携带新城疫病毒融合蛋白基因的重组减毒单核细胞增多性李斯特菌构建与鉴定

以鸡新城疫病毒F基因(NDV-F)为模式外源基因,通过基因切割-重叠延伸PCR法(SOE-PCR)将其插入到单核细胞增多性李斯特菌(Listeria monocytogenes)毒力基因hly的启动子和信号肽序列下游,并将该融合片段克隆入穿梭质粒pKSV7,随后将重组质粒电转李斯特菌进行同源重组。NDV-F基因的PCR扩增表明该重组菌构建成功,RT-PCR结果表明F基因在重组菌中得到了转录。比较了重组菌和野生型菌株的溶血性、黏附和侵袭力、对小鼠和鸡胚的毒力和生长特性以及重组菌的体内外稳定性,结果表明:hly基因中F片段的整合消除了单核细胞增多性李斯特菌溶血素基因的表达,其培养上清液没有溶血性,而野生型菌株的溶血价达24;细胞试验表明重组菌对细胞的黏附力和相对侵袭力均有不同程度的降低,而相对侵袭力与野生型菌株具有显著性差异(P<0.05);重组菌对小鼠及鸡胚的毒力(LD50)与野生型相比分别下降3.7和6.5个对数数量级;重组菌在BHI肉汤和小鼠体内连续5次后,仍然可以扩增出目的基因NDV-F,初步表明该重组菌较为稳定。     

Production of recombinant polyhedra containing Cry1Ac fusion protein in insect cell lines

Insect cell lines and the control of infection for obtaining the maximum amount of polyhedrin-CrylAc-polyhedrin fusion protein from Bactrus in monolayer and suspension culture systems were tested. Growth rates of the Trichoplusia ni (High-Five) cell line in both culture systems were better than the other insect cell lines, Spodoptera fiugiferda (Sf-9, Sf-21), Trichoplusia ni (Tn5), and Spodoptera exigua (Se301). The expression of the fusion protein in a monolayer culture showed that Se301 cells were 2.3-4.8 times more productive on a per cell basis than the other cell lines. However, in suspension culture, only High-Five cells were productive. High-Five cells infected with Bactrus at a multiplicity of infection (MOI) of 5 and a cell density of 3.0 x 10(5) cells per ml were more productive than the other infection condition in a suspension culture suitable for a large-scale production of baculovirus. In conclusion, for the large-scale production of Bactrus in vitro, High-Five cells showing good growth and high productivity are suitable.     

Affinity purification of insoluble recombinant fusion proteins containing glutathione-S-transferase

Prokaryotic expression of polypeptides as fusion proteins with glutathione-S-transferase has recently been reported as a one-step means of purifying recombinant protein. The usefulness of the glutathione-S-transferase/glutathioneagarose system, however, is significantly limited by the frequent synthesis of recombinant proteins in insuluble form by Escherichia coli. We have found that for 5 separate fusion proteins containing glutathione-S-transferase and different domains of the large cystic fibrosis transmembrane conductance regulator, all were packaged in insoluble form by E. coli. Insolubility of these products made them inaccessible to one-step purification utilizing this scheme requires proper folding of recombinant glutathione-S-transferase to allow recognition on glutathione affinity agarose, we investigated the suitability of several alternative approaches for converting insoluble recombinant fusion proteins to a soluble form amenable to glutathione-agarose affinity purification. Low-temperature induction of fusion protein synthesis, but not incubation with anion-exchange resins, led to improved one-step purification of glutathione-S-transferase fusion proteins from E. coli cell lysate using mild, nondenaturing conditions. Solubilization in 8 mol/L urea, but not with other chaotropic agents or detergents, also allowed preparative yields of affinity-purified fusion protein. These techniques increase the usefulness of this recombinant protein purification scheme, and should be broadly applicable to diverse polypeptides synthesized as fusions with glutathione-S-transferase.     

层析辅助体外复性含有多对二硫键的融合蛋白质

为建立一种基于阴离子交换介质辅助的含多对二硫键的抗凝溶栓双功能水蛭素12肽-瑞替普酶融合蛋白质 (HV12p-rPA) 的复性方法,采用Q Sepharose XL作为层析复性介质,通过正交实验考察蛋白质上样量、流速、脲梯度、洗脱液中精氨酸浓度、脲浓度、pH、还原型及氧化型谷胱甘肽等因素对复性过程的影响,探索最佳层析复性条件。结果表明：脲梯度、上样量及精氨酸浓度是影响复性的3个主要因素。脲梯度是复性成功的关键,上样量增大时复性蛋白质比活降低,精氨酸辅助HV12p-rPA复性的最佳浓度为1 mol/L。创建了脲、pH双梯度下的阴离子交换层析辅助HV12p-rPA的复性方法,复性后蛋白质的溶栓比活达到46 520 IU/mg,抗凝比活达到9 980 ATU/mg,与稀释复性方法相比,该方法能使复性蛋白质的溶栓比活提高14~15倍,抗凝比活提高7~8倍。     

Self-cleaving fusion tags for recombinant protein production

Fusion expression is a common practice for recombinant protein production. Some fusion tags confer solubility on the target protein whereas others provide affinity handles that facilitate purification. However, the tag usually needs to be removed from the final product, which involves using expensive proteases or hazardous chemicals and requires additional chromatography steps. Self-cleaving tags are a special group of fusion tags that possess inducible proteolytic activity. Combined with appropriate affinity tags, they enable fusion purification, cleavage and target separation to be achieved in a single step, which saves time, labor and cost. This paper reviews currently available self-cleaving fusion tags for recombinant protein production. For each system, an introduction of its key characteristics and a brief discussion of its advantages and disadvantages is given.     

Prokaryotic expression and action mechanism of antimicrobial LsGRP1C recombinant protein containing a fusion partner of small ubiquitin-like modifier

Applied Microbiology and Biotechnology - Antimicrobial peptides (AMPs) are peptides exhibiting broad-spectrum antimicrobial activities and considered as potential therapeutic agents. LsGRP1C, a...     

The pharmacology study of a new recombinant TNF receptor-hyFc fusion protein

TNF-α-blocking agents such as infliximab, adalimumab and etanercept are widely used for the treatment of severe inflammatory diseases including rheumatoid arthritis and psoriasis. The currently used TNF-α blockers have Fc regions of the human IgG1 subtype, which is advantageous in terms of in vivo half-life but also raise the potential for unwanted effector-mediated effects, such as antibody dependent cellular cytotoxicity (ADCC) or complement-dependent cytotoxicity (CDC). To address this issue, we constructed a novel hybrid protein by fusing the TNF receptor (TNFR) with a hybrid Fc (hyFc) consisting of the CH2 and CH3 regions of IgG4 and the highly flexible hinge regions of IgD which would not have ADCC and CDC activity. The resulting fusion protein, TNFR-hyFc, was over-expressed in CHO and pharmacological characteristics were evaluated in comparison with the structurally similar etanercept. TNFR-hyFc effectively neutralized TNF-α in L929 bioassay and showed a 1.5-fold higher neutralizing activity compared to etanercept. In a pharmacokinetic study in cynomolgus monkeys, TNFR-hyFc showed plasma half-life and AUC comparable to etanercept. In a mouse collagen induced arthritis model, TNFR-hyFc showed significant amelioration of arthritis compared to etanercept or vehicle control. In an LPS-induced septic shock model, TNFR-hyFc showed a similar level of protection against mortality as etanercept. These results confirm the feasibility of the TNFR-hyFc as an effective TNF-α blocker for the treatment of inflammatory diseases.     

High-level expression of recombinant human FK-binding protein from a fusion precursor

The human peptidyl-prolyl isomerase FK-binding protein (FKBP) was cloned as a fusion partner with CMP-KDO synthetase (CKS), and the resultant construct was characterized as an improved high-expression source for FKBP. The CKS-FKBP fusion was expressed as a soluble protein at levels approaching 1 gm/L inEscherichia coli fermentations. The fusion protein was purified to near homogeneity by a one-step ammonium sulfate fractionation of whole cell lysate. After selective cleavage, the fusion precursor produced yields approaching 300 mg of purified FKBP per liter of harvested culture, a 30 to 60-fold increase over that observed for a nonfusion construct. Selective cleavage of the fusion partners was accomplished using either hydroxylamine or specific, limited proteolysis. Once separated from the CKS fusion partner, the FKBP was isolated in a single step by either reversed-phase HPLC or chromatography on Q-Sepharose. For comparison of physical and chemical properties, a nonfusion construct of recombinant human FKBP was expressed inE. coli and isolated. The purified FKBPs exhibited expected SDS-PAGE molecular weights and N-terminal sequences. The proteins had similar proton NMR spectra and binding to [³H]FK-506. The fusion construct, CKS-FKBP, was also found to bind [³H]FK-506. These data indicate that FKBP fused to the C-terminus of CKS folds independently of the fusion partner and suggests the fused FKBP adopts a conformation resembling that of the native protein.     

TLR5-dependent immunogenicity of a recombinant fusion protein containing an immunodominant epitope of malarial circumsporozoite protein and the FliC flagellin of Salmonella Typhimurium

Recently, we described the improved immunogenicity of new malaria vaccine candidates based on the expression of fusion proteins containing immunodominant epitopes of merozoites and Salmonella enterica serovar Typhimurium flagellin (FliC) protein as an innate immune agonist. Here, we tested whether a similar strategy, based on an immunodominant B-cell epitope from malaria sporozoites, could also generate immunogenic fusion polypeptides. A recombinant His6-tagged FliC protein containing the C-terminal repeat regions of the VK210 variant of Plasmodium vivax circumsporozoite (CS) protein was constructed. This recombinant protein was successfully expressed in Escherichia coli as soluble protein and was purified by affinity to Ni-agarose beads followed by ion exchange chromatography. A monoclonal antibody specific for the CS protein of P. vivax sporozoites (VK210) was able to recognise the purified protein. C57BL/6 mice subcutaneously immunised with the recombinant fusion protein in the absence of any conventional adjuvant developed protein-specific systemic antibody responses. However, in mice genetically deficient in expression of TLR5, this immune response was extremely low. These results extend our previous observations concerning the immunogenicity of these recombinant fusion proteins and provide evidence that the main mechanism responsible for this immune activation involves interactions with TLR5, which has not previously been demonstrated for any recombinant FliC fusion protein.     

A recombinant single-chain antibody interleukin-2 fusion protein

Recombinant interleukin-2 (rIL-2) therapy has been shown to be of value in the treatment of some cases of melanoma and renal cell carcinoma. However, its use can be limited by severe systemic toxicity. Targeting rIL-2 to the tumor should improve the antitumor immune response and decrease the systemic toxicity. With this aim, we have employed recombinant DNA techniques to construct a single-chain antibody interleukin-2 fusion protein (SCA-IL-2). The protein used in this model system consists of the variable domains of the antilysozyme antibody D1.3 fused to human IL-2 and is expressed inE. coli. It retains antigen-binding specificity and has the full biological activity of rIL-2. This approach can be taken to generate SCA-IL-2 proteins that bind to appropriate cellular antigens. In vivo administration of tumor-binding SCA-IL-2 should result in a localized high concentration of rIL-2 in the tumor tissues, maximizing the antitumor response while keeping systemic side effects to a minimum.     

Improvement of thermostability of recombinant collagen-like protein by incorporating a foldon sequence

Collagen is a popular biomaterial in many specific biological interactions as well as a structural element. In this work, the recombinant collagen-like proteins were synthesized using Escherichia coli expression system. A foldon sequence, GYIPEAPRDGQAYVRKDGEWVLLSTFL, derived from the native T4 phage fibritin was incorporated at the C-terminal of collagen-like protein molecules to stabilize the triple helix formed in the proteins. The differential scanning calorimetry and thermogravimetric analysis measurements showed that the thermostability of the recombinant collagen-like proteins was significantly improved when compared with those without the foldon sequence at the C-terminal. Fourier transform infrared and scanning electron microscopy observations indicated that the collagen-like proteins forms the triple helix structure and prefer to aggregate as fibrils, same as the native collagen. Moreover, the mice fibroblasts L929 cells could attach and grew very well on the recombinant collage-like proteins. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed that the cell biocompatibility of collagen-like proteins produced in this work was even better than that of native collagen, suggesting that the collagen-like proteins may be a satisfactory candidate for the future applications as a biomaterial.     

Role of sequence and structure of the hendra fusion protein fusion Peptide in membrane fusion

Viral fusion proteins are intriguing molecular machines that undergo drastic conformational changes to facilitate virus-cell membrane fusion. During fusion a hydrophobic region of the protein, termed the fusion peptide (FP), is inserted into the target host cell membrane, with subsequent conformational changes culminating in membrane merger. Class I fusion proteins contain FPs between 20 and 30 amino acids in length that are highly conserved within viral families but not between. To examine the sequence dependence of the Hendra virus (HeV) fusion (F) protein FP, the first eight amino acids were mutated first as double, then single, alanine mutants. Mutation of highly conserved glycine residues resulted in inefficient F protein expression and processing, whereas substitution of valine residues resulted in hypofusogenic F proteins despite wild-type surface expression levels. Synthetic peptides corresponding to a portion of the HeV F FP were shown to adopt an α-helical secondary structure in dodecylphosphocholine micelles and small unilamellar vesicles using circular dichroism spectroscopy. Interestingly, peptides containing point mutations that promote lower levels of cell-cell fusion within the context of the whole F protein were less α-helical and induced less membrane disorder in model membranes. These data represent the first extensive structure-function relationship of any paramyxovirus FP and demonstrate that the HeV F FP and potentially other paramyxovirus FPs likely require an α-helical structure for efficient membrane disordering and fusion.     

Combined effect of protein fusion and signal sequence greatly enhances the production of recombinant human GM-CSF in Escherichia coli

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a hematopoietic growth factor, that has been used as a therapeutic agent in facilitating bone marrow and stem cell transplantation and in other clinical cases like neutropenia. Although biologically active recombinant GM-CSF has been successfully produced in Escherichia coli, the reported levels are extremely poor. In this study we looked into the possible reasons for poor expression and found that protein toxicity coupled with protease-based degradation was the principal reason for low productivity. To overcome this problem we attached a signal sequence, as well as an amino-terminal His-tag fusion to the GM-CSF gene. This combination had a dramatic effect on expression levels, which increased from 0.8 microg/mL in the control to 40 microg/mL. When a larger fusion partner, such as the Maltose-binding protein (MBP-tag), was used the expression levels increased further to 69.5 microg/mL, which along with the MBP-tag represented approx 12% of the total cellular protein.     

Ultra-high expression of a thermally responsive recombinant fusion protein in E. coli

Elastin-like polypeptides (ELPs) are recombinant peptide-based biopolymers that contain repetitive sequences enriched in glycine, valine, proline, and alanine. Because of the unusually large fraction of these amino acids in ELPs as compared to other cellular proteins, we hypothesized that intracellular pools of these amino acids can be selectively depleted and limit protein yields during expression. In this study, we examined how culture conditions and individual medium components affect protein yields by monitoring cell growth and protein expression kinetics of E. coli expressing an ELP tagged with a green fluorescent protein (GFP). By determining the underlying principles of superior fusion protein yields generated by the hyperexpression protocol, we further improved protein yields through the addition of glycerol and certain amino acids such as proline and alanine and found that amino acid concentrations and the type of basal medium used strongly influenced this beneficial effect. Surprisingly, amino acids other than those that are abundant in ELPs, for example, asparagine, aspartic acid, glutamine, and glutamic acid, also enhanced protein yields even in a nutrient-rich medium. Compared to commonly used Luria-Bertani medium, the protein yield was improved by 36-fold to the remarkable level of 1.6 g/L in shaker flask cultures with a modified medium and optimized culture conditions, which also led to a 8-fold reduction in the cost of the fusion protein. To our knowledge, this is the highest yield of an ELP-fusion protein purified from E. coli cultured in shaker flasks. This study also suggests a useful strategy to improve the yields of other ELP fusion proteins and repetitive polypeptides.     

Combined effect of protein fusion and signal sequence greatly enhances the production of recombinant human GM-CSF in Escherichia coli

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a hematopoietic growth factor, that has been used as a therapeutic agent in facilitating bone marrow and stem cell transplantation and in other clinical cases like neutropenia. Although biologically active recombinant GM-CSF has been successfully produced in Escherichia coli, the reported levels are extremely poor. In this study we looked into the possible reasons for poor expression and found that protein toxicity coupled with protease-based degradation was the principal reason for low productivity. To overcome this problem we attached a signal sequence, as well as an amino-terminal His-tag fusion to the GM-CSF gene. This combination had a dramatic effect on expression levels, which increased from 0.8 μg/mL in the control to 40 μg/mL. When a larger fusion partner, such as the Maltose-binding protein (MBP-tag), was used the expression levels increased further to 69.5 μg/mL, which along with the MBP-tag represented approx 12% of the total cellular protein.     

一种真核细胞分泌型重组融合蛋白rPC的构建、表达与纯化

抑制性免疫检查点PD-1或CTLA-4靶向治疗药物已用于肿瘤的临床治疗,但单一靶点药物会有耐药发生,联合使用同时封闭多个靶点可提高疗效,因此拟构建一个可封闭多个靶点的新型重组蛋白。首先设计并合成了一个由人类PD-1和CTLA-4两个受体的胞外功能域组成并且C端带6×His标签的分泌型重组融合蛋白rPC编码序列,插入真核细胞表达载体pLVX-IRES-ZsGreen1,稳定转染HEK293细胞,收集细胞培养上清,以亲和方法纯化重组蛋白rPC,通过实时荧光定量PCR检测多个人类肿瘤细胞系中PD-1配体PD-L1、PD-L2和CTLA-4配体CD80、CD86的表达,以选择相对高表达的细胞,利用细胞免疫荧光染色方法检验rPC与肿瘤细胞的结合能力,并用CCK-8法检测rPC是否对肿瘤细胞的生长有影响。结果表明,重组融合蛋白rPC可由稳定转染表达载体的HEK293细胞表达并分泌,纯化后的rPC可以与PD-1和CTLA-4配体表达相对较高的肺癌细胞NCI-H226结合,并且rPC处理对其生长并无直接影响,与预期一致。成功获得的重组融合蛋白rPC可用于进一步的体内外功能研究,也为今后研发新型多靶点肿...     

Identification of a short rDNA spacer sequence highly specific of a tomato line containing Tm-1 gene introgressed from Lycopersicon hirsutum

Summary We studied rDNA restriction fragment length polymorphism between two tomato lines used for F₁ hybrid seed production: line A, containing the Tm-1 gene responsible for tobacco mosaic virus tolerance introgressed from the wild species Lycopersicon hirsutum, and line B, a tobacco mosaic virus sensitive line. Hybridization patterns led to distinct rDNA maps with two size classes, 10.4 and 10.7 kb, in line A and a single, 8.9-kb class in line B. Size differences were located in the intergenie sequence (IGS). A highly specific 54-bp TaqI fragment was cloned from the line A IGS and used in dot blot experiments to probe total DNA from line A, line B, and their F₁ hybrid. It proved capable of discriminating B from A and the hybrid. This probe could thus serve to screen inbreds in commercial seed lots where line A is used as male. This fragment showed 80–90% sequence homology with the 53-bp subrepeats previously characterized in a region of the tomato IGS close to the 25S rRNA gene. Preliminary comparison of rDNA in line A and several wild related species indicated that the L. hirsutum H₂ genotype was the closest to line A. rDNA variations between line A and this wild genotype could be explained by recombination during the introgression process involving numerous backcrosses or by an important intraspecific polymorphism. Our results strongly suggest that Tm-1 and the rDNA were introgressed together into tomato from L. hirsutum through linkage drag.     

Correction to: Prokaryotic expression and action mechanism of antimicrobial LsGRP1C recombinant protein containing a fusion partner of small ubiquitin-like modifier

Applied Microbiology and Biotechnology - The published online version contains editing mistake in Table 2. See below for the corrected Table.     

Production of recombinant oxytocin through sulfitolysis of inteincontaining fusion protein

An artificial gene consisting of seven copies of an oxytocinoyl-lysine encoding sequence arranged in a tandem was synthesized and inserted downstream of the SspDnaB intein gene in a pTWIN1 plasmid. The corresponding fusion protein Dnab-7oxy contained 16 cysteine residues and formed inclusion bodies when expressed in E. coli. The standard protocol involving solubilization of the fusion protein and its autocatalytic cleavage on a chitin resin was not effective because of a very low yield of the cleavage reaction. Attempts to perform a refolding of the intein part of the fusion protein in solution were also unsuccessful because of a high level of protein aggregation. Sulfitolysis of cysteine residues is known to increase a solubility of proteins and peptides. Therefore we suggested a one-step approach that combines solubilization of inclusion bodies and sulfitolysis of a hybrid protein. The fusion protein was completely reduced and solubilized in 8M urea at pH 9.0 in the presence of sodium sulfite and sodium tetrathionate. The sulfitized protein was loaded onto a chitin column, an efficient cleavage was induced by a pH shift from 9.0 to 6.5, and seven successively connected oxytocinoyl- lysine units were released. The heptamer was subjected to trypsinolysis yielding sulfitized monomers of oxytocinoyllysine. Oxytocinoyl-lysine was refolded as described previously and treated by carboxypeptidase B to form the oxytocinic acid. The target oxytocin amide was then synthesized via methyl ester intermediate. Using this approach 6 mg of recombinant oxytocin can be obtained from 1 g of biomass.