was highly homologous to the STSs. The RS gene of Polygonum cuspidatum encodes 389 amino acids and has a theoretical molecular weight of 42.4 kDa, which is called PcRS1. To reveal the molecular basis of the synthesized resveratrol activity of PcRS1, we expressed the recombinant protein of full-length PcRS1 in Escherichia coli, and soluble protein products were produced. The collected products were purified by Ni-NTA chelation chromatography and appeared as a single band on SDS-PAGE. In order to obtain higher purity PcRS1, SEC was used to purify the protein and sharp single peak, and DLS detected that the aggregation state of protein molecules was homogeneous and stable. In order to verify the enzyme activity of the high-purity PcRS1, the reaction product was detected at 303 nm. By predicting the structural information of monomer PcRS1 and PcRS1 ligand complexes, we analyzed the ligand binding pocket and protein surface electrostatic potential of the complex, and compared it with the highly homologous STSs protein structures of the iso-ligand. New structural features of protein evolution are proposed. PcRS1 obtained a more complete configuration and the optimal orientation of the active site residues, thus improving its catalytic capacity in resveratrol synthesis.

Recombinant production of a functional SARS-CoV-2 spike receptor binding domain in the green algae Chlamydomonas reinhardtii

Recombinant production of viral proteins can be used to produce vaccine antigens or reagents to identify antibodies in patient serum. Minimally, these proteins must be correctly folded and have appropriate post-translation modifications. Here we report the production of the SARS-CoV-2 spike protein Receptor Binding Domain (RBD) in the green algae Chlamydomonas. RBD fused to a fluorescent reporter protein accumulates as an intact protein when targeted for ER-Golgi retention or secreted from the cell, while a chloroplast localized version is truncated. The ER-retained RBD fusion protein was able to bind the human ACE2 receptor, the host target of SARS-CoV-2, and was specifically out-competed by mammalian cell-produced recombinant RBD, suggesting that the algae produced proteins are sufficiently post-translationally modified to act as authentic SARS-CoV-2 antigens. Because algae can be grown at large scale very inexpensively, this recombinant protein may be a low cost alternative to other expression platforms.

The moonlighting protein fructose 1,6-bisphosphate aldolase as a potential vaccine candidate against Photobacterium damselae subsp. piscicida in Asian sea bass (Lates calcarifer)

Vaccination is the most effective, safe, and environmentally friendly method to prevent the outbreak of Photobacterium damselae subsp. piscicida (Phdp), a dangerous pathogen in aquaculture worldwide. Here, recombinant proteins of catalase, superoxide dismutase, isocitrate dehydrogenase, fructose 1,6-bisphosphate aldolase (Fba), and a mixture of all four proteins were investigated for their immunoprotective effects against photobacteriosis in Asian sea bass (Lates calcarifer). After immunization, experimental fish showed an increase in specific antibody levels and lysozyme activities, especially the Fba group. After a lethal challenge with Phdp strain AOD105021, the Fba group achieved the highest relative percentage of survival rate (70.21%) and a significantly lower bacterial load in the spleens than other groups 3 days after infection. The results suggest that Fba is a good candidate for subunit vaccine development against photobacteriosis in fish.

Comparison of CD20 Binding Affinities of Rituximab Produced in Nicotiana benthamiana Leaves and Arabidopsis thaliana Callus

Plants are promising drug-production platforms with high economic efficiency, stability, and convenience in mass production. However, studies comparing the equivalency between the original antibodies and those produced in plants are limited. Amino acid sequences that constitute the Fab region of an antibody are diverse, and the post-transcriptional modifications that occur according to these sequences in animals and plants are also highly variable. In this study, rituximab, a blockbuster antibody drug used in the treatment of non-Hodgkin's lymphoma, was produced in Nicotiana benthamiana leaves and Arabidopsis thaliana callus, and was compared to the original rituximab produced in CHO cells. Interestingly, the epitope recognition and antigen-binding abilities of rituximab from N. benthamiana leaves were almost lost. In the case of rituximab produced in A. thaliana callus, the specific binding ability and CD20 capping activity were maintained, but the binding affinity was less than 50% of that of original rituximab from CHO cells. These results suggest that different plant species exhibit different binding affinities. Accordingly, in addition to the differences in PTMs between mammals and plants, the differences between the species must also be considered in the process of producing antibodies in plants.

Molecular identification of peptidoglycan recognition protein 5 and its functional characterization in innate immunity of large yellow croaker, Larimichthys crocea

Fish peptidoglycan recognition proteins (PGRPs) play important roles in microbial recognition, and bacterial elimination. In the present study, a short-type PGRP from large yellow croaker, LcPGRP5 was cloned and its functions were characterized. LcPGRP5 gene encodes a protein containing conserved PGRP domain, but no signal peptide. Phylogenetic analysis shows that LcPGRP5 is clustered with other short PGRPs identified in other teleosts. LcPGRP5 is constitutively expressed in all tissues examined, with the highest expression being detected in the head kidney. Recombinant LcPGRP5 protein features amidase activity and bactericidal activity. Notably, LcPGRP5 could enhance the phagocytosis of the bacteria by large yellow croaker macrophage, with higher phagocytic capacity being observed in Staphylococcus aureus compared to Escherichia coli. Moreover, overexpression of LcPGRP5 suppresses pro-inflammatory effects elicited by bacterial exposure in the macrophage cell line. Overall, the present results clearly indicate the important roles of LcPGRP5 played in the innate immune responses against bacterial infection.

A highly efficient method for the production and purification of recombinant human CXCL8

Chemokines play diverse and fundamental roles in the immune system and human disease, which has prompted their structural and functional characterisation. Production of recombinant chemokines that are folded and bioactive is vital to their study but is limited by the stringent requirements of a native N-terminus for receptor activation and correct disulphide bonding required to stabilise the chemokine fold. Even when expressed as fusion proteins, overexpression of chemokines in E. coli tends to result in the formation of inclusion bodies, generating the additional steps of solubilisation and refolding. Here we present a novel method for producing soluble chemokines in relatively large amounts via a simple two-step purification procedure with no requirements for refolding. CXCL8 produced by this method has the correct chemokine fold as determined by NMR spectroscopy and in chemotaxis assays was indistinguishable from commercially available chemokines. We believe that this protocol significantly streamlines the generation of recombinant chemokines.

Optimized expression and purification of adipose triglyceride lipase improved hydrolytic and transacylation activities in vitro

Adipose triglyceride lipase (ATGL) plays a key role in intracellular lipolysis, the mobilization of stored triacylglycerol. This work provides an important basis for generating reproducible and detailed data on the hydrolytic and transacylation activities of ATGL. We generated full-length and C-terminally truncated ATGL variants fused with various affinity tags and analyzed their expression in different hosts, namely E.coli, the insect cell line Sf9, and the mammalian cell line human embryonic kidney 293T. Based on this screen, we expressed a fusion protein of ATGL covering residues M1-D288 flanked with N-terminal and C-terminal purification tags. Using these fusions, we identified key steps in expression and purification protocols, including production in the E. coli strain ArcticExpress (DE3) and removal of copurified chaperones. The resulting purified ATGL variant demonstrated improved lipolytic activity compared with previously published data, and it could be stimulated by the coactivator protein comparative gene identification-58 and inhibited by the protein G0/G1 switch protein 2. Shock freezing and storage did not affect the basal activity but reduced coactivation of ATGL by comparative gene identification 58. In vitro, the truncated ATGL variant demonstrated acyl-CoA-independent transacylation activity when diacylglycerol was offered as substrate, resulting in the formation of fatty acid as well as triacylglycerol and monoacylglycerol. However, the ATGL variant showed neither hydrolytic activity nor transacylation activity upon offering of monoacylglycerol as substrate. To understand the role of ATGL in different physiological contexts, it is critical for future studies to identify all its different functions and to determine under what conditions these activities occur.

Development of a Platform for Producing Recombinant Protein Components of Epitope Vaccines for the Prevention of COVID-19

A new platform for creating anti-coronavirus epitope vaccines has been developed. Two loop-like epitopes with lengths of 22 and 42 amino acid residues were selected from the receptor-binding motif of the Spike protein from the SARS‑CoV‑2 virus that participate in a large number of protein-protein interactions in the complexes with ACE2 and neutralizing antibodies. Two types of hybrid proteins, including one of the two selected epitopes, were constructed. To fix conformation of the selected epitopes, an approach using protein scaffolds was used. The homologue of Rop protein from the Escherichia coli ColE1 plasmid containing helix-turn-helix motif was used as an epitope scaffold for the convergence of C- and N-termini of the loop-like epitopes. Loop epitopes were inserted into the turn region. The conformation was additionally fixed by a disulfide bond formed between the cysteine residues present within the epitopes. For the purpose of multimerization, either aldolase from Thermotogamaritima, which forms a trimer in solution, or alpha-helical trimerizer of the Spike protein from SARS‑CoV‑2, was attached to the epitopes incorporated into the Rop-like protein. To enable purification on the heparin-containing sorbents, a short fragment from the heparin-binding hemagglutinin of Mycobacterium tuberculosis was inserted at the C-terminus of the hybrid proteins. All the obtained proteins demonstrated high level of immunogenicity after triplicate parenteral administration to mice. Sera from the mice immunized with both aldolase-based hybrid proteins and the Spike protein SARS‑CoV‑2 trimerizer-based protein with a longer epitope interacted with both the inactivated SARS‑CoV‑2 virus and the Spike protein receptor-binding domain at high titers.

Acyl Chain Specificity of Marine Streptomyces klenkii PhosPholipase D and Its Application in Enzymatic Preparation of Phosphatidylserine

Mining of phospholipase D (PLD) with altered acyl group recognition except its head group specificity is also useful in terms of specific acyl size phospholipid production and as diagnostic reagents for quantifying specific phospholipid species. Microbial PLDs from Actinomycetes, especially Streptomyces, best fit this process requirements. In the present studies, a new PLD from marine Streptomyces klenkii (SkPLD) was purified and biochemically characterized. The optimal reaction temperature and pH of SkPLD were determined to be 60 °C and 8.0, respectively. Kinetic analysis showed that SkPLD had the relatively high catalytic efficiency toward phosphatidylcholines (PCs) with medium acyl chain length, especially 12:0/12:0-PC (67.13 S-1 mM-1), but lower catalytic efficiency toward PCs with long acyl chain (>16 fatty acids). Molecular docking results indicated that the different catalytic efficiency was related to the increased steric hindrance of long acyl-chains in the substrate-binding pockets and differences in hydrogen-bond interactions between the acyl chains and substrate-binding pockets. The enzyme displayed suitable transphosphatidylation activity and the reaction process showed 26.18% yield with L-serine and soybean PC as substrates. Present study not only enriched the PLD enzyme library but also provide guidance for the further mining of PLDs with special phospholipids recognition properties.

A prokaryote system optimization for rMEPLox expression: A promising non-toxic antigen for Loxosceles antivenom production

Loxoscelism is the most dangerous araneism form in Brazil and antivenom therapy is the recommended treatment. Antivenom is produced by horse immunization with Loxosceles spider venom, which is toxic for the producer animal. Moreover, due to the high amount of venom required for horse hyperimmunization, new strategies for antigens obtention have been proposed. In this sense, our research group has previously produced a non-toxic recombinant multiepitopic protein derived from Loxosceles toxins (rMEPLox). rMEPLox was a successful immunogen, being able to induce the production of neutralizing antibodies, which could be used in the Loxoscelism treatment. However, rMEPLox obtention procedure requires optimization, as its production needs to be scaled up to suit antivenom manufacture. Therefore, an effective protocol development for rMEPlox production would be advantageous. To achieve this objective, we evaluated the influence of different cultivation conditions for rMEPLox optimum expression. The optimum conditions to obtain large amounts of rMEPlox were defined as the use of C43(DE3)pLysS as a host strain, 2xTY medium, 0.6 mM IPTG, biomass pre induction of OD600nm = 0.4 and incubation at 30 °C for 16 h. Following the optimized protocol, 39.84 mg/L of soluble rMEPLox was obtained and tested as immunogen. The results show that the obtained rMEPLox preserved the previously described immunogenicity, and it was able to generate antibodies that recognize different epitopes of the main Loxosceles venom toxins, which makes it a promising candidate for the antivenom production for loxoscelism treatment.

Redox status of cysteines does not alter functional properties of human dUTPase but the Y54C mutation involved in monogenic diabetes decreases protein stability

Recently it was proposed that the redox status of cysteines acts as a redox switch to regulate both the oligomeric status and the activity of human dUTPase. In a separate report, a human dUTPase point mutation, resulting in a tyrosine to cysteine substitution (Y54C) was identified as the monogenic cause of a rare syndrome associated with diabetes and bone marrow failure. These issues prompt a critical investigation about the potential regulatory role of cysteines in the enzyme. Here we show on the one hand that independently of the redox status of wild-type cysteines, human dUTPase retains its characteristic trimeric assembly and its catalytic activity. On the other hand, the Y54C mutation did not compromise the substrate binding and the catalytic properties of the enzyme at room temperature. The thermal stability of the mutant protein was found to be decreased, which resulted in the loss of 67% of its activity after 90 min incubation at the physiological temperature in contrast to the wild-type enzyme. In addition, the presence or absence of reducing agents had no effect on hDUTY54C activity and stability, although it was confirmed that the introduced cysteine contains a solvent accessible thiol group.

Characterization of a Novel Phage ΦAb1656-2 and Its Endolysin with Higher Antimicrobial Activity against Multidrug-Resistant Acinetobacter baumannii

Acinetobacter baumannii is a nosocomial pathogen, which is a problem worldwide due to the emergence of a difficult-to-treat multidrug-resistant A. baumannii (MDRAB). Endolysins are hydrolytic enzymes produced by a bacteriophage that can be used as a potential therapeutic agent for multidrug-resistant bacterial infection in replacing antibiotics. Here, we isolated a novel bacteriophage through prophage induction using mitomycin C from clinical A. baumannii 1656-2. Morphologically, ΦAb1656-2 was identified as a Siphoviridae family bacteriophage, which can infect MDRAB. The whole genome of ΦAb1656-2 was sequenced, and it showed that it is 50.9 kb with a G + C content of 38.6% and 68 putative open reading frames (ORFs). A novel endolysin named AbEndolysin with an N-acetylmuramidase-containing catalytic domain was identified, expressed, and purified from ΦAb1656-2. Recombinant AbEndolysin showed significant antibacterial activity against MDRAB clinical strains without any outer membrane permeabilizer. These results suggest that AbEndolysin could represent a potential antimicrobial agent for treating MDRAB clinical isolates.

Characterization and engineering of Streptomyces griseofuscus DSM 40191 as a potential host for heterologous expression of biosynthetic gene clusters

Streptomyces griseofuscus DSM 40191 is a fast growing Streptomyces strain that remains largely underexplored as a heterologous host. Here, we report the genome mining of S. griseofuscus, followed by the detailed exploration of its phenotype, including the production of native secondary metabolites and ability to utilise carbon, nitrogen, sulphur and phosphorus sources. Furthermore, several routes for genetic engineering of S. griseofuscus were explored, including use of GusA-based vectors, CRISPR-Cas9 and CRISPR-cBEST-mediated knockouts. Two out of the three native plasmids were cured using CRISPR-Cas9 technology, leading to the generation of strain S. griseofuscus DEL1. DEL1 was further modified by the full deletion of a pentamycin BGC and an unknown NRPS BGC, leading to the generation of strain DEL2, lacking approx. 500 kbp of the genome, which corresponds to a 5.19% genome reduction. DEL2 can be characterized by faster growth and inability to produce three main native metabolites: lankacidin, lankamycin, pentamycin and their derivatives. To test the ability of DEL2 to heterologously produce secondary metabolites, the actinorhodin BGC was used. We were able to observe a formation of a blue halo, indicating a potential production of actinorhodin by both DEL2 and a wild type.

Construction of a eukaryotic expression system with stable and secretory expression of mycobacterium tuberculosis 38 kDa protein

The 38 kDa protein is a major antigen of mycobacterium tuberculosis and has been widely used in TB serodiagnosis, due to its highly sensitivity and specificity. Here we attempt to establish a production platform of recombinant 38 kDa protein in mammalian cells and to evaluate the potential value of 38 kDa protein in TB serodiagnosis. The 38 kDa gene is synthesized and cloned into a lentiviral expressing vector. Recombinant lentiviral vector LV-CMV-38 kDa-eGFP was packaged, titered, and then transduced into HEK 293 T cells. Recombinant cell lines were selected by limiting dilution. Supernatants were collected and purified by HisTrapTM HP column. Western blot showed a molecular weight of approximate 38 kDa in cell supernatants as expected. ELISA assay confirmed the immunological specificity of the obtained protein in the presence of MTB-infected human serum samples. In all, we have obtained a stable cell line with long-term and robust expression of secretory MTB 38 kDa protein, which may provide a promising candidate antigen for the development of TB serological diagnosis.

Discovery of a new light-driven Li+/Na+-pumping rhodopsin with DTG motif

Microbial pumping rhodopsin is a seven-transmembrane retinal binding protein, which is light-driven ion pump with a functional key motif. Ion-pumping with the key motif and charged amino acids in the rhodopsin is biochemically important. The rhodopsins with DTG motif have been discovered in various eubacteria, and they function as H⁺ pump. Especially, the DTG motif rhodopsins transported H⁺ despite the replacement of a proton donor by Gly. We investigated Methylobacterium populi rhodopsin (MpR) in one of the DTG motif rhodopsin clades. To determine which ions the MpR transport, we tested with various monovalent ion solutions and determined that MpR transports Li⁺/Na⁺. By replacing the three negatively charged residues residues which are located in helix B, Glu32, Glu33, and Asp35, we concluded that the residues play a critical role in the transport of Li⁺/Na⁺. The MpR E33Q transported H⁺ in place of Li⁺/Na⁺, suggesting that Glu33 is a Li⁺/Na⁺ binding site on the cytoplasmic side. Gly93 in MpR was replaced by Asp to convert from the Li⁺/Na⁺ pump to the H⁺ pump, resulting in MpR G93D transporting H⁺. Dissociation constant (K_d) values of Na⁺ for MpR WT and E33Q were determined to be 4.0 and 72.5 mM, respectively. These results indicated the mechanism by which MpR E33Q transports H⁺. Up to now, various ion-pumping rhodopsins have been discovered, and Li⁺/Na⁺-pumping rhodopsins were only found in the NDQ motif in NaR. Here, we report a new light-driven Na⁺ pump MpR and have determined the important residues required for Li⁺/Na⁺-pumping different from previously known NaR.

Selective activation of PFKL suppresses the phagocytic oxidative burst

In neutrophils, nicotinamide adenine dinucleotide phosphate (NADPH) generated via the pentose phosphate pathway fuels NADPH oxidase NOX2 to produce reactive oxygen species for killing invading pathogens. However, excessive NOX2 activity can exacerbate inflammation, as in acute respiratory distress syndrome (ARDS). Here, we use two unbiased chemical proteomic strategies to show that small-molecule LDC7559, or a more potent designed analog NA-11, inhibits the NOX2-dependent oxidative burst in neutrophils by activating the glycolytic enzyme phosphofructokinase-1 liver type (PFKL) and dampening flux through the pentose phosphate pathway. Accordingly, neutrophils treated with NA-11 had reduced NOX2-dependent outputs, including neutrophil cell death (NETosis) and tissue damage. A high-resolution structure of PFKL confirmed binding of NA-11 to the AMP/ADP allosteric activation site and explained why NA-11 failed to agonize phosphofructokinase-1 platelet type (PFKP) or muscle type (PFKM). Thus, NA-11 represents a tool for selective activation of PFKL, the main phosphofructokinase-1 isoform expressed in immune cells.

Identification and In Silico Characterization of Novel Helicobacter pylori Glucose-6-Phosphate Dehydrogenase Inhibitors

Helicobacter pylori (H. pylori) is a pathogen that can remain in the stomach of an infected person for their entire life. As a result, this leads to the development of severe gastric diseases such as gastric cancer. In addition, current therapies have several problems including antibiotics resistance. Therefore, new practical options to eliminate this bacterium, and its induced affections, are required to avoid morbidity and mortality worldwide. One strategy in the search for new drugs is to detect compounds that inhibit a limiting step in a central metabolic pathway of the pathogen of interest. In this work, we tested 55 compounds to gain insights into their possible use as new inhibitory drugs of H. pylori glucose-6-phosphate dehydrogenase (HpG6PD) activity. The compounds YGC-1; MGD-1, MGD-2; TDA-1; and JMM-3 with their respective scaffold 1,3-thiazolidine-2,4-dione; 1H-benzimidazole; 1,3-benzoxazole, morpholine, and biphenylcarbonitrile showed the best inhibitory activity (IC₅₀ = 310, 465, 340, 204 and 304 μM, respectively). We then modeled the HpG6PD protein by homology modeling to conduct an in silico study of the chemical compounds and discovers its possible interactions with the HpG6PD enzyme. We found that compounds can be internalized at the NADP⁺ catalytic binding site. Hence, they probably exert a competitive inhibitory effect with NADP⁺ and a non-competitive or uncompetitive effect with G6P, that of the compounds binding far from the enzyme’s active site. Based on these findings, the tested compounds inhibiting HpG6PD represent promising novel drug candidates against H. pylori.

Expression and purification of recombinant alpha-toxin AnCra1 from the scorpion Androctonus crassicauda and its functional characterization on mammalian sodium channels

BACKGROUND

Alpha-scorpion toxins with long-chain peptide and four disulfide bonds represent diverse pharmacological profiles for various subtypes of voltage-gated sodium channels. Obtaining the natural toxins are difficult and time-consuming process, which represents the major difficulty to interpreting analysis of their structural and functional properties.

METHODS AND RESULTS

This study describes the toxin peptide and plasmid construct containing the gene coding for mammalian toxin AnCra1 from the scorpion Androctonus crassicauda venom. We have established genetic construction of fusion protein in pET32a + vector containing thioredoxin (Trx-tag), enterokinase cleavage site and 6xhistidine-tag for efficient expression in Escherichia coli strain RG2 (DE3). The soluble expressed peptide, then purified by Ni-NTA resin affinity chromatography and its purity was confirmed by reverse-phase HPLC and mass spectrometry (7433.54 Da.). The electrophysiological data showed that recombinant AnCra1 selectively inhibits the fast inactivation of hNav1.7 channel (EC₅₀ = 136.7 ± 6.6 nM).

CONCLUSIONS

Our findings demonstrate that the AnCra1 is structurally and functionally analogous to alpha excitatory toxins; furthermore, expression and purification of bioactive scorpion toxins in bacterial cells can be a practicable and efficient way to obtain a novel source of toxin peptides as tools to study the function and physiological responses of ion channels.

Cytotoxicity of Frutalin on Distinct Cancer Cells Is Independent of Its Glycosylation

Frutalin is a plant lectin with beneficial immunobiological action, although the access to its active form is still restricted. Moreover, there is a knowledge gap on isoform activity and glycosylation impact on its bioactivity, and recombinant production protocols were seen as ineffective. Here, a simpler and faster production and purification protocol was developed, attaining a yield of purified frutalin 3.3-fold higher than that obtained previously. Hemagglutination assays confirmed that this frutalin isoform could not agglutinate rabbit erythrocytes, while maintaining the native tetrameric structure, as indicated by DLS analysis, and strong interaction with methyl-alpha-galactose, in fluorescence spectroscopy studies. The cytotoxicity of the recombinant frutalin isoform was shown in a broad panel of human cancer cells: colon (HCT116), melanoma (A375), triple-negative breast cancer (MDA-MB-231), and ovarian (IGROV-1). Treatment with 8.5–11.8 μM TrxFTL reduced proliferation of all cancer cells to half in 48 h. This anti-proliferative effect encompasses the p53 pathway since it was significantly reduced in p53-null colon cancer cells (HCT116 p53^−/−; GI₅₀ of 25.0 ± 3.0 μM), when compared to the isogenic p53-positive cells (HCT116 p53^+/+; GI₅₀ of 8.7 ± 1.8 μM; p < 0.002). This recombinantly produced frutalin isoform has relevant cytotoxic effect and its biological activity is not dependent on glycosylation. The developed E. coli production and purification protocol generates high yield of non-glycosylated frutalin isoform with potent cytotoxic activity, enabling the development of novel anticancer p53-targeting therapies.

Neutrophil functions can be regulated by IL-35, which is mainly expressed in IL-15Rα+ cells in grass carp (Ctenopharyngodon idella)

IL-35 plays a key role in regulatory T (Treg) and regulatory B (Breg) cell functions in mammals. CD25 has been demonstrated as one of the markers of Treg cells, and CD19⁺CD25^hiCD71^hi cells have been verified as a type of Breg cells in humans. These results indicate that there is a close relationship between IL-35 and CD25⁺ cells. In mammals, CD25 (alias IL-2Rα) has been identified as having high affinity and specificity for IL-2 binding, and is closely linked and structurally related to IL-15Rα, which having high affinity for IL-15 binding. In teleost, IL-15Rα can bind to both IL-2 and IL-15, with higher affinity to IL-15 than IL-2, and has been termed a CD25-like molecule in some research studies. To date, no studies of IL-35 and IL-15Rα have been documented in fish. In this work, five isoforms of IL-15Rα were cloned from grass carp, and a monoclonal antibody to the protein was developed. The results of flow cytometry and quantitative real-time PCR analyses demonstrated that grass carp IL-35 subunit genes EBI3a and IL-12p35 were mainly expressed in IL-15Rα⁺ cells, while the expression levels of IL-10 and TGF-β in IL-15Rα⁺ and IL-15Rα^- cells were insignificant. Recombinant grass carp IL-35 (rgcIL-35) could increase the proportion of IL-15Rα⁺ cells in leukocytes, and a certain proportion of IL-15Rα⁺ cells also appeared in myeloid cell subset II after stimulation with rgcIL-35. Meanwhile, the migration, phagocytic ability, and bactericidal ability of grass carp neutrophils were significantly decreased after stimulation with certain concentrations of rgcIL-35. Moreover, neutrophil apoptosis could be significantly inhibited by rgcIL-35.

Production of functional human fetal hemoglobin in Nicotiana benthamiana for development of hemoglobin-based oxygen carriers

Hemoglobin-based oxygen carriers have long been pursued to meet clinical needs by using native hemoglobin (Hb) from human or animal blood, or recombinantly produced Hb, but the development has been impeded by safety and toxicity issues. Herewith we report the successful production of human fetal hemoglobin (HbF) in Nicotiana benthamiana through Agrobacterium tumefaciens-mediated transient expression. HbF is a heterotetrameric protein composed of two identical α- and two identical γ-subunits, held together by hydrophobic interactions, hydrogen bonds, and salt bridges. In our study, the α- and γ-subunits of HbF were fused in order to stabilize the α-subunits and facilitate balanced expression of α- and γ-subunits in N. benthamiana. Efficient extraction and purification methods enabled production of the recombinantly fused endotoxin-free HbF (rfHbF) in high quantity and quality. The transiently expressed rfHbF protein was identified by SDS-PAGE, Western blot and liquid chromatography-tandem mass spectrometry analyses. The purified rfHbF possessed structural and functional properties similar to native HbF, which were confirmed by biophysical, biochemical, and in vivo animal studies. The results demonstrate a high potential of plant expression systems in producing Hb products for use as blood substitutes.

Identification and functional characterization of AP-2 complex subunit mu-A as a new member of antimicrobial protein

AP-2 complex subunit mu-A (AP2M1A) is a component of the adaptor complexes that link clathrin to receptors in coated vesicles. It has recently been shown to be involved in the resistance to oxidative damage, challenging the conventional role of AP2M1A. Here we demonstrated that AP2M1A was a heparin-binding protein abundantly stored in eggs and embryos of zebrafish, and its gene expression was markedly up-regulated by LPS and LTA treatment. We also showed that recombinant AP2M1A (rAP2M1A) was not only able to interact with Gram-negative and Gram-positive bacteria as well as their signature molecules LPS and LTA, but also able to inhibit the growth of the bacteria. Additionally, we found that AP2M1A354-382 that contained 2 closely positioned heparin-binding motifs could also bind to LPS and LTA, and inhibit the bacterial growth. Both rAP2M1A and AP2M1A354-382 were shown to execute antibacterial activity by a combined action of destabilization/destruction of bacterial cell wall through interaction with LPS and LTA, disturbance of the usually polarized membrane through depolarization, and apoptosis/necrosis through intracellular ROS production. Finally, we showed that AP2M1A could protect zebrafish developing embryos/larvae against attack by the potential pathogen Aeromonas hydrophila. All these demonstrate for the first time that AP2M1A is a maternal antimicrobial protein previously uncharacterized. It also establishes a correlation between antibacterial activity and heparin-binding motifs.

Molecular characterization and biological effect of a C-type lectin receptor in Qihe crucian carp, Carassius auratus

C-type lectin receptors, as the important members of pattern-recognition receptors, play the crucial roles in the innate immune system, which discriminate self and non-self by recognizing and binding the carbohydrates on the surface of microorganism. In this study, we identified a C-type lectin receptor gene in Qihe crucian carp Carassius auratus (named as CaCLR). The full-length cDNA of CaCLR was composed of 1130 bp, with a 226 bp 5'-untranslated region (UTR), a 792 bp ORF encoding a 263aa protein, and a 112 bp 3'-UTR with a polyadenylation signal sequence AATAAA and a poly (A) tail. The predicted amino acid sequence of CaCLR is a single transmembrane receptor with a typical carbohydrate recognition domain (CRD) at its C-terminus. With regard to the mRNA transcript of CaCLR, it was ubiquitously detected in the tested tissues, among which it was the most abundant in head kidney. The temporal expressions of CaCLR were obviously up-regulated in liver, spleen, kidney, and head kidney after Aeromonas hydrophila and poly I: C challenge, respectively, and the patterns of expression changes were in a time-depended manner. The recombinant CaCLR (rCaCLR) purified from Escherichia coli BL21 (DE3), exhibited strong binding ability with lipopolysaccharide (LPS), peptidoglycan (PGN), β-Glucan, and Mannan, as well as five microorganisms including fungus (Saccharomyces cerevisiae), Gram-negative bacteria (A. hydrophila, E. coli and Vibrio anguillarum), and Gram-positive bacteria (Micrococcus lysodeikticus). In the presence of rCaCLR, the eliminating capacity against A. hydrophila could be enhanced in C. auratus. Taken together, CaCLR is involved in the antibacterial defense in C. auratus.

Soluble Expression and Efficient Purification of Recombinant Class I Hydrophobin DewA

Hydrophobins are small proteins (<20 kDa) with an amphipathic tertiary structure that are secreted by various filamentous fungi. Their amphipathic properties provide surfactant-like activity, leading to the formation of robust amphipathic layers at hydrophilic–hydrophobic interfaces, which make them useful for a wide variety of industrial fields spanning protein immobilization to surface functionalization. However, the industrial use of recombinant hydrophobins has been hampered due to low yield from inclusion bodies owing to the complicated process, including an auxiliary refolding step. Herein, we report the soluble expression of a recombinant class I hydrophobin DewA originating from Aspergillus nidulans, and its efficient purification from recombinant Escherichia coli. Soluble expression of the recombinant hydrophobin DewA was achieved by a tagging strategy using a systematically designed expression tag (ramp tag) that was fused to the N-terminus of DewA lacking the innate signal sequence. Highly expressed recombinant hydrophobin DewA in a soluble form was efficiently purified by a modified aqueous two-phase separation technique using isopropyl alcohol. Our approach for expression and purification of the recombinant hydrophobin DewA in E. coli shed light on the industrial production of hydrophobins from prokaryotic hosts.

Molecular insights into the endoperoxide formation by Fe(II)/α-KG-dependent oxygenase NvfI

Endoperoxide-containing natural products are a group of compounds with structurally unique cyclized peroxide moieties. Although numerous endoperoxide-containing compounds have been isolated, the biosynthesis of the endoperoxides remains unclear. NvfI from Aspergillus novofumigatus IBT 16806 is an endoperoxidase that catalyzes the formation of fumigatonoid A in the biosynthesis of novofumigatonin. Here, we describe our structural and functional analyses of NvfI. The structural elucidation and mutagenesis studies indicate that NvfI does not utilize a tyrosyl radical in the reaction, in contrast to other characterized endoperoxidases. Further, the crystallographic analysis reveals significant conformational changes of two loops upon substrate binding, which suggests a dynamic movement of active site during the catalytic cycle. As a result, NvfI installs three oxygen atoms onto a substrate in a single enzyme turnover. Based on these results, we propose a mechanism for the NvfI-catalyzed, unique endoperoxide formation reaction to produce fumigatonoid A.

Characterization of a Stable Form of Carboxypeptidase G2 (Glucarpidase), a Potential Biobetter Variant, From Acinetobacter sp. 263903-1

Carboxypeptidase G2 (CPG2) is a bacterial enzyme widely used to detoxify methotrexate (MTX) and in enzyme/prodrug therapy for cancer treatment. However, several drawbacks, such as instability, have limited its efficiency. Herein, we have evaluated the properties of a putative CPG2 from Acinetobacter sp. 263903-1 (AcCPG2). AcCPG2 is compared with a CPG2 derived from Pseudomonas sp. strain RS-16 (PsCPG2), available as an FDA-approved medication called glucarpidase. After modeling AcCPG2 using the I-TASSER program, the refined model was validated by PROCHECK, VERIFY 3D and according to the Z score of the model. Using computational analyses, AcCPG2 displayed higher thermodynamic stability and a lower aggregation propensity than PsCPG2. AcCPG2 showed an optimum pH of 7.5 against MTX and was stable over a pH range of 5-10. AcCPG2 exhibited optimum activity at 50 °C and higher thermal stability at a temperature range of 20-70 °C compared to PsCPG2. The K_m value of the purified AcCPG2 toward folate and MTX was 31.36 µM and 44.99 µM, respectively. The V_max value of AcCPG2 for folate and MTX was 125.80 µmol/min/mg and 48.90  µmol/min/mg, respectively. Accordingly, thermostability and pH versatility makes AcCPG2 a potential biobetter variant for therapeutic applications.

Co-factor-free aggregation of tau into seeding-competent RNA-sequestering amyloid fibrils

Pathological aggregation of the protein tau into insoluble aggregates is a hallmark of neurodegenerative diseases. The emergence of disease-specific tau aggregate structures termed tau strains, however, remains elusive. Here we show that full-length tau protein can be aggregated in the absence of co-factors into seeding-competent amyloid fibrils that sequester RNA. Using a combination of solid-state NMR spectroscopy and biochemical experiments we demonstrate that the co-factor-free amyloid fibrils of tau have a rigid core that is similar in size and location to the rigid core of tau fibrils purified from the brain of patients with corticobasal degeneration. In addition, we demonstrate that the N-terminal 30 residues of tau are immobilized during fibril formation, in agreement with the presence of an N-terminal epitope that is specifically detected by antibodies in pathological tau. Experiments in vitro and in biosensor cells further established that co-factor-free tau fibrils efficiently seed tau aggregation, while binding studies with different RNAs show that the co-factor-free tau fibrils strongly sequester RNA. Taken together the study provides a critical advance to reveal the molecular factors that guide aggregation towards disease-specific tau strains.

Optimization of Multiparameters for Increased Yields of Cytochrome B5 in Bioreactors

The production of recombinant proteins is gaining increasing importance as the market requests high quality proteins for several applications. However, several process parameters affect both the growth of cells and product yields. This study uses high throughput systems and statistical methods to assess the influence of fermentation conditions in lab-scale bioreactors. Using this methodology, it was possible to find the best conditions to produce cytochrome b5 with recombinant cells of Escherichia coli. Using partial least squares, the height-to-diameter ratio of the bioreactor, aeration rate, and PID controller parameters were found to contribute significantly to the final biomass and cytochrome concentrations. Hence, we could use this information to fine-tune the process parameters, which increased cytochrome production and yield several-fold. Using aeration of 1 vvm, a bioreactor with a height-to-ratio of 2.4 and tuned PID parameters, a production of 72.72 mg/L of cytochrome b5 in the culture media, and a maximum of product to biomass yield of 24.97 mg/g could be achieved.

cAMP Biosensor Assay Using BacMam Expression System: Studying the Downstream Signaling of LH/hCG Receptor Activation

Cyclic adenosine monophosphate (cAMP) serves as a second messenger for numerous G-protein-coupled receptors. Changes in cellular cAMP levels reflect the biological activity of various GPCR-specific agents, including protein hormones. cAMP biosensors based on detection of Förster-type resonance energy transfer (FRET) offer unique advantages including the ratiometric nature of measurement, adjustable affinity toward detected molecule, capability of monitoring kinetics of cAMP release, and compatibility with the multi-well format and fluorescence plate reader platforms. In this chapter, we introduce the optimized version of the previously reported method to achieve sufficient and reproducible level of cAMP biosensor protein expression with the means of BacMam transduction system. As a practical challenge, we address the applicability of the designed assay for screening of biological activity of human hormones, including human chorionic gonadotropin (hCG) bearing different posttranslational modifications.

Chaperone-like protein DAY plays critical roles in photomorphogenesis

Photomorphogenesis, light-mediated development, is an essential feature of all terrestrial plants. While chloroplast development and brassinosteroid (BR) signaling are known players in photomorphogenesis, proteins that regulate both pathways have yet to be identified. Here we report that DE-ETIOLATION IN THE DARK AND YELLOWING IN THE LIGHT (DAY), a membrane protein containing DnaJ-like domain, plays a dual-role in photomorphogenesis by stabilizing the BR receptor, BRI1, as well as a key enzyme in chlorophyll biosynthesis, POR. DAY localizes to both the endomembrane and chloroplasts via its first transmembrane domain and chloroplast transit peptide, respectively, and interacts with BRI1 and POR in their respective subcellular compartments. Using genetic analysis, we show that DAY acts independently on BR signaling and chlorophyll biogenesis. Collectively, this work uncovers DAY as a factor that simultaneously regulates BR signaling and chloroplast development, revealing a key regulator of photomorphogenesis that acts across cell compartments.