Increased levels of recombinant human proteins with the Escherichia coli strain Rosetta(DE3)

The effect of two Escherichia coli expression strains on the production of recombinant human protein fragments was evaluated. High-throughput protein production projects, such as the Swedish Human Protein Atlas project, are dependent on high protein yield and purity. By changing strain from E. coli BL21(DE3) to E. coli Rosetta(DE3) the overall success rate of the protein production has increased dramatically. The Rosetta(DE3) strain compensates for a number of rare codons. Here, we describe how the protein expression of human gene fragments in E. coli strains BL21(DE3) and Rosetta(DE3) was evaluated in two stages. Initially a test set of 68 recombinant proteins that previously had been expressed in BL21(DE3) was retransformed and expressed in Rosetta(DE3). The test set generated very positive results with an improved expression yield and a significantly better purity of the protein product which prompted us to implement the Rosetta(DE3) strain in the high-throughput protein production. Except for analysis of protein yield and purity the sequences were also analyzed regarding number of rare codons and rare codon clusters. The content of rare codons showed to have a significant effect on the protein purity. Based on the results of this study the atlas project permanently changed expression strain to Rosetta(DE3).     

Gas8蛋白的抗体制备及小鼠组织表达图谱分析

目的：制备Gas8抗体,并检测小鼠各组织中Gas8表达谱。方法：在大肠杆菌BL21（DE3）中表达His标签标记的Gas8融合蛋白,以纯化的Gas8重组融合蛋白为抗原制备兔Gas8多抗血清,进一步利用亲和纯化方法制备Gas8多克隆抗体;为确定Gas8抗体的特异性,通过免疫印迹方法检测瞬时表达的Flag-Gas8融合蛋白,同时以抗Flag单克隆抗体作为对照;利用制备的抗体通过Westernblot检测Gas8在小鼠各组织中的表达谱。结果：与Gas8特异性结合的抗体能够通过免疫法获得;利用制备的抗体检测到Gas8在小鼠心、肺、肾、脑、肝、脾、肌肉、睾丸各组织中均表达。结论：获得了特异性抗Gas8抗体,用该抗体可以检测到小鼠组织中Gas8的表达。     

大肠杆菌Ee株SLT-IIeB与FedF基因的融合表达及表达产物的免疫原性研究

根据猪水肿病大肠杆菌Ee株主要免疫原性片段SLT-IIeB和FedF的基因序列,利用PCR技术克隆目的片段,将SLT-IIeB和FedF基因依序串联于谷胱甘肽-S-转移酶(GST)表达系统的GST下游,在大肠杆菌中成功获得了大小约为63kDa融合蛋白GST-SF,Western blot检测证实表达的融合蛋白具有良好的生物学活性。以纯化的融合蛋白为抗原免疫新西兰兔制备血清,体外活性试验表明,所制备的抗血清能中和Ee株水肿毒素对Vero细胞的病变效应;黏附抑制试验证实抗血清能抑制Ee株对猪小肠刷状缘细胞的黏附。将融合蛋白免疫小鼠,结果表明,GST-SF能够诱发较好的免疫反应,并能提供对Ee株5LD50致死剂量的70%保护率。研究表明GST-SF融合蛋白具有良好的免疫原性,具有良好的应用前景。     

Expression and purification of the SsbB protein from Streptococcus pneumoniae

The Gram positive bacterium, Streptococcus pneumoniae, has two genes, designated ssbA and ssbB, which are predicted to encode single-stranded DNA binding proteins (SSB proteins). We have shown previously that the SsbA protein is similar in size and in biochemical properties to the well-characterized SSB protein from Escherichia coli. The SsbB protein, in contrast, is a smaller protein and has no counterpart in E. coli. This report describes the development of an expression system and purification procedure for the SsbB protein. The ssbB gene was amplified from genomic S. pneumoniae DNA and cloned into the E. coli expression vector, pET21a. Although, we had shown previously that the SsbA protein is strongly expressed from pET21a in the E. coli strain BL21(DE3)pLysS, no expression of the SsbB protein was detected in these cells. However, the SsbB protein was strongly expressed from pET21a in the Rosetta(DE3)pLysS strain, a derivative of BL21(DE3)pLysS which supplies the tRNAs for six codons that are used infrequently in E. coli. The differential expression of the two SSB proteins in the parent BL21(DE3)pLysS strain was apparently due to the presence of two rare codons in the ssbB gene sequence that are not present in the ssbA sequence. Using the Rosetta(DE3)pLysS/pETssbB expression system, a protocol was developed in which the SsbB protein was purified to apparent homogeneity. DNA binding assays confirmed that the purified SsbB protein had single-stranded DNA binding activity. The expression and purification procedures reported here will facilitate further investigations into the biological role of the SsbB protein.     

海栖热袍菌极耐高温木聚糖酶基因xynB64在大肠杆菌中的融合表达

来源于极端嗜热菌海栖热袍菌(Thermotoga maritima MSB8)的木聚糖酶B具有极高的热稳定性,在饲料、造纸、能源和食品医药行业具有巨大应用潜力。携带酶基因xynB64的pET28a(+)重组载体在宿主大肠杆菌BL21(DE3)中诱导表达,重组酶活力较低。更换宿主为携带稀有tRNA基因的大肠杆菌:BL21-CodonPlus(DE3)-RIPL和Rosetta(DE3)后,酶活力分别提高了197%和277%,但是后者中的表达会形成部分包涵体。宿主菌为大肠杆菌Rosetta(DE3),更换载体为4种融合表达载体pET32a(+)、pET42a(+)、pET43.1a(+)和pMAL-c2X进行表达,重组酶分别融合了Trx、GST、Nus和MBP标签。其中Rosetta(DE3)/pMAL-c2X-xynB64表达酶活力最高,相当于Rosetta(DE3)/pET28a-xynB64表达酶的88%,而且目的酶表达量占全细胞蛋白的40%,几乎不形成包涵体。     

Development of the system ensuring a high-level expression of hepatitis C virus nonstructural NS5B and NS5A proteins

The plasmid pET-21d-2c-5BDelta55 effectively expressing a C-terminally truncated form (NS5BDelta55) of the hepatitis C virus (HCV) RNA-dependent RNA polymerase (RdRp) was constructed. It was derived from pET-21d-5BDelta55 plasmid and contained six mutations in the ATG-start codon region and an additional cistron upstream the target gene. The C-terminally His-tagged NS5BDelta55 protein was expressed in Rosetta(DE3) Escherichia coli strain bearing an additional pRARE plasmid encoding extra copies of rare tRNAs. The yield of the target enzyme exceeded by a factor of 29 the yield of NS5BDelta55 protein expressed from the parental pET-21d-5BDelta55 plasmid (5 mg/L). The increase in the protein yield could be explained by facilitated protein translation initiation, resulted from disruption of the stable secondary mRNA structure. The pET-21d-2c-5BDelta55 plasmid yielded one third amount of the protein when expressed in BL-21(DE3) strain, indicating that the pRARE plasmid is required for a high-level expression of NS5BDelta55 protein. The 29-fold enhancement of the protein yield was accompanied by only a 2.5-fold increase of the corresponding mRNA level. The expression of another HCV NS5A protein His-tagged at the C-terminus in the developed system yielded a similar amount of the protein (4 mg/L), whereas its N-terminally His-tagged counterpart was obtained in a 30 mg/L yield. The NS5A protein purified under denaturing conditions and renatured in solution inhibited the HCV RdRp and was a substrate for human casein kinase II.     

凋亡素融合蛋白的可溶性表达及活性分析

目的:构建PET-28a-SPA原核表达载体,在大肠杆菌BL21(DE3)中实现其高效可溶性表达,测定对肿瘤细胞的凋亡效果。方法:本实验在获得凋亡蛋白融合基因的基础上,成功地构建了重组表达质粒PET-28a-SPA,将阳性重组质粒转化表达受体菌BL21(DE3)感受态细胞中,经IPTG诱导表达,表达产物经聚丙烯酰胺凝胶电泳检测和Western blot检测,并采用MTT法检测其对肿瘤细胞的增殖抑制。结果:表达产物经聚丙烯酰胺凝胶电泳检测,凋亡蛋白融合基因获得高效表达,软件分析表明表达蛋白占菌体蛋白20%左右。上清表达量约为10%。上清蛋白经纯化后,Western blot结果显示,利用凋亡蛋白单克隆抗体可以很好地和所表达的蛋白带特异性结合,并且对A549肺癌细胞及Hela细胞具有一定的凋亡作用。结论:所获凋亡蛋白以高效胞质可溶形式表达,为其研制有效的肿瘤免疫治疗靶向药物提供一定的基础。     

一种新的螯虾丝氨酸蛋白酶抑制物基因的克隆表达及其活性分析

根据本课题组从克氏原螯虾中新发现的丝氨酸蛋白酶抑制物的基因序列(GenBank登录号CD644775)设计一对引物,应用逆转录-聚合酶链式反应(RT-PCR)技术,从螯虾血淋巴细胞中扩增出丝氨酸蛋白酶抑制物基因PCI188,将其连入原核表达载体pET-32a,转化至大肠杆菌Rosetta株和BL21株中进行蛋白表达,结果该蛋白只在前者表达。表达产物用免疫转印检测,出现50kD的特异性条带,与螯虾PCI188基因编码的蛋白大小相符。将融合蛋白纯化后免疫新西兰兔,用免疫血清与螯虾血淋巴作用后测定酚氧化酶活力,结果显示,酚氧化酶活力有所升高,从而首次证实螯虾PCI188编码的蛋白对丝氨酸蛋白酶有抑制作用。     

SUA41蛋白表达和纯化及其多克隆抗体制备

旨在制备特异性SUA41多克隆抗体,为深入研究其在植物生长发育中的功能提供有力的分子生物学和生物化学的工具。PCR扩增拟南芥SUA41基因中编码280个氨基酸(401-680位氨基酸)的特异片段,经过GATEWAY的DNA重组技术构建了原核表达载体pDEST17-SUA41,用热休克法转化到E.coliBL21(DE3)star感受态细胞,以异丙基β-D-硫代半乳糖苷(IPTG)诱导表达出6×His-SUA41融合蛋白,用8 mol/L尿素缓冲液溶解包涵体并且经过水逐级去除尿素获得提纯的融合蛋白,并利用Western blotting鉴定确认。融合蛋白经Ni金属螯合柱亲和层析得以纯化,用SDS-PAGE进一步纯化。纯化的融合蛋白经过SDS-PAGE后切胶回收,免疫小白兔,制备多抗血清,然后用Western blotting进行检测,鉴定血清特异性和效价。结果显示,融合蛋白6×His-SUA41免疫兔,产生特异性的SUA41兔抗血清,可以检测到细菌和拟南芥组织中SUA41蛋白。用水提纯变性剂尿素溶解的包涵体蛋白具有可行性。制备的特异性SUA41兔抗血清效价高,能够有效地识别大肠杆菌表达的和拟南芥的SUA41蛋白。在有合适的对照情况下,该兔抗血清可以用于分析植物中SUA41蛋白的功能。     

Mx基因稀有密码子和mRNA结构及大肠杆菌表达 优化

通过对稀有密码子和mRNA翻译起始区二级结构的分析, 构建了4种重组表达菌株BL21(DE3)/pET-Mx, Rosseta(DE3)/pET-Mx, BL21(DE3)/pGEX-Mx和Rosseta(DE3)/pGEX-Mx, 在大肠杆菌中进行Mx基因的表达, Rosseta(DE3)/pET-Mx和Rosseta(DE3)/pGEX-Mx重组表达菌中都获得了表达, Western blotting检测到了特异的75 kDa表达产物。实验结果证明稀有密码子和mRNA翻译起始区二级结构对Mx 蛋白表达都有影响, 选择适用于稀有密码子表达的菌株Rosetta(DE3)有利于Mx蛋白的表达, 同时翻译起始区二级结构能值较低的表达载体pGEX-Mx获得的表达量明显增高。实验中首次获得了重组表达鸡全长Mx蛋白的大肠杆菌重组菌。     

Intranasal administration of an Escherichia coli-expressed codon-optimized rotavirus VP6 protein induces protection in mice

We are developing rotavirus vaccines based on the VP6 protein of the human G1P[8] [corrected] [J. Virol. 73 (1999) 7574] CJN strain of rotavirus. One prototype candidate consisting of MBP::VP6::His6, a chimeric protein of maltose-binding protein, VP6 and hexahistidine, was expressed mainly as truncated polypeptides in Escherichia coli BL21(DE3) cells. A possible reason for this extensive truncation is the high frequencies of rare bacterial codons within the rotavirus VP6 gene. Expression of truncated recombinant VP6 was found to be reduced, and expression of complete VP6 protein was simultaneously increased, when the protein was expressed in Rosetta(DE3)pLacI E. coli cells that contain increased amounts of transfer RNAs for a selection of rare codons. The same observation was made when a synthetic codon-optimized CJN-VP6 gene was expressed in E. coli BL21 or Rosetta cells. To increase protein recovery, recombinant E. coli cells were treated with 8M urea. Denatured, full-length MBP::VP6::His6 protein was then purified and used for intranasal vaccination of BALB/c mice (2 doses administered with E. coli heat-labile toxin LT(R192G) as adjuvant). Following oral challenge with the G3P[16] [corrected] [J. Virol. 76 (2002) 560] EDIM strain of murine rotavirus, protection levels against fecal rotavirus shedding were comparable (P>0.05) between groups of mice immunized with denatured codon-optimized or native (not codon-optimized) immunogen with values ranging from 87 to 99%. These protection levels were also comparable to those found after immunization with non-denatured CJN VP6. Thus, expression of complete rotavirus VP6 protein was greatly enhanced by codon optimization, and the protection elicited was not affected by denaturation of recombinant VP6.     

Prokaryotic expression of chicken infectious anemia apoptin protein and characterization of its polyclonal antibodies

In the present study recombinant VP3 (rVP3) was expressed in E. coli BL21 (DE3) (pLysS) and its polyclonal antibodies were characterized. SDS-PAGE analysis revealed that the expression of recombinant protein was maximum when induced with 1.5 mM IPTG for 6 h at 37 degrees C. The 6xHis-tagged fusion protein was purified on Ni-NTA and confirmed by Western blot using CAV specific antiserum. Rabbits were immunized with purified rVP3 to raise anti-VP3 polyclonal antibodies. Polyclonal serum was tested for specificity and used for confirming expression of VP3 in HeLa cells transfected with pcDNA.cav.vp3 by indirect fluorescent antibody test (IFAT), flow cytometry and Western blot. Available purified rVP3 and polyclonal antibodies against VP3 may be useful to understand its functions which may lead to application of VP3 in cancer therapeutics.     

甘蔗花叶病毒CP基因的高效表达和抗血清制备

将甘蔗花叶病毒的CP基因克隆到表达载体pET22b( ),并在大肠杆菌BL21(DE3)中得到高效表达,表达蛋白约占总蛋白的15％。用此蛋白制备了效价高专化性强的抗体。此方法可以解决制备马铃薯Y病毒属病毒的血清时遇到的病毒提纯产量低和寄主蛋白影响等问题。     

青鱼生长激素的重组表达及其多克隆抗体的制备

以含有的青鱼生长激素编码区cDNA的重组质粒pbcGHc为模板,高保真PCR扩增青鱼生长激素（GH）成熟肽cDNA序列,定向插入原核表达载体pET-28a,构建青鱼GH原核表达质粒pET-bcGH。将pET-bcGH转化大肠杆菌BL21(DE3),IPTG诱导青鱼GH基因在大肠杆菌中的融合表达,SDS-PAGE凝胶电泳结果显示一条23 kDa的诱导表达重组青鱼GH带。以草鱼GH多克隆抗体为一抗,Western Blot证明,该重组青鱼GH具有免疫学活性。将经过亲和层析、透析纯化后的重组青鱼GH作为抗原,采用改进的方法对家兔进行皮下免疫注射,获得青鱼GH多克隆抗血清。以该多抗为一抗,Western Blot 可以检测出4 ng的抗原量;并且在青鱼垂体组织抽提液中和血清中检测到一种能与该抗血清作用的大小为21 kDa的蛋白质。这些结果表明本研究得到的青鱼GH多克隆抗血清具有较好的免疫特性。     

小鼠FANCL抗体制备及组织表达谱分析

FANCL是一个范可尼氏贫血新蛋白,它作为泛素E3连接酶催化FANCD2的单一泛素化,在修复DNA损伤、维持染色体稳定的FA途径中起着关键作用。胚胎期FANCL与小鼠原始生殖细胞增殖密切相关,成年睾丸中FANCL与几个生殖细胞特异性蛋白形成一个睾丸特异网络,可能参与影响精子的生成。采用RT-PCR方法从小鼠总RNA中扩增克隆FancL全长cDNA片段,构建表达质粒,在大肠杆菌中表达了6His-FANCL蛋白,用表达蛋白作为抗原免疫新西兰白兔制备了抗FANCL多抗血清。采用镍离子金属螯合柱纯化6His-FANCL蛋白后,通过与活性基团-NHS交联制备了FANCL抗原柱,亲和纯化了FANCL多抗。为了验证抗体活性和特异性,在HEK293T细胞中瞬时表达了HA-FANCL融合蛋白,分别用HA单抗和纯化多抗进行Western印迹分析,结果表明获得了特异性的FANCL抗体。为了观察FANCL在组织中的表达谱,制备了多种小鼠组织匀浆蛋白,使用纯化的FANCL多抗进行Western印迹分析,在脑、心、肺、肝、脾、肾、睾丸、卵巢、子宫和肌肉组织中都检测到FANCL蛋白的表达,说明FANCL在小鼠组织中是广泛表达的,这与其是DNA修复复合物中的重要成员相一致。     

IL-1023-57-PE40分泌表达的初步研究

将IL-1023-57-PE40基因与pelB信号肽融合置于pET-20b构建分泌表达质粒pET-20b-IL-1023-57-PE40,然后将pET-20b-IL-1023-57-PE40分别转化至BL21(DE3),BL21(DE3)pLysS,Rosetta(DE3),E·coliK12TB1,ER2566中。无论是在37℃或是在26℃,亦或在培养基中添加葡萄糖的情况下,IPTG诱导后,IL-1023-57-PE40蛋白只在BL21(DE3)pLysS菌中以可溶分泌形式表达,其中以37℃时培养基中不添加葡萄糖表达量为最高,占菌体蛋白总量的15%,说明蛋白的分泌表达与菌种的选择有关。表达产物经免疫印记检测可被抗PE40的特异抗体识别。通过质粒稳定性实验证明,pET-20b-IL-1023-57-PE40在BL21(DE3)中不稳定,导致蛋白的不表达,在Rosetta(DE3)BL21,E·coliK12TB1,ER2566中稳定但不表达,因此,以Rosetta(DE3)BL21为例,通过SDS-PAGE、DNAStar和ANThewin蛋白分析软件对本室构建的几种PE重组毒素进行比较分析,我们发现:并不是所有PE重组毒素融合信号肽序列后,就能分泌表达,PE重组毒素分泌表达还可能与导向部分的性质有关。     

人SCYL1-BP1重组蛋白的原核表达及分离纯化鉴定

前期研究结果发现,SCYL1-BP1具有细胞周期调控功能,同时具有肿瘤抑制因子的特性。目的:采用基因工程技术,构建SCYL1-BP1的大肠杆菌重组表达菌株,以获得足够量的高纯度目的蛋白,为后面进行一系列药理学检测及新药安全性测试奠定基础。方法:利用从人胎脑cDNA文库中克隆得到SCYL1-BP1基因克隆为模板,经PCR扩增,通过酶切位点克隆到新型原核表达载体pET-28b-SUMO上,转化大肠杆菌表达菌BL21(DE3)。经IPTG诱导表达,摸索优化表达条件,表达产物经Ni柱进行亲和层析纯化,后再进行SDS-PAGE和Western blot等分析鉴定。结果:成功构建了SCYL1-BP1的原核表达工程菌BL21(DE3)/pET-28b-SUMO-SCYL1BP1。SDS-PAGE和Western blot检验结果表明,诱导表达的融合蛋白His6-SUMO-SCYL1BP1的分子量约为65 kDa,主要以可溶的形式存在,且能被His标签抗体和SCYL1-BP1单克隆抗体特异性识别。结论:原核表达并纯化了人SCYL1-BP1融合蛋白,为其后续功能研究及性质实验奠定基础。     

Use of modified BL21(DE3) Escherichia coli cells for high-level expression of recombinant peanut allergens affected by poor codon usage

We previously cloned a panel of peanut allergens by phage display technology. Examination of the codons used in these sequences indicated that most of the cDNAs contain an excess of the least used codons in Escherichia coli, namely AGG/AGA, that correspond to a minor tRNA, the product of the dnaY gene. To achieve high-level expression of the peanut allergens, the cDNAs were subcloned into an expression vector of the pET series (Novagen) in order to produce (His)(10)-tagged fusion proteins in conventional E. coli BL21(DE3) cells. The peanut allergens Ara h 1, Ara h 2, and Ara h 6 with an AGG/AGA codon content of 8-10% were only marginally expressed, whereas the peanut profilin Ara h 5, with an AGG/AGA codon content of only 0.8%, was efficiently expressed in these cells. Hence, by using modified BL21(DE3) E. coli cells, namely BL21-CodonPlus(DE3)-RIL cells (Stratagene) with extra copies of E. coli argU, ileY, and leuW tRNA genes, it was possible to attain high-level expression of the proteins affected by rare codon usage. IPTG-induced expression of several recombinant peanut allergens, such as Ara h 1, Ara h 2, and Ara h 6, was greatly increased in these special cells compared to the expression yield achieved by conventional E. coli hosts. The purification of the soluble and the insoluble fraction of Ara h 2 was performed by metal-affinity chromatography and yielded a total of about 30 mg (His)(10)-tagged recombinant protein per liter of culture of transformed BL21(DE3)CodonPlus-RIL cells. This is over 100 times more than achieved by production of Ara h 2 in conventional BL21(DE3) cells.     

A组人轮状病毒NSP3基因的克隆及其在大肠杆菌中的表达

目的:获得轮状病毒NSP3基因的表达产物及其抗血清。方法:将TB-Chen株轮状病毒NSP3基因插入质粒pETL,构建重组表达质粒pET-NSP3,并转化大肠杆菌BL21(DE3)表达重组蛋白NSP3;用凝胶分离回收的方法纯化该蛋白,免疫豚鼠制备该蛋白的抗血清。结果:构建了重组表达质粒pET-NSP3,并在大肠杆菌中高效表达了重组蛋白NSP3,目的蛋白表达量占菌体总蛋白量的28.6%;有效地纯化了目的蛋白并制备了该蛋白的抗血清,Western印迹表明该抗血清能与重组蛋白NSP3发生特异性免疫反应。结论:通过质粒pETL能高效表达轮状病毒NSP3蛋白,该重组蛋白具有较好的免疫反应性,为进一步研究其结构、功能及免疫学性质奠定了基础。     

转基因香石竹中F3’5’H基因的克隆、表达和免疫学鉴定

在研究转基因香石竹品系月之霓裳（Moonshade）、月之伊人（Moonlite）中外源基因F3’5’H的表达中,本文克隆了F3’5’H全长基因1.5kb,构建获得工程菌株Escherichia coli BL21（DE3）（＋F3＇5＇H）。SDS-PAGE分析的结果显示,该菌株高效表达出F3’5’H重组蛋白,约占菌体总蛋白的30%。用经纯化的F3’5’H重组蛋白作为抗原,制备F3’5’H重组蛋白的抗血清,经ELISA免疫学分析表明,该抗血清的效价为1：25600。Western blot结果表明F3’5’H重组蛋白具有良好的IgG结合活性,且抗血清与转基因香石竹品系月之霓裳和月之伊人中的外源基因F3’5’H所表达的蛋白发生明显的抗原抗体反应。这样,月之霓裳和月之伊人用于评价转基因香石竹品系的环境安全性在我国也得到了验证。