SEB基因定位突变体构建及其重组表达产物生物学活性研究

目的 构建葡萄球菌肠毒素B（SEB）基因及其突变体原核表达系统,了解突变前、后重组表达产物的细胞毒性、促淋巴细胞增殖和抑制肿瘤生长活性的变化.方法 采用突变引物PCR构建SEB基因定位突变体,建立SEB基因及其定位突变体原核表达系统;同时采用Ni-NTA亲和层析法提纯表达的目的 重组蛋白;采用TCID50法测定目的 重组蛋白对Vero细胞的毒性;采用MTT比色法分别检测不同浓度的目的 重组蛋白促使小鼠脾细胞增殖及对抑制KB和HL-60癌细胞株生长的作用.结果 所克隆的SEB基因核苷酸序列与各项研究报道的相似性为100%,3种突变体均在既定位置获得预期的密码子突变.rSEB和各突变体重组蛋白表达量约为细菌总蛋白的40%;rSEB对Vero细胞TCIC50为3.4μg,其突变体重组蛋白分别为3.2～16.8μg;1和5μg/ml的rSEB及突变体重组蛋白rSEB/D9N对小鼠脾细胞均有明显的促增殖作用（P＜0.05）,10和20μg/ml的rSEB及rSEB/D9N促进小鼠脾细胞增殖活性与100μg/ml植物血凝素PHA相似（P＞0.05）.5～20μg/ml的rSEB及rSEB/D9N作用的小鼠脾细胞上清液及其上清液与脾细胞混合物均能有效抑制KB和HL-60细胞生长（P＜0.05）.结论 本研究成功构建了SEB基因突变体及其高效原核表达系统;其中突变体重组蛋白rSEB/D9N细胞毒性较低,促脾细胞增殖和抑制肿瘤细胞生长活性较强,可作为研制升高白细胞、抗肿瘤的SEB相关药物的候选突变体.

乙型脑炎病毒非结构蛋白NS1基因的重组表达及其与黄病毒属病毒抗原抗体反应研究

目的阐明重组表达乙脑病毒非结构蛋白1(Non-structural protein 1,NS1)与包括乙脑病毒在内的多种蚊传黄病毒的抗原抗体反应,以及对乙脑病毒感染患者急性期血清标本的抗原抗体反应。方法本研究使用大肠杆菌原核表达载体(prokaryotic expression vector,pET)系统,重组表达乙脑病毒NS1基因。使用Western Blot实验方法检测重组表达蛋白质与多种,包括乙脑病毒在内的蚊传黄病毒抗体的反应,以及乙脑病毒感染患者急性期血清的抗原抗体反应。结果乙脑病毒(P3株)NS1基因表达产物以包涵体形式存在,经过变性和复性的表达产物在聚丙烯酰胺凝胶电泳(polyacrylamide gel electrophoresis,PAGE,简称变性胶)显示为单一条带,分子量约为45000。进一步的抗原抗体分析结果表明,表达产物与乙脑病毒(蚊虫分离株,脑炎患者分离株)多克隆或者单克隆抗体以及乙脑病毒感染病人急性期血清标本可以获得完全一致的抗原/抗体杂交反应。重组表达产物与蚊传黄病毒,如登革病毒和黄热病毒多克隆抗体之间抗原/抗体杂交反应为阴性,但与西尼罗病毒和墨累谷脑炎病毒多克隆抗体呈现抗原/抗体阳性杂交反应。结论本文成功获得乙脑病毒NS1蛋白的重组表达并分析了重组蛋白对多种蚊传黄病毒及乙脑病毒感染患者标本之间的抗原/抗体反应,研究结果对于阐明乙脑病毒NS1蛋白与蚊传黄病毒之间抗原抗体反应提供了重要的基础数据。本研究所获得重组表达蛋白为进一步研究乙脑病毒NS1蛋白质功能等提供了重要的物质基础。

鼠抗人c-Kit单克隆抗体的制备及其特性鉴定

目的:鼠抗人c-Kit单克隆抗体(mAb)的研制及其生物学特性的鉴定。方法:利用PCR技术获得人c-Kit的胞外免疫球蛋白区编码序列,并将其亚克隆至原核表达载体pQE30,构建出重组表达质粒pQE30-hKitD4-5。测序鉴定正确后转化M15,经IPTG37℃诱导4h后,SDS-PAGE显示融合蛋白(表达产物)以包涵体形式存在。用镍柱对融合蛋白进行纯化,将纯化的蛋白免疫BALB/c小鼠,采用B淋巴细胞杂交瘤技术进行细胞融合,经流式细胞术(FCM)分析和多次克隆化培养,筛选出特异分泌鼠抗人c-Kit分子mAb的杂交瘤细胞株。采用Western blot、Ig亚型快速定性试纸法、FCM等对mAb的生物学特性进行鉴定。结果:成功表达及纯化了人c-Kit重组蛋白,并获得1株持续、稳定分泌鼠抗人c-KitmAb的杂交瘤细胞株,命名为SRJ1。ELISA和Western blot、FCM结果显示了该株mAb能够识别Kasumi白血病细胞株表面表达的天然的c-Kit分子,并与人正常外周血细胞无交叉反应。值得注意的是,Kasumi细胞含有一个不被SRJ1识别的亚群,虽然其表达c-Kit(Ab81mAb的结合正常)。结论:成功构建了原核表达载体pQE30-Kit4-5,并获得高纯度的人pQE30-Kit4-5重组蛋白;成功制备了1株特异性的鼠抗人c-KitmAb杂交瘤。其所分泌的抗体能特异地识别人c-Kit分子,并且可能成为区分细胞表面表达不同c-Kit分子的潜在检测工具。

人心肌营养素在大肠杆菌中的表达纯化和活性鉴定

目的 利用大肠杆菌高效表达可溶性具有生物学活性的重组huCT 1蛋白。方法 采用PCR及T A克隆将huCT 1开放阅读框基因克隆到pMD 18T载体上 ,再构建原核表达载体pGEX2T huCT1。在不同温度不同时间 ,通过IPTG诱导pGEX2T huCT1在DH5a大肠杆菌中表达 ,SDS PAGE分析表达量和可溶性蛋白比例。GST亲和柱纯化huCT 1融合蛋白 ,凝血酶酶切融合蛋白并纯化。坐骨神经切断模型观察重组huCT 1对脊髓前角神经元的存活作用。结果 构建了huCT 1的融合表达载体pGEX2T huCT1。通过IPTG诱导 ,发现 2 9℃诱导 4h ,目的蛋白表达量占全菌的 1 5 ,可溶性蛋白与包涵体比为 2 5。对其进行亲和柱纯化 ,GST huCT 1融合蛋白纯度达到 85 %以上。融合蛋白酶切后 ,重组huCT 1蛋白纯度达到80 %以上。发现原核表达重组huCT 1蛋白能挽救 5 5 %成年大鼠脊髓运动神经元的存活。结论 成功地获取了具有生物活性的huCT

Construction of prokaryotic expression system of TGF-β1 epitope gene and identification of recombinant fusion protein immunity

AIM： To insert the constructed TGF-β1 epitope gene into the el loop of C-terminus of truncated hepatitis B core antigen to increase TGF-β1 antigenicity in its prokaryotic expression system and to identify immunity of the expressed recombinant protein in order to exploit the possibility for obtaining anti- TGF-β1 vaccine. METHODS： The TGF-β1 encoding epitope gene （the mature TGF-β1 from 78-109 amino acid residues, TGF-β1^32） was amplified by polymerase chain reaction from the recombinant pGEM-7z/ TGF-β1 ^32 vector. The HBcAg gene fragments （encoding HBcAg from 1-71 and 89-144 amino acid residues） were amplified from PYTAI- HBcAg vector. The recombinant vector pGEMEX-1 was used to insert HBcAg1-71, TGF-β1^32 and HBcAg89-144 into restrictive endonuclease enzyme and ligated with T4 Ugase. The fusion gene fragments HBc.Ag1-71-TGF-β1^32 HBcAg89-144 were recloned to pET28a（＋） and the DNA sequence was confirmed by the dideoxy chain termination method. The recombinant vector pET28a （＋）/ CTC was transformed and expressed in E. coli BL21 （DE3） under induction of IPTG. After purification with Ni^＋2 NTA agarose resins, the antigenicity of purified protein was detected by ELISA and Western blot and visualized under electron microscope. RESULTS： Enzyme digestion analysis and sequencing showed that TGF-β1 epitope gene was inserted into the el loop of C-terminus of truncated hepatitis B core antigen. SDS-PAGE analysis showed that relative molecular mass （Mr） of the expressed product by pET28a （＋）/CTC was Mr 24 600.The output of the target recombinant protein was approximately 34.8% of the total bacterial protein,mainly presented in the form of inclusion body. Western blotting and ELISA demonstrated that the fusion protein could combine with anti-TGF-β1 polyclonal IgG but not with anti-HBcAg. The purity of protein was about 90 % and the protein was in the form of self-assembling particles visualized under electron microscope. This fusion protein had good anti-TGF-β1 antigenicity and could be used as anti-TGF-β1 vaccine. CONCLUSION： A recombinant prokaryotic expression system with high expression efficiency of the target TGF-β1 epitope gene was successfully established. The fusion protein is in the form of self-assembling particles and HBcAg can increase the antigenicity of TGF-β1. The expressed TGF-β1 epitope gene shows good immunogenicity and antigenicity.

Gene cloning and prokaryotic expression of recombinant flagellin A from Vibrio parahaemolyticus

The Gram-negative Vibrio parahaemolyticus is a common pathogen in humans and marine animals. Bacteria flagellins play an important role during infection and induction of the host immune response. Thus, flagellin proteins are an ideal target for vaccines. We amplified the complete flagellin subunit gene （tTaA） from V. parahaemolyticus ATCC 17802. We then cloned and expressed the gene into Escherichia coli BL21 （DE3） cells. The gene coded for a protein that was 62.78 kDa. We purified and characterized the protein using Ni-NTA affinity chromatography and Anti-His antibody Western blotting, respectively. Our results provide a basis for further studies into the utility of the FlaA protein as a vaccine candidate against infection by Vibrio parahaemolyticus. In addition, the purified FlaA protein can he used for further functional and structural studies.

Prokaryotic expression of recombinant human p75NTR-Fc fusion protein and its effect on the neurite outgrowth of dorsal root ganglia neuron

Objective： To clone, express, and identify the extracellular domain gene of human p75 neurotrophin receptor with IgG-Fe （hp75NTR-Fc） in prokaryotic expression system, and investigate the effect of the recombinant protein on dorsal root ganglia （DRG） neuron neurites. Methods： The hp75NTR-Fc coding sequence was amplified from pcDNA-hp75NTR-Fc by polymerase chain reaction （PCR） and subcloned into vector pET30a （＋）, in which hp75NTR-Fc expression was controlled under the T7 promoter. The recombinant vectors were amplified in E. coli DH5α and identified by PCR, enzyme digestion and sequencing, and then transformed into E. coli BL21 （DE3）. The expression product was analyzed with SDS-PAGE and Western blot. Then after the recombinant protein purified with Protein A affinity chromatograph, and renaturated with dialysis, respectively, the effect of the recombinant protein on DRG neuron neuritis was further investigated. Results： The results of PCR, enzyme digestion, and sequencing demonstrated the success of inserting the hp75NTR-Fc fragment into vector pET30a （＋）. SDS-PAGE and Western blot showed a positive protein band with molecular weight about 50 kD in the expression product, which is accordant with the interest protein, and this band could be specifically recognized by rabbit anti-NGFRp75 antibody. The purified infusion protein following dialysis could promote neurite outgrowth of DRG neurons cultured with myelin-associated glycoprotein （MAG）. Conclusion： The hp75NTR-Fc coding sequence was subcloned into the expression vector pET30a （＋） correctly and expressed successfully in the prokaryotie expression system. The infusion protein could promote neurite outgrowth of DRG neurons cultured with MAG.

三七几丁质酶基因PnCHI1的功能分析

几丁质酶（chitinase）是一种能够将几丁质水解成N-乙酰葡糖胺的糖苷酶,广泛存在于植物细胞中,是抗真菌防卫反应体系的重要组成部分。该文深入分析了1种三七几丁质酶基因PnCHI1的功能。构建PnCHI1的亚细胞定位载体,转入洋葱表皮细胞中瞬时表达,在激光扫描共聚焦显微镜下发现PnCHI1定位于细胞壁中。构建PnCHI1的原核表达载体,诱导并纯化获得重组蛋白,体外平板抑菌实验结果显示PnCHI1原核重组蛋白对尖孢镰刀菌、茄腐镰刀菌、轮枝镰刀菌3种三七根腐病菌的菌丝生长具有很强的抑制活性。采用反向遗传学技术验证PnCHI1的功能,通过根癌农杆菌介导将PnCHI1转入烟草中过量表达。qRT-PCR分析结果表明PnCHI1在T2代转基因烟草中大量表达,同时叶片接种实验显示PnCHI1转基因烟草对茄腐镰刀菌的抗性增强明显。结论：PnCHI1是定位于细胞壁的几丁质酶,体外能抑制几种三七根腐病真菌,在烟草过表达大大提高了烟草对茄腐镰刀菌的抗性,推测PnCHI1是三七中参与根腐病防卫反应的重要抗病基因。