HIV-1 gp41的酵母表面展示及表达优化

以His标签检测蛋白的表达, 利用酿酒酵母表面展示系统, 成功地将HIV-1 gp41片段锚定在酵母表面, 并检测到gp41的活性。以pMD18T-gp41为模板, 通过PCR技术克隆了gp41基因, 将gp41基因通过双酶切连接到载体pICAS-His上,构建了gp41酵母表面展示载体, 并将其转化至酿酒酵母(Saccharomyces cerevisiae)MT8-1中。重组菌经培养, 利用免疫荧光染色方法进行染色, 显微镜观察发现重组酵母细胞表面有绿色荧光, 流式细胞仪结果进一步证实gp41正确折叠展示于酵母细胞表面。采用不同浓度的葡萄糖培养基进行表达优化。当葡萄糖浓度为1%时, 82.46%的酵母细胞表达了gp41抗原; 随着葡萄糖浓度升高, 蛋白表达受到抑制。     

利用荧光蛋白研究产甘油假丝酵母胞浆3-磷酸甘油脱氢酶基因CgGPD启动子

[目的]克隆产甘油假丝酵母(Candida glycerinogenes)胞浆3-磷酸甘油脱氢酶基因CgGPD的启动子(PCggpd),并通过报告基因gfp的差异表达来研究葡萄糖浓度对PCggpd在酿酒酵母(Saccharomyces cerevisiae)中的诱导特性.[方法]采用PCR扩增的方法分别从产甘油假丝酵母基因组和pCAMBIA1302载体中克隆出CgGPD的启动序列PCggpd和绿色荧光蛋白基因gfp.将两个基因同时构建到酿酒酵母表达载体pYX212-zeocin中,构建时将绿色荧光蛋白基因gfp置于CgGPD的启动序列下游,获得重组质粒pYX212-zeocin-PCggpd-gfp.通过电击转化酿酒酵母W303-lA.将重组酿酒酵母S.cerevisiae W303-1A-GFP置于不同葡萄糖浓度培养基中进行培养,利用荧光显微技术对其进行荧光检测.[结果]重组酿酒酵母能产生稳定的荧光,当葡萄糖浓度为2%时,重组酿酒酵母在YEPD培养基中产生较弱的荧光,随着葡萄糖浓度的升高,荧光强度有明显的增强.[结论]PCggpd属于环境胁迫诱导型启动子,高浓度的葡萄糖能诱导PCggpd启动绿色荧光蛋白的高水平表达,这对完善产甘油假丝酵母的遗传背景研究,阐明其高产甘油的机理具有重要意义.     

南极假丝酵母脂肪酶B的酿酒酵母表面展示及其催化己酸乙酯的合成

从南极假丝酵母(Candida antarctica)基因组克隆得到南极假丝酵母脂肪酶B(Candida antarctica Lipase B, CALB)全基因片段, 利用连接肽celA Linker将CALB与酿酒酵母细胞表面展示蛋白a-凝集素的C端连接融合, 构建表面展示载体pICAS-celAL-CALB, 转化酵母后获得重组酵母菌Saccharomyces cerevisiae pICAS-celAL-CALB。该重组酵母菌经葡萄糖诱导表达及分析, 表明CALB已在酿酒酵母细胞表面成功展示, 水解活力达26.26 u/(g·dry cell)。重组酵母菌经冻干能有效地实现在非水相中全细胞催化己酸和乙醇酯化合成己酸乙酯。反应物己酸与乙醇的摩尔比为1:1.25, 己酸乙酯的产率为98.0%, 具有较好的操作稳定性。     

南极假丝酵母脂肪酶B的酿酒酵母表面展示及其催化己酸乙酯的合成

从南极假丝酵母(Candida antarctica)基因组克隆得到南极假丝酵母脂肪酶B(Candida antarctica Lipase B, CALB)全基因片段, 利用连接肽celA Linker将CALB与酿酒酵母细胞表面展示蛋白a-凝集素的C端连接融合, 构建表面展示载体pICAS-celAL-CALB, 转化酵母后获得重组酵母菌Saccharomyces cerevisiae pICAS-celAL-CALB。该重组酵母菌经葡萄糖诱导表达及分析, 表明CALB已在酿酒酵母细胞表面成功展示, 水解活力达26.26 u/(g·dry cell)。重组酵母菌经冻干能有效地实现在非水相中全细胞催化己酸和乙醇酯化合成己酸乙酯。反应物己酸与乙醇的摩尔比为1:1.25, 己酸乙酯的产率为98.0%, 具有较好的操作稳定性。     

酵母表面展示T载体构建及目的蛋白的表面展示

构建一种能对PCR产物进行直接克隆并展示于酵母表面的新型T载体。根据酵母表面展示载体p YD1多克隆位点序列设计出利用两端带有XcmⅠ内切酶酶切位点的含有黄色荧光蛋白基因的XcmⅠ酶切盒,通过NheⅠ和XhoⅠ酶切位点插入到p YD1载体上形成质粒p YD-YFP,并对其进行酶切鉴定和DNA测序分析,再经XcmⅠ酶切后形成两端带有d T的表面展示T载体。利用PCR扩增两个含有荧光蛋白的融合蛋白PCAD-CFP和PSR-Ds Red的基因并直接克隆到所构建的T载体中,检测其表达功能。酶切鉴定和DNA测序结果显示PCAD-CFP和PSR-Ds Red正确插入载体上,分别转化至酿酒酵母EBY100中,激光共聚焦显微镜下观察到相应的荧光的酵母,表明克隆有融合蛋白基因片段的载体成功在酵母细胞中进行表面展示,证明了所构建的酵母表面展示T载体具有直接克隆和表面展示目的蛋白的功能。     

酿酒酵母表面展示鲑鱼降钙素多肽的研究

目的:实现酿酒酵母表面展示鲑鱼降钙素.方法:人工合成鲑鱼降钙素(Salmon cacitonin,sCT)编码基因,克隆到表面展示载体M-pYD1上.用NocⅠ酶切重组质粒M-pYD1-sCT和空白质粒M-pYD1,回收sCT和V5表达框片段后分别以LiAC法转化酿酒酵母EBY100菌株,分别得到重组酵母yAGA2-sCT和yAGA2-V5.两种重组酵母分别经半乳糖诱导表达后,采用FITC荧光标记酵母表面展示的sCT和V5多肽,分别用荧光显微镜和流式细胞仪进行定性和定量分析.结果:诱导12h后,荧光显微镜下清晰观测到了工程菌表面有重组sCT,流式细胞分析结果表明10000个细胞中65.2%的yAGA2-sCT菌株表达了外源sCT,52.4%的yAGA2-V5菌株表达V5.结论:利用酿酒酵母表面展示鲑鱼降钙素多肽获得了成功,为口服型鲑鱼降钙素的研发奠定了基础.     

鲤春病毒血症病毒糖蛋白酵母表面展示系统的建立

糖蛋白(Glycoprotein, G)作为鲤春病毒血症病毒(Spring Virernia of Carp Virus, SVCV)主要的抗原蛋白, 已成为现阶段SVCV病毒检测、抗体制备以及疫苗研制的热点。为了对其进行酵母表面展示, 研究以SVCV-shlj1分离株基因组为模板, 通过RT-PCR技术, 体外扩增获得SVCV表面糖蛋白的基因开放阅读框(1530 bp)片段, 将其克隆至酵母表面展示载体pYD1, 构建重组质粒pYD1-G。利用电转化方法将重组质粒pYD1-G导入酿酒酵母EBY100感受态细胞, 经YNB选择培养基筛选和菌液PCR的鉴定, 挑选出阳性转化子(命名为EBY100-pYD1-G), 对其进行2%半乳糖诱导。利用细胞免疫荧光和流式细胞仪检测G蛋白的酵母表面展示情况。细胞免疫荧光结果显示, 诱导后的酵母细胞EBY100-pYD1-G能产生特异性红色荧光, 且随着诱导时间的增加, 红色荧光的酵母细胞所占比例不断增加, 各组之间差异显著(P< 0.05)。流式细胞仪检测结果显示, 酵母细胞的荧光强度与诱导时间呈正比, 其中诱导48h与72h的酵母细胞荧光强度不存在显著差异, 基本趋于稳定不变的状态。因此, 选取诱导48h为酵母表面展示的最佳诱导时间。上述研究结果表明SVCV的G蛋白已经成功展示于酿酒酵母细胞表面, 研究为鲤春病毒血症酵母口服疫苗的研发奠定了前期基础。     

酵母表面展示分选酶底物用于分选酶活性检测

摘要：【目的】以EGFP标签检测分选酶底物QALPETGEE在毕赤酵母表面的表达,然后将酵母表面展示的底物与分选酶相互作用以检测分选酶活性。【方法】以pcDNA-myc-his-EGFP为模板,通过PCR技术将QALPETGEE-linker-EGFP基因连接到穿梭载体pKFS上,构建QALPETGEE-linker-EGFP酵母表面展示载体后转化至毕赤酵母（Pichia pastoris）GS115中。重组菌经培养,利用荧光显微镜检测重组酵母的荧光强度,然后通过荧光分光光度计检测分选酶与底物相互作用后产     

海藻糖合酶在毕赤酵母表面的展示

海藻糖合酶能够利用麦芽糖一步法转化生产海藻糖,其底物专一性较高,该酶体系生产工艺简单,不受底物麦芽糖浓度的影响,是工业生产海藻糖的首选。为获得具有生产海藻糖合酶能力的毕赤酵母表面展示载体,实验以筛选的Pseudomonas putide P06海藻糖合酶基因为模板,PCR扩增得到海藻糖合酶基因(tres,2064 bp),连接至pPICZαA质粒中,获得重组质粒pPICZαA-tres。以来自酿酒酵母的共价连接细胞壁的Pir系列蛋白的Pir1p成熟肽蛋白作为毕赤酵母表面展示的锚定蛋白,利用PCR技术扩增得到pir1p(847 bp),连接至重组质粒pPICZαA-tres中,获得重组质粒pPICZαA-tres-pir1p。将重组质粒电击转入毕赤酵母GS115中,利用α-factor信号肽将蛋白引导分泌至细胞壁展示于毕赤酵母表面。通过Zeocin抗性筛选,挑选出阳性克隆子并摇瓶发酵。发酵产物经离心、破碎并使用昆布多糖酶水解,洗脱,结果显示,SDS-聚丙烯酰胺凝胶电泳分析可见明显融合蛋白条带,表明海藻糖合酶已成功地锚定在毕赤酵母。将重组毕赤酵母使用pH 7.5的缓冲液清洗并重悬,与底物浓度为30%的麦芽糖在30℃~60℃水浴条件下作用2 h,反应产物利用HPLC检测,能够检测到酶学活性。在优化后的条件pH 7.5,50℃,表面展示海藻糖合酶酶活达到300.65 U/g。40℃~50℃酶活较稳定,保温60 min,残留酶活相对活力达75%以上;最适反应pH值为7.5,并在碱性环境下稳定。     

酵母细胞表面展示载体的构建及功能验证

目的:构建酵母细胞表面展示载体。方法:通过酶切连接方法在pADH1载体中插入信号肽、α-凝集素(含连接子)编码序列构建表面展示载体,并用EGFP来验证该载体的功能。结果:得到了267 bp的信号肽序列、1 623 bp的凝集素编码序列和717 bp的绿色荧光蛋白编码序列,酵母细胞表面展示载体被成功构建,且绿色荧光蛋白被插入到pADH1-agg中后,阳性转化子能在荧光显微镜下呈现绿色荧光。结论:这说明酵母细胞表面展示载体已经构建成功,并能成功表达和展示蛋白在酵母细胞表面。该载体的构建成功将为利用酵母表面展示系统表达和展示相关蛋白提供了平台。     

HIV-1 and its transmembrane protein gp41 bind to different Candida species modulating adhesion

Oral candidiasis in HIV-1-infected individuals is widely believed to be triggered by the acquired T-lymphocyte immunodeficiency. Recently, binding of the HIV-1 envelope protein gp160 and its subunit gp41, and also of the whole virus itself, to Candida albicans has been shown. The present study shows that, in addition to C. albicans, HIV-1 gp41 also binds to yeast and hyphal forms of Candida dubliniensis, a species which is closely related to C. albicans, and to Candida tropicalis but not to Candida krusei, Candida glabrata or Saccharomyces cerevisiae. The previous finding that gp41 binding to C. albicans augments fungal virulence in vitro is supported by the observation that the yeast showed an enhanced adhesion to HIV-infected H9 cells in comparison to uninfected cells. In line with these results soluble gp41 itself reduced binding of C. albicans to both endothelial and epithelial cell lines, confirming a dominant role of the gp41 binding moiety on the surface of Candida for adhesion. Surface-associated secreted aspartic proteinases (Saps) play an important role in candidial adhesion, but are not likely to be involved in the interaction as gp41 binding to the C. albicans parental wild-type strain was comparable to that of three different isogenic Sap deletion mutants. Furthermore, gp41 binding to the yeast killer toxin-susceptible C. albicans strain 10S was not inhibitable by an anti-YKT receptor antibody. In conclusion, HIV-1 interacts with different clinically important Candida spp., and may thereby affect the outcome of the respective fungal infection.     

扣囊复膜孢酵母b-葡萄糖苷酶基因在工业酿酒酵母中的表达

本文以工业酿酒酵母菌株( Saccharomyces cerevisiae Y )为研究对象,针对其复杂的生理生化遗传特性,建立了相对应的转化体系。以pRS41H质粒为基础载体,构建了含有工业酿酒酵母自身的gpd2启动子、终止子和扣囊复膜孢酵母的b-葡萄糖苷酶基因bgl的重组质粒pRS-gb。电击转化进入工业酿酒酵母细胞,潮霉素抗性筛选,获得重组菌。该重组菌可以在以纤维二糖为唯一碳源的培养基中生长,培养36 h,b-葡萄糖苷酶酶活达到0.967 u/ml。以纤维二糖为唯一碳源的酒精发酵中,酒精度可以达到0.92 g/l。这对工业生产中利用纤维素为原料发酵生产酒精具有重要意义。     

Construction of a novel system for cell surface display of heterologous proteins on <Emphasis Type="Italic">Pichia pastoris</Emphasis>

A versatile vector was developed for heterologous proteins display on the cell surface of Pichia pastoris using the C-terminal half of alpha-agglutinin from Saccharomyces cerevisiae as a membrane anchor under the control of the alcohol oxidase 1 promoter (pAOX1). Multiple cloning sites and the sequence encoding the Xpress epitope (-Asp-Leu-Tyr-Asp-Asp-Asp-Asp-Lys-) were introduced into the vector for insertion of heterologous genes and selective cleavage of target proteins. Enhanced green fluorescence protein (EGFP) was used as a model protein to check the function of this vector. The expression of EGFP on the P. pastoris surface was confirmed by confocal laser scanning microscopy. Fluorescence microscopy and western blot analysis confirmed that EGFP can be successfully cleaved from the cell surface by treating with enterokinase.     

Immobilization of Saccharomyces cerevisiae cells to protein G-Sepharose by cell wall engineering

In this work, we explored the possibility of using the targeting of a heterologous protein to the cell wall of Saccharomyces cerevisiae, by fusing it to a cell wall protein, to construct yeast strains whose cells display on their surface proteins that bind to a matrix, so as to achieve the immobilization of the whole cells. With this aim, we created a gene fusion that comprises the region responsible for attachment of a cell wall protein to the cell wall, and the IgG binding region of staphylococcal protein A, and expressed it in the mnn1mnn9 strain of S. cerevisiae. The surface display of the protein A-Icwp fusion protein was positively monitored; however, direct immobilization of the cells on an IgG-Sepharose matrix did not produce the expected results, probably due to the fusion protein not being completely exposed on the surface of the cells. To solve this problem we incubated the cells first with rabbit preimmune serum and then with goat anti-rabbit IgGs, so as to create a complex (yeast cell-protein A-rabbit IgG-goat IgG). Cells treated in this way were successfully immobilized on a protein G-Sepharose matrix, due to the binding properties of goat IgGs to streptococcal protein G.     

Isolation and deduced amino acid sequence of the gene encoding gp115, a yeast glycophospholipid-anchored protein containing a serine-rich region

gp115 is a N- and O-glycosylated protein of Saccharomyces cerevisiae. It is also modified by addition of glycosylphosphatidylinositol, which anchors the protein to the plasma membrane. The gene encoding gp115 (GGP1) has been cloned by a two-step procedure. By an immunoscreening of a yeast genomic DNA library in the expression vector lambda gt11, a 3'-terminal 0.9-kilobase portion of the gene has been isolated and then used as a molecular probe to screen a yeast genomic DNA library in YEp24. In this way, the whole GGP1 gene has been cloned. Its identity with the gp115 gene has been confirmed by gene disruption, which has also indicated that the function of gp115 is not essential for cell viability. The features of the sequence are also entirely consistent with it corresponding to the gp115 gene. The nucleotide sequence of GGP1 predicts a 60-kDa polypeptide, in agreement with the molecular mass of the gp115 precursor detected in sec53 mutant cells at restrictive temperature. Two hydrophobic sequences, one NH2- and the other COOH-terminal were found. The former has the features of the cleavable signal sequence, which allows the entry of proteins in the secretory pathway. The latter could be the signal sequence that has to be removed during the addition of glycosylphosphatidylinositol. The predicted amino acid sequence of gp115 shows 10 sequons for N-glycosylation and a high proportion of serine-threonine residues (22%) that could provide several sites for O-glycosylation. The unusual concentration of 27 serines in the COOH-terminal portion of the protein shares homology with a similar polyserine repeat of the serine repeat antigen (SERA protein) of Plasmodium falciparum. A two-dimensional analysis of the "in vitro" translational product of the GGP1 mRNA has been carried out, allowing the identification of the "in vivo" gp115 precursor in a two-dimensional gel.     

Screening of a molecule endowing Saccharomyces cerevisiae with n-nonane-tolerance from a combinatorial random protein library

A combinatorial random protein library was constructed from random DNA fragments generated by "DNA random priming", an improved method of "random-priming recombination" using random-sequence primers and template cDNA from the yeast Saccharomyces cerevisiae. In order to express this library on the yeast cell surface, a yeast multicopy cassette vector was constructed, in which the random-protein-encoding DNA fragments were fused to a gene encoding the C-terminal 320 amino acids of alpha-agglutinin. Fluorescent labeling of the immuno-reaction of RGS(His)(6) epitope confirmed the surface display of random proteins. The surface display of heterologous random proteins on yeast cells will have a wide application. As an example, an n-nonane-tolerant yeast strain that could grow very well in nonane-overlaid culture medium was screened out from transformants displaying this combinatorial library. n-Nonane tolerance was dependent on the transformed plasmid, and the related protein was confirmed to localize on the cell surface by papain treatment and immunofluorescent labeling. Analysis of this displayed protein was also carried out. This strain is the first one to have been endowed artificially with organic solvent tolerance. This is a good example of creating cells exhibiting new phenotypes using a combinatorial protein library.     

Cell surface expression of bacterial esterase A by Saccharomyces cerevisiae and its enhancement by constitutive activation of the cellular unfolded protein response

Yeast cell surface display is a powerful tool for expression and immobilization of biocatalytically active proteins on a unicellular eukaryote. Here bacterial carboxylesterase EstA from Burkholderia gladioli was covalently anchored into the cell wall of Saccharomyces cerevisiae by in-frame fusion to the endogenous yeast proteins Kre1p, Cwp2p, and Flo1p. When p-nitrophenyl acetate was used as a substrate, the esterase specific activities of yeast expressing the protein fusions were 103 mU mg(-1) protein for Kre1/EstA/Cwp2p and 72 mU mg(-1) protein for Kre1/EstA/Flo1p. In vivo cell wall targeting was confirmed by esterase solubilization after laminarinase treatment and immunofluorescence microscopy. EstA expression resulted in cell wall-associated esterase activities of 2.72 U mg(-1) protein for Kre1/EstA/Cwp2p and 1.27 U mg(-1) protein for Kre1/EstA/Flo1p. Furthermore, esterase display on the yeast cell surface enabled the cells to effectively grow on the esterase-dependent carbon source glycerol triacetate (Triacetin). In the case of Kre1/EstA/Flo1p, in vivo maturation within the yeast secretory pathway and final incorporation into the wall were further enhanced when there was constitutive activation of the unfolded protein response pathway. Our results demonstrate that esterase cell surface display in yeast, which, as shown here, is remarkably more effective than EstA surface display in Escherichia coli, can be further optimized by activating the protein folding machinery in the eukaryotic secretion pathway.     

絮凝选择载体的构建及β葡萄糖苷酶基因在酿酒酵母中的表达

从强絮凝酿酒酵母(Saccharomyces cerevisiae)ABXL-1D菌株中用PCRA-法扩增到絮凝基因(Flocculation gene,FLO1),构建以絮凝基因作选择标记的酿酒酵母表达栽体：用该栽体表达Bacillus polymyxa的β-葡萄糖苷酶基因,转化子可直接从沉淀中筛选。摇瓶培养细胞得到的β-葡萄糖苷酶比活力为3．91u／mg蛋白。在发酵葡萄糖和纤维二糖混合底物时,转化子的葡萄糖残存量明显低于受体菌。这将有利于利用纤维素发酵生产酒精。     

Development of combinatorial bioengineering using yeast cell surface display--order-made design of cell and protein for bio-monitoring

A genetic system to display proteins as their active and functional forms on the cell surface of yeast, Saccharomyces cerevisiae, has been exploited. Surface-engineered (arming) cells displaying amylase or cellulase could assimilate starch or cellulose as the sole carbon source, although S. cerevisiae can not intrinsically assimilate them. Arming cells with a green fluorescent protein (GFP) from Aequorea victoria can emit green fluorescence from the cell surface in response to the environmental conditions. From these results, we attempted to construct a system to monitor the foreign protein production in yeast by simultaneous displaying the enhanced GFP (EGFP). The expression in yeast of the Escherichia coli beta-galactosidase-encoding gene was examined as an example of intracellular production and that of the human interferon-alpha (omega, IFN-omega)-encoding gene as an example of extracellular production. Their productions and the simultaneous surface-display of EGFP as a reporter were controlled by the same promoter, GAL1. The relationship among fluorescence signals and their productions was evaluated. The surface-display system, unlike one using tag-proteins, would be able to facilitate the monitoring of native protein productions in bioprocesses using living cells in real time by the combination of promoters and GFP variants.