Cloning,co-expression with an amidating enzyme,and activity of the scorpion toxin BmK ITa1 cDNA in insect cells

BmK ITa1 is an insect-specific neurotoxin from the Chinese scorpion Buthus martensi Karsch (Bmk). We succeeded in obtaining biologically active recombinant BmK ITa1 protein by simultaneous expression in insect cells of BmK ITa1 cDNA with an amidating enzyme expressed by the rat peptidylglycine α-amidating monooxygenase (PAM) gene. We investigated the insecticidal efficacy of recombinant BmK ITa1/W (without coexpression of PAM), and of BmK ITa1/A (with coexpression of PAM) in 5th instar Bombyx mori, by injecting these recombinant toxins into larvae. The lethal time for 50% of larvae (LT₅₀) was 9 h for BmK ITa1/A and 17 h for BmK ITa1/W. At 19 h after injection all of the larvae exposed to BmK ITa1/A had been killed, whereas only half of the larvae exposed to BmK ITa1/W had been killed. These results show that the simultaneous expression of an amidating enzyme can result in apparently higher insecticidal activity of BmK ITa1.     

Purification of two depressant insect neurotoxins and their gene cloning from the scorpion Buthus martensi Karsch.

Insect-specific neurotoxins are important components of scorpion venoms. In this study, two toxins from the scorpion Buthus martensi Karsch (BmK) were purified. They shared high sequence homology with other depressant insect toxins and were designated BmK ITa and BmK ITb, respectively. They were able to suppress the action potential of cockroach isolated axon, which is due to a decrease in the peak sodium current. Furthermore, the effect of BmK ITb was lower than that of BmK ITa, and some of the electrophysiological characteristics of BmK ITb even resemble that of excitatory insect toxins. Their primary structures were determined by N-terminal partial sequence determination and cDNA cloning. The differences in their structures, especially the 31st residues, may result in the unique activity of BmK ITb.     

Intein介导的重组昆虫毒素BmK IT在大肠杆菌中的可溶性表达、纯化及活性分析

为获得重组蝎昆虫毒素BmKIT,通过PCR方法在BmKIT基因的3′端融合了编码6个组氨酸残基的核苷酸序列,将其插入原核表达载体pTWIN1的内含肽Ssp DnaB Intein基因下游的多克隆位点(MCS)。将获得的表达质粒转化大肠杆菌BL21(DE3)中,用IPTG诱导融合蛋白表达。用Ni-NTA亲和层析柱从菌体裂解液中纯化了CBD-Intein-BmK IThis6融合蛋白,并在柱上诱导Intein自剪切,成功去除融合子CBD-Intein。通过Superdex75凝胶过滤层析获得了纯度达95%以上的BmK IThis6蛋白,该蛋白不仅具有正确的二级结构而且有生物活性。     

Expression and purification of the BmK Mm2 neurotoxin from the scorpion Buthus martensii Karsch and its biological activity test

The gene encoding neurotoxin (BmK Mm2) from the scorpion Buthus martensii Karsch was expressed in Escherichia coli BL21 (DE3) at a level of 1.6 mg/L using expression plasmid pExSecI system. SDS-PAGE analysis of the cell lysate confirmed that gene BmK Mm2 was expressed in soluble form and the expressed production was secreted into Luria-Bertani (LB) culture medium from Escherichia coli. According to the characters of pExSecI expression system, the IgG binding domain-ZZ of Protein A is fused to the N-terminal of BmK Mm2. Recombinant BmK Mm2 (ZZ-BmK Mm2, pI 6.81, 22.007 kDa) was purified rapidly and efficiently by IgG-Sepharose 6 Fast Flow and Superdex-75 gel filtration chromatography, produced a single band on SDS-PAGE. Western blot analysis demonstrated that this protein was recombinant BmK Mm2. The results of MTT assay, morphological observation of nucleus and single cell gel electrophoresis showed that the expressed recombinant BmK Mm2 was toxic for glial cells of mice, which indicate that it has biological activity.     

Expression of an Insect Excitatory Toxin, BmK IT, from the Scorpion, Buthus martensii Karsch, and its Biological Activity

An insect excitatory toxin from Buthus martensii Karsch (BmK IT) was cloned into the expression vector, pTWIN1, and expressed into Escherichia coli BL21 (DE3) host cells. The soluble fusion expression of CBD-intein-BmK IT was obtained. The recombinant BmK IT was purified by two anion-exchange chromatography columns and one gel chromatography column. Bioassays were carried out to verify the toxicity of this recombinant toxin. At the end of a 96 h experimental period, 83% of cotton bollworm larvae were killed with an LT(50) value of 58-62 h. Furthermore, the average weight of larvae fed on BmK IT-containing media was approx 4% of that of the control groups. The results indicate that the expressed and purified recombinant BmK IT has biological activity.     

Expression, renaturation and functional analysis of an excitatory insect-specific toxin from scorpion Buthus martensii Karsch

The cDNA of BmK IT-AP, an excitatory insect toxin from the scorpion Buthus martensi Karsch that has an analgesic effect on mammalian cells, was expressed in E. coli in the form of an inclusion body. Following denaturation and reduction, the recombinant protein was renatured and purified by liquid chromatography. The authenticity of the recombinant product was confirmed by bioassay and its electrophysiological effect on insect sodium channel.     

High-level expression and purification of an analgesic peptide from Buthus martensii Karch

BmK AngM1, a scorpion peptide isolated from Buthus martensii Karch was reported to exhibit potential analgesic effect. But the relative low content of this toxin in crude venom limits its further characterization. In this study, we constructed an expression vector and transformed into E.coli. The BmK AngM1 was expressed as a fusion protein in the soluble fraction and was purified by Nickel affinity chromatography. Subsequently, the purified fusion protein was cleaved by enterokinase and was further purified by reverse-phase HPLC. We purified 25 mg recombinant BmK AngM1 (rBmK AngM1) from 1 L bacterial culture. The molecular weight of rBmK AngM1 determined by ESI-MS was 7240.4 Da which was the expected size for correctly processed. Analgesic bioassay studies of rBmK AngM1 exhibited its potential analgesic effect comparable to that of the natural BmK AngM1 peptide.     

丙型肝炎病毒结构蛋白E1在昆虫细胞中的表达及定位

本文在大肠杆菌中表达了与GST融合无跨膜区的丙型肝炎病毒(Hepatitis C Virus,HCV)E1蛋白,并通过免疫兔制备了兔抗E1的抗血清。然后利用Bac-to-Bac杆状病毒表达系统构建了含有HCV结构蛋白E1基因的重组杆状病毒vAcHCVE1。通过Western blot分析,E1蛋白在Sf9细胞中表达分子量大小为30kDa大于预测的20kDa,表明存在翻译后修饰如糖基化等。通过Confocal显微镜观察当感染48h后E1蛋白定位在细胞质和细胞膜上。     

Soluble expression, purification and the role of C-terminal glycine residues in scorpion toxin BmK AGP-SYPU2

The existence of glycine residues in long-chain scorpion toxins has been well documented. However, their role as analgesics has not been evaluated. To address this issue, we investigated the functional role of glycines in the C-terminal end of Chinese-scorpion toxin from Buthus martensii Karsch (BmK AGP-SYPU2) using site-directed mutagenesis and analgesic activity assays. Recombinant BmK AGP-SYPU2 and its mutants were efficiently expressed in E. coli and purified to homogeneity using immobilized metal ion affinity chromatography (IMAC) and cation exchange chromatography. The mouse-twisting test was used to detect the analgesic activity of BmK AGP-SYPU2 and its mutants. As a result, we identified glycines at the C-terminal end that, when altered, significantly affected analgesic activity. Also, Mut6566 was significantly decreased compared to BmK AGP-SYPU2. These data indicate that the glycines at the C-terminal end are important for the analgesic activity of BmK AGP-SYPU2.     

表达蝎毒素的重组斜纹夜蛾核型多角体病毒(SpltMNPV)的构建及毒力

【目的】开发高毒力的重组斜纹夜蛾核型多角体病毒(Spodoptera litura multicapsid nucleopolyhedroviruse,SpltMNPV)杀虫剂。【方法】构建编码蜕皮激素UDP-葡萄糖基转移酶(ecdysterioid UDP-glucosyl transferase gene,egt)基因缺失并插入东亚钳蝎神经毒素(B.martensi Karsch,BmK ITa1)基因的重组转移载体,重组转移载体与SpltMNPVⅡ基因组DNA共转染斜纹夜蛾细胞,通过荧光斑法与有限稀释法相结合筛选重组病毒。【结果】成功筛选出缺失egt基因的、早期启动子(ie-1)启动的、表达BmK ITa1成熟肽的重组病毒SpltMNPV-Δegt-Pph-egfp-ie-1-BmK ITa1。生物测定结果显示,重组病毒的杀虫速度(LT50)较野生病毒提前0.7-0.8 d。【结论】通过在SpltMNPV病毒基因组中插入外源毒素基因可明显增强病毒的杀虫效果,结果说明开发高毒力SpltMNPV生物杀虫剂具有可行性。     

Baculoviral polyhedrin-Bacillus thuringiensis toxin fusion protein: a protein-based bio-insecticide expressed in Escherichia coli

Previously, we found that baculoviral polyhedrin (Polh) used as a fusion partner for recombinant expression in Escherichia coli showed almost the same characteristics (rapid solubilization under alkaline conditions and specific degradation by specific alkaline proteases in insect midgut) as the native baculoviral Polh, and formed easily isolatable inclusion bodies. Here, Polh derived from the Autographa californica nuclear polyhedrosis virus (AcNPV) was fused with a Bacillus thuringiensis (Bt) toxin protein (truncated Cry1Ac having toxin region as a model Bt toxin) for the novel generation of a new bio-insecticide. The Polh-Cry1Ac fusion protein (approximately 99 kDa) was highly expressed (3.6-fold induction as compared to E. coli-derived single Cry1Ac (approximately 68 kDa)) as an insoluble inclusion body fraction in E. coli. Trypsin and alpha-chymotrypsin, which have similar properties to the insect midgut alkaline proteases, rapidly degraded the Polh portion in vitro, leaving only the toxic Cry1Ac protein behind. In vivo, the Polh-Cry1Ac fusion protein showed high insecticidal activity against the pest, Plutella xylostella. Because this novel bio-insecticide employs E. coli as the host, mass production at a low cost should be possible. Also, since this is a protein-based insecticide, living modified organism (LMO) issues such as environmental and ecological safety can be avoided.     

一种东亚钳蝎碱性神经毒素的纯化和初步晶体学研究

经ＳｅｐｈａｄｅｘＧ－５０和ＳＰ－ＳｅｐｈａｄｅｘＣ－２５两次柱层析,从河南淅川马氏钳蝎毒素中分得一种碱性神经毒素ＢｍＫＭＩ８．等电聚焦和ＳＤＳ电泳显示单一组分,其ｐＩ为９．１,Ｍｒ为７１００．毒性测试结果表明,该组分对小白鼠有较强的毒性,对昆虫也有一定的毒性,已获得该毒素的两种晶型的大单晶,并测定其空间群为Ｐ２＿１２＿１２＿１,晶胞参数为：ＢｍＫＭＩ８－Ａ：ａ＝３６．７,ｂ＝２６．６,ｃ＝５２．０,ＢｍＫＭＩ８－Ｂ：ａ＝３６．６４Ａ,ｂ＝３７．３１,ｃ＝３７．９５,已收集了ＢｍＫＭＩ８－Ｂ分辨率为１．７４的Ｘ射线单晶衍射数据。     

东亚钳蝎神经毒素在大肠杆菌中的表达

以山西风陵渡东亚钳蝎（ＢｕｔｈｕｓｍａｒｔｅｎｓｉＫａｒｓｃｈ）的尾腺总ＲＮＡ为模板,根据已知的蝎神经毒素保守氨基酸序列设计引物,利用ＰＣＲ技术,扩增并克隆了两个蝎神经毒素基因．序列分析表明,由两个基因导出的氨基酸序列（ＢｍＫＭｍ１和ＢｍＫＭｍ２）与已知的蝎神经毒素ＢｍＫⅠ、ＢｍＫⅡ、ＢｍＫⅢ、ＢｍＫＭ１、ＢｍＫＭ９有很高的同源性．将ＢｍＫＭｍ２基因重组到大肠杆菌分泌型表达载体ｐＥｘＳｅｃ１中进行表达．ＳＤＳ－ＰＡＧＥ证明表达产物被分泌到细胞周间质及培养液中．经ＩｇＧ－Ｓｅｐｈａｒｏｓｅ纯化后的蛋白质注射小白鼠表明表达产物有生物学活性     

Effect of location of the His-tag on the production of soluble and functional Buthus martensii Karsch insect toxin

The low yield and poor folding efficiency in vivo of soluble and active recombinant cysteine-rich proteins expressed in Escherichia coli are a major challenge for large-scale protein production and purification. Expression vectors containing Buthus martensii Karsch insect toxin (BmK IT) fused to the C terminus of the intein Ssp DnaB were constructed in an attempt to overcome this problem. Following purification and intein self-cleavage, the fusion protein His(6)-intein-IT produced insoluble BmK IT, while intein-IT-His(6) generated soluble and properly folded BmK IT. This result indicated that the positioning of the His(6) tag has a key role in the production of soluble and functional BmK IT.     

猪细小病毒vp2基因的表达和类病毒颗粒的构建

利用PCR方法从病毒基因组中获得了vp2完整的编码区并经测序后克隆到原核表达载体pET-32(a)上。在大肠杆菌中诱导表达了VP2与Trx-His-STag的融合蛋白,通过免疫家兔获得了高特异性的兔抗血清。另外,将vp2克隆到pFastBacDUAL载体上,利用昆虫表达系统,即AcMNPV的Bac-to-Bac系统对vp2进行了表达,经SDS-PAGE和Westernblot分析,表达产物为64kD,并且该蛋白能在昆虫细胞中形成类病毒颗粒。     

水稻巯基蛋白酶抑制剂cDNA在大肠杆菌中的表达

根据从水稻未成熟种子cDNA文库中筛选出的水稻巯基蛋白酶抑制剂(Oryzacys-tatin)cDNA序列,利用聚合酶链反应(PCR)技术扩增出Oryzacystatin编码区,插入到温度敏感型大肠杆菌表达载体的PtPL启动子下游．该质粒带有温度敏感型阻遏子的编码基因cIts857。转化大肠杆菌DH5a后。通过升温诱导,Oryzacystatin在大肠杆菌中获得高教表达,SDS—PAGE表明分子量约为12kDa。与预期结果一致,表达量占细菌可溶性蛋白总量的10％以上,对巯基蛋白酶的抑制活性检测表明,可溶性蛋白组分对木瓜蛋白酶有明显的抑制活力。     

Recombinant scorpion insect excitatory toxin BmK IT accelerates the growth of insect Spodoptera frugiperda 9 cells

Several scorpion insect toxins are selectively active on the lepidopterous and dipterous insects. The gene encoding insect excitatory neurotoxin (BmK IT) from the scorpion Buthus martensii Karsch was expressed in Escherichia coli BL21(DE3) at a high level of 3 mg/0.5 L using the prokaryotic expression system pTWIN1. Colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), whole-cell patch-clamp technique and immunofluorescence assays were used to evaluate the toxicity of rBmK IT to insect Spodoptera frugiperda 9 (Sf9) cells and to analyze the potential mechanism of this toxicity. rBmK IT accelerated the growth of Sf9 cells in a dose-dependent manner. Voltage-gating sodium channel activity could not be detected in Sf9 cells using a whole-cell patch-clamp technique. However, immunofluorescence analysis clearly showed co-localization of tetrodotoxin (TTX) and rBmK IT on the Sf9 cell membrane, which demonstrated that rBmK IT could bind to and act on the voltage-gated sodium channels on the Sf9 cells by the high affinity action power. The findings presented in this study are essential for further study of this peptide.     

马氏钳蝎毒昆虫类神经毒素的分离、纯化及性质研究

经Sephadex G-50,sp-Sephadex C-25二步柱层析法,从山东马氏钳蝎(Bu-thus martensii Karch)粗毒中分离出四种对美洲(虫非)蠊有强直麻痹反应的毒性蛋白组份。其中二个组分在SDS聚丙烯酰胺电泳和等电聚焦电泳上均呈现单一区带,命名为BmK IT-Ⅰ,BmK IT-Ⅱ其pI分别为8.2和8.4,分子量分别为8400和7560。同时还分析了二个组份的氨基酸组成。经DABITC/PITC双偶合法测定了BmKIT-Ⅰ和BmK IT-Ⅱ的N端部份氨基酸排列顺序,它们分别为H_2NVal.Arg.Asp.Ala……H_2NVal.Arg.Asp.Gly……。 电生理学研究表明,纯化的BmK IT-I(1×10~(-5)g/ml)对(虫非)蠊腹Ⅵ神经节的突触传递有阻断作用,阻断后用生理溶液洗,则突触传递可恢复。从同一蝎毒粗毒中分离纯化的哺乳动物类神经毒素BmKⅢ在浓度高出100倍(1×10~(-3)g/ml)时也可以阻断(虫非)蠊腹Ⅵ神经节的突触传递,但用生理溶液冲洗没有观察到恢复。     

Comparison of biological activity of recombinant woodchuck interferon gamma and tumor necrosis factor alpha produced in baculovirus and Escherichia coli expression systems

The full-length cDNAs of recombinant woodchuck interferon gamma (rwIFN gamma) and woodchuck tumor necrosis factor alpha (rwTNF alpha) were cloned into baculovirus transfer vectors and expressed in insect Sf9 cells. The recombinant proteins secreted by the insect cells, bac-rwIFN gamma and bac-rwTNF alpha, were found to be functionally competent. Their biological activities were compared to those of rwIFN gamma and rwTNF alpha produced in the Escherichia coli (E. coli) expression system. The bac-rwIFN gamma demonstrated a 4.5-fold greater protective activity against encephalomyocarditis virus-induced cytolysis of woodchuck hepatocytes and that of class I MHC antigen presentation on the hepatocytes than rwIFN gamma derived from E. coli. The bac-rwTNF alpha was cytotoxic towards murine fibroblasts and able to upregulate class I MHC antigen display and these effects were about 18-fold greater than those triggered by rwTNF alpha from E. coli at a comparable protein level. In addition, the antiviral activity of bac-rwIFN gamma was inhibited by anti-wIFN gamma antibodies and the cytotoxicity of bac-rwTNF alpha neutralized by cross-reactive antibodies to murine TNF alpha. The study showed that the expression of rwIFN gamma and rwTNF alpha in the baculovirus system generated biologically active cytokines whose potency was considerably greater than those produced in E. coli.     

抗黄曲霉毒素B1单链抗体在Sf9昆虫细胞中的表达与性质分析

目的:在原核表达抗黄曲霉毒素B1(aflatoxin B1,AFB1)单链抗体(single chain Fv fragment,scFv)研究的基础上,为进一步了解和提高抗AFB1 scFv的活性,利用Sf9昆虫细胞表达抗AFB1 scFv,并对其活性进行探索研究。方法:构建pFastBac 1-scFv2E6VHVL重组质粒,将重组质粒转化Escherichia coli (E. coli) DH10Bac细胞,进行蓝白斑筛选,挑取阳性克隆。提取相应的重组杆状病毒穿梭载体Bacmid侵染Sf9昆虫细胞,表达scFv,利用镍亲和层析法纯化scFv,并以ELISA检测scFv活性。结果:蓝白斑筛选后,经菌落PCR和测序验证挑取的白斑阳性单克隆含有正确的单链抗体基因。提取相应的重组杆状病毒穿梭载体Bacmid侵染Sf9昆虫细胞,通过Western blot检测得知抗AFB1 scFv在Sf9昆虫细胞中成功表达。AFB1对scFv的抑制中浓度(IC₅₀)为30μg/ml。结论:与E. coli BL21(DE3)表达系统相比,scFv灵敏度转好,但仍有较大提升空间。