Detection of a species-specific antigen of Gardnerella vaginalis by Western blot analysis

Western blot analysis was used to identify antigenic components of Gardnerella vaginalis. Polypeptides bound to nitrocellulose membranes were probed with murine antisera raised to two strains of G. vaginalis, and antibody-antigen complexes were detected with 125I-labelled antimouse immunoglobulin followed by autoradiography. Although there was inter-strain variation in immunogenic polypeptide profiles, all 23 strains of G. vaginalis examined contained a common antigen of molecular mass 41 kDa. This antigen was not found in any of six other bacterial genera.     

Identification of a Gardnerella vaginalis Hemoglobin-Binding Protein

Previous studies have shown that Gardnerella vaginalis can utilize human hemoglobin as a sole source of iron. In this study, the interaction between human hemoglobin and G. vaginalis cells was investigated. With a solid phase dot blot assay, G. vaginalis cells were shown to bind digoxigenin (DIG)-labeled human hemoglobin. A human hemoglobin-binding protein with an estimated molecular weight of 124 kilodaltons (kDa) was detected by Western blot analysis of G. vaginalis proteins. The hemoglobin-binding activity of this protein was found to be heat stable and was observed in G. vaginalis cells grown under iron-restrictive and iron-replete conditions. The 124-kDa hemoglobin-binding protein was not detected from intact G. vaginalis cells treated with trypsin prior to Western blot analysis, suggesting that this protein was surface exposed. Received: 26 June 2000 / Accepted: 21 July 2000     

Differential expression of protein phosphatase type 1 isotypes and nucleolin during cell cycle arrest

In the present study, we examined the expression and cytolocalization of protein phosphatase type 1 (PP1) isoforms and nucleolin in human osteoblastic cell line MG63 cells at two boundaries in the cell cycle. We treated MG63 cells with hydroxyurea and nocodazole to arrest the cells at the G(1)/S and G(2)/M boundaries, respectively. As judged from the results of Western blot analysis, PP1 isoforms were expressed differently at each boundary of the cell cycle. Nucleolin was also shown to have a different expression pattern at each boundary. In the hydroxyurea-treated cells, nucleolus-like bodies were bigger in size and decreased in number compared with those in asynchronized cells. However, the subcellular localization of PP1s and nucleolin was not changed. Anti-nucleolin antibody interacted with 110-kDa and 95-kDa proteins present in asynchronized cells and in the cells treated with hydroxyurea. Treatment of the cells with nocodazole decreased the level of the 95-kDa form of nucleolin. In the nocodazole-treated cells, it was impossible to distinguish the distribution of each protein. The phosphorylation status of nucleolin in the cell cycle arrested samples was examined by 2D-IEF-PAGE followed by Western blot analysis. In the case of asynchronized cells or hydroxyurea-treated ones, nucleolin was located at a basic isoelectric point (dephosphorylated status); whereas in the G(2)/M arrest cells, the isoelectric point of nucleolin shifted to an acidic status, indicating that nucleolin was phosphorylated. The present results indicate that PP1 and nucleolin were differently expressed at G(1)/S and G(2)/M boundaries of the cell cycle and acted in a different fashion during cell-cycle progression.     

Kozak序列+4G提高绿色荧光蛋白在HEK293细胞中的表达

构建含不同Kozak序列的绿色荧光蛋白(GFP)基因真核表达载体, 并检测它们在HEK293细胞中的表达差异。 通过设计突变的PCR引物改变目的基因GFP的Kozak序列, +4 位碱基分别为A和G, 且不改变氨基酸编码, 将PCR扩增的GFP片段与载体pcDNA3.1进行酶切、连接、转化、鉴定。成功构建的pHGFP-A, pHGFP-G质粒采用脂质体法转染HEK293细胞, 荧光显微镜下观察绿色荧光表达, 流式细胞术检测目的蛋白GFP的荧光表达阳性率, Western blot检测目的蛋白GFP的表达。构建的两质粒均能有效转染 HEK293细胞, 其中流式细胞术分析显示: pHGFP-A组GFP阳性率约为15%, pHGFP-G组GFP阳性率约为45%; Western blot 显示pHGFP-G的GFP表达量约为pHGFP-A的GFP表达量3.87倍。结果表明, Kozak序列+4G(?3位为嘌呤碱基时)在蛋白表达中发挥重要作用, 可以使绿色荧光蛋白GFP在HEK293细胞中的表达量提高约4倍。     

Kozak序列+4G提高绿色荧光蛋白在HEK293细胞中的表达

构建含不同Kozak序列的绿色荧光蛋白(GFP)基因真核表达载体, 并检测它们在HEK293细胞中的表达差异。 通过设计突变的PCR引物改变目的基因GFP的Kozak序列, +4 位碱基分别为A和G, 且不改变氨基酸编码, 将PCR扩增的GFP片段与载体pcDNA3.1进行酶切、连接、转化、鉴定。成功构建的pHGFP-A, pHGFP-G质粒采用脂质体法转染HEK293细胞, 荧光显微镜下观察绿色荧光表达, 流式细胞术检测目的蛋白GFP的荧光表达阳性率, Western blot检测目的蛋白GFP的表达。构建的两质粒均能有效转染 HEK293细胞, 其中流式细胞术分析显示: pHGFP-A组GFP阳性率约为15%, pHGFP-G组GFP阳性率约为45%; Western blot 显示pHGFP-G的GFP表达量约为pHGFP-A的GFP表达量3.87倍。结果表明, Kozak序列+4G(?3位为嘌呤碱基时)在蛋白表达中发挥重要作用, 可以使绿色荧光蛋白GFP在HEK293细胞中的表达量提高约4倍。     

Evidence for Gardnerella vaginalis uptake and internalization by squamous vaginal epithelial cells: implications for the pathogenesis of bacterial vaginosis

Bacterial vaginosis (BV), a common condition seen in premenopausal women, is associated with preterm labor, pelvic inflammatory disease, and delivery of low birth weight infants. Gardnerella vaginalis is the predominant bacterial species associated with BV, although its exact role in the pathology of BV is unknown. Using immunofluorescence, confocal and transmission electron microscopy, we found that VK2 vaginal epithelial cells take up G. vaginalis after exposure to the bacteria. Confocal microscopy also indicated the presence of internalized G. vaginalis within vaginal epithelial cells obtained from a subject with BV. Using VK2 cells and (35)S labeled bacteria in an invasion assay, we found that a 1 h uptake of G. vaginalis was 21.8-fold higher than heat-killed G. vaginalis, 84-fold compared to Lactobacillus acidophilus and 6.6-fold compared to Lactobacillus crispatus. Internalization was inhibited by pre-exposure of cells to cytochalasin-D. In addition, the cytoskeletal protein vimentin was upregulated in VK2 cells exposed to G. vaginalis, but there was no change in actin cytoskeletal polymerization/rearrangements or vimentin subcellular relocalization post exposure. Cytoskeletal protein modifications could represent a potential mechanism for G. vaginalis mediated internalization by vaginal epithelial cells. Finally, understanding vaginal bacteria/host interactions will allow us to better understand the underlying mechanisms of BV pathogenesis.     

Identification of antigenic proteins in Trichomonas vaginalis

Trichomoniasis is a sexually transmitted disease due to infection with Trichomonas vaginalis, and it can cause serious consequences for women's health. To study the virulence factors of this pathogen, T. vaginalis surface proteins were investigated using polyclonal antibodies specific to the membrane fractions of T. vaginalis. The T. vaginalis expression library was constructed by cloning the cDNA derived from mRNA of T. vaginalis into a phage λ Uni-ZAP XR vector, and then used for immunoscreening with the anti-membrane proteins of T. vaginalis antibodies. The immunoreactive proteins identified included adhesion protein AP65-1, α-actinin, kinesin-associated protein, teneurin, and 2 independent hypothetical proteins. Immunofluorescence assays showed that AP65-1, one of the identified immunogenic clones, is prevalent in the whole body of T. vaginalis. This study led us to identify T. vaginalis proteins which may stimulate immune responses by human cells.     

化脓性链球菌溶血素O活性结构重组蛋白的制备

生物信息分析化脓性链球菌溶血素O(streptolysin O,Slo)蛋白结构表明,Slo蛋白除含有由461氨基酸残基组成的溶血活性结构域Thiol_cytolysin外,在N端还有一跨膜结构域。利用pET101-GENE蛋白表达系统,成功构建出表达具有Slo活性重组蛋白的重组子,采用镍柱亲和层析分离技术,纯化目的蛋白;纯化蛋白SDS-PAGE检测分析表明,重组蛋白与预测的溶血活性结构域的分子量相一致;溶血实验显示,纯化重组蛋白具有溶血活性。以纯化的重组蛋白为免疫原,对大鼠进行4次免疫,所获得免疫血清经 Elisa检测,抗Slo血清效价达到 1 ∶12 800;Western blot检测猪链球菌、马链球菌和化脓性链球菌中的链球菌溶血素结果显示,抗Slo多克隆抗体仅能与化脓性链球菌溶血素O发生反应,表明研究制备的化脓性链球菌溶血素O活性结构重组蛋白抗原具有较好的特异性,所制备的抗原Slo 可用于进一步开发抗链球菌溶血素O(ASO)试剂盒。     

Cryptic domains of a 60 kDa heat shock protein of Helicobacter pylori bound to bovine lactoferrin

Abstract Bovine lactoferrin binds to a 60 kDa heat shock protein of Helicobacter pylori . Binding ability was related to human immunoglobulin G because bovine lactoferrin binding proteins were isolated by extraction of cell surface associated proteins with distilled water, applied on IgG-Sepharose and nickel sulphate chelate affinity chromatography. Binding was demonstrated by Western blot after purified protein was digested with α-chymotrypsin and incubated with peroxidase-labeled bovine lactoferrin. Binding was inhibited by bovine lactoferrin, lactose, rhamnose, galactose, and two iron-containing proteins, ferritin and haptoglobin. Helicobacter pylori binds ferritin and haptoglobin via charge or hydrophobic interactions because this binding was not inhibited by specific and various glycoproteins or carbohydrates. Carbohydrate moieties of bovine lactoferrin molecules seem to be involved in binding because glycoproteins with similar carbohydrate structures strongly inhibited binding. Scatchard plot analysis of the binding of peroxidase-labeled bovine lactoferrin to H. pylori cells yielded a k _d 2.88 × 10⁻⁶ M. In addition, binding of H. pylori cells to bovine lactoferrin was enhanced when bacteria treated with pepsin or α-chymotrypsin after isolation from iron-restricted and iron-containing media.     

从少量培养细胞中同时提取微量蛋白和RNA的方法探讨

为建立一项从少量培养细胞中同时提取RNA和蛋白质的技术 ,向 2～ 3× 10 5细胞中加入 1ml自制RNA提取试剂 ,RNA抽提后剩下的中下两相 ,用异丙醇、盐酸胍和无水乙醇抽提蛋白质 .同时用进口Tripure试剂、经典的异硫氰酸胍 苯酚 氯仿一步抽提RNA法和分子克隆实验手册裂解液制备蛋白质的方法 ,作为对照 .自制试剂提取的总RNA ,18S、2 8S清晰可见 ,2 8S比 18S带亮度强 2～ 3倍 ,带与带之间无拖尾现象 ,5S隐约可见 ,而且成功地进行了Northern印迹、RT PCR分析 ,与经典方法差异不大 ;用此法所提蛋白质 ,经SDS PAGE检测 ,蛋白分离效果很好 ,无杂质 ,且Western印迹检测Giα蛋白 ,可见一条清晰的特异带 ,与常规提取蛋白质 ,结果相似 .从微量细胞中同时提取的RNA和蛋白质 ,得率高、纯度好 ,具有化学完整性和生物学性质     

尼帕病毒融合蛋白、受体结合蛋白的表达及特异性高免血清制备

尼帕病毒膜融合蛋白F和受体结合蛋白G在病毒感染和诱导机体产生保护性免疫中起重要的作用。通过PCR扩增获得尼帕病毒F1和G基因片段(均去掉信号肽和跨膜区),克隆至原核表达载体,IPTG诱导大肠杆菌表达目的蛋白,Western blot表明重组F1、G蛋白与兔抗尼帕病毒血清具有良好的反应原性;同时将F1和G基因克隆至经改造过的杆状病毒表达载体,获得了含有目的基因的重组杆状病毒,接种sf9单层细胞,间接免疫荧光检测表明F1、G蛋白在杆状病毒中正确表达,并与抗尼帕病毒血清具有良好的反应原性。以纯化原核表达的F1、G蛋白免疫兔获得了抗F1和抗G重组蛋白的特异血清,Western blot和间接免疫荧光检测表明所制备的血清具有特异性。试验所表达的抗原和制备的特异血清可用于尼帕病的诊断。     

采用TEV酶法进行整合膜蛋白拓扑学分析

为了研究膜蛋白的跨膜结构,进行拓扑学分析是十分重要的.有许多分析膜蛋白拓扑结构的方法,本文采用烟草蚀斑病毒（TEV）酶特异性切割测试蛋白中跨膜片段的前段或后端所插入的tev识别序列EXXYXQ(S/G),如果TEV酶能够切割,表明该序列位于目标蛋白的细胞 质外.将Tev识别序列ENLYFQG 分别插入到拟南芥整合膜蛋白的的跨膜区域,然后转化进入酿酒酵母中. 消解酶(zymolyase)酶破除酵母的细胞壁后,TEV酶消化球状体,最后通过Western免疫印迹法来分析结果.有关该方法的注意事项在结果中进行了讨论.     

A PSTAIRE CDK-like protein localizes in nuclei and cytoplasm of Physarum polycephalum and functions in the mitosis

CDKs play key roles in controlling cell cycle progression in all eukaryotes. In plants, multiple CDKs are present,among which the best characterized CDKs are PSTAIRE CDKs. In this study, we carried out Western blot,immunoelectron microscopy and antibody treatment with an anti-PSTAIRE monoclonal antibody to explore the subcellular localization and functions of PSTAIRE CDKs in Physarum polycephalum. The results of Western blot and immunoelectron microscopy showed that in P. polycephalum, a PSTAIRE CDK-like protein was 34 kD in molecular weight and located in both nuclei and cytoplasm. In nuclei, the protein was mainly associated with chromosomes and nucleoli. The expression of the PSTAIRE CDK-like protein in both the plasmodia and nuclei showed little fluctuation through the whole cell cycle. When treated with an anti-PSTAIRE monoclonal antibody at early S phase, the cells were arrested in S phase, and the mitotic onset of P. polycephalum was blocked for about 1 h when treated at early G2 phase.Our data indicated that the PSTAIRE CDK-like protein has a direct bearing on the mitosis.     

Use of capillary sodium dodecyl sulfate gel electrophoresis to detect the prion protein extracted from scrapie-infected sheep

Scrapie in sheep and in goats is the prototype of a group of transmissible spongiform encephalopathies (TSE). A feature of these diseases is the accumulation in the brain of rod shaped fibrils that form from an aggregated protein that is a protease-resistant form of a modified normal host cell protein. In this study, we compared SDS gel capillary electrophoresis to conventional SDS-PAGE and Western blot to detect the monomer of this aggregated protein. This prion protein was extracted from the sheep brain by homogenizing the brain stem (10%, w/v) in 0.32 M sucrose and by using a series of ultracentrifugation steps and treatment with sodium lauroyl sarcosine and proteinase K. After the final centrifucation step, the pellet was resuspended in 0.01 M Tris pH 7.4 in a volume equivalent to 0.1 ml/g of brain used. This resuspended pellet was treated with 1% SDS and 5% 2-mercaptoethanol and boiled for 10 min. The analysis was done in a Beckman P/ACE 5500 using a SDS gel capillary (eCap SDS14-200 Beckman capillary). In infected sheep brain samples, but not normal sheep, a major peak at a molecular mass of 16.1 kDa and a minor peak with a leading shoulder were observed. Since the molecular mass determined for this protein was lower than that estimated on Western blot (22.4 kDa), a Ferguson plot was made to determine if there were abberations in the molecular mass determination. After correction, the major peak was estimated to be 19.2 kDa. This has a better correlation with that determined by SDS-PAGE and Western blot. The equivalent amount of brain sample in the capillary was 50 μg. For Western blot, the amount of brain sample was 20 mg. For this assay, this is 100 times less than that needed for Western blot for sheep samples.     

PML（NLS^-）蛋白在NB4细胞及其裸鼠移植瘤中定位的验证

验证中性粒细胞弹性蛋白酶（neutrophil elastase,NE）切割PML—RARa后,PML（NLS-）蛋白的存在和定位。将质粒pCMV-HA—NE电转染NB4细胞,用Westemblot法验证质粒转染成功;提取电转染质粒成功64／NB4细胞的胞浆蛋白,用Westem blot法检测NB4细胞中PML（NLS^-）蛋白的表达;免疫荧光法和激光共聚焦检测电转染质粒成功的NB4细胞中PML（NLS^-）蛋白的表达及定位;同时,建立NB4细胞、K562细胞和电转染质粒成功的NB4细胞裸鼠皮下瘤模型,用Westem blot、免疫组化法检测PML（NLS^-）蛋白在移植瘤组织细胞中的表达与定位。结果表明,westemblot检测电转染质粒pCMV-HA-NE的NB4细胞成功表达NE蛋白：NE酶成功切割PML-RARα,Western blot检测到电转染质粒pCMV-HA-NE的NB4细胞表达PML（NLS^-）蛋白;免疫荧光和激光共聚焦均可检测到电转染质粒成功的NB4细胞中PML（NLS^-）蛋白定位于细胞胞浆：Westem blot和免疫组化法检测到电转染质粒成功的NB4细胞裸鼠移植瘤中的PML（NLS^-）蛋白的表达且定位于细胞胞浆,而NB4和K562细胞裸鼠皮下瘤中PML蛋白主要定位于胞核。综上所述,该文成功将质粒pCMV-HA—NE电转染NB4细胞并用Western blot、免疫荧光、激光共聚焦、免疫组化验证PML（NLS-）蛋白存在于NB4细胞胞浆,这一现象可以为急性早幼粒细胞白血病的临床早期诊断与治疗提供新的依据。     

SARS冠状病毒S蛋白在昆虫细胞中的表达和纯化

导致严重急性呼吸综合征(sevcre acute rcspiratory syndrome,SARS)的元凶是一种新型的冠状病毒(SARS coronavirus,SARS-CoV)。SARS-CoV感染入侵宿主细胞关键的一环是病毒自身的棘突蛋白(spike protein,S-protein)与细胞受体的相互作用,故而S蛋白己成为SARS研究的主要热点。     

The spike protein of severe acute respiratory syndrome (SARS) is cleaved in virus infected Vero-E6 cells

INTRODUCTION The severe acute respiratory syndrome (SARS), causedby SARS-associated coronavirus (SARS-CoV) [1], wasrecently identified as a new clinical entity. It apparentlybegan in Guangdong province of China in November of2002 and has spread to sever…     

Monoclonal antibody recognition and function of a DnaK (HSP70) epitope found in gram-negative bacteria.

The isolation and characterization of a monoclonal antibody (MAb 2G5) specific for the bacterial DnaK (HSP70) protein is described. The 2G5 MAb was initially selected because of its ability to bind to DnaK under denaturing conditions. Isotype analyses indicated that 2G5 was an immunoglobulin G2a. Dose-response Western blot (immunoblot) experiments with purified but unconcentrated 2G5 permitted detection of 10 ng of pure DnaK protein. The DnaK epitope was determined by Western blot analysis of a series of truncated DnaK fragments overproduced in Escherichia coli using 5' and 3' dnaK-deleted expression plasmids. The epitope mapped to a 22-amino-acid region spanning DnaK residues 288 and 310. Phylogenetic distribution of the epitope was examined by Western blot analysis of a wide variety of bacterial species and indicated that the epitope was uniquely present in gram-negative organisms. The proximity of the epitope to the presumed DnaK ATP-binding pocket suggested that MAb binding might inhibit DnaK ATPase activity. In vitro analysis supported this prediction and demonstrated that MAb-mediated inhibition of ATPase activity was antibody specific and occurred at stoichiometric molar ratios of MAb to DnaK. Possible mechanisms to explain the ability of the 2G5 MAb to inhibit DnaK activity are discussed.     

丙型肝炎病毒E1蛋白活化MAPK／ERK信号通路促进肝癌细胞增殖

目的研究丙型肝炎病毒（hepatitisCvirus,HCV）编码蛋白E1的生物学功能。方法分别构建编码HCV重要蛋白E1、E2、NS3、NS5a、NS5b的腺病毒载体Ad—E1、Ad—E2、Ad—NS3、Ad—NS5a、Ad—NS5b;将重组并包装的腺病毒分别感染SMMC-7721细胞,测定感染滴度,通过RT—PCR方法在转录水平鉴定HCVE1、E2、NS3、NS5a、NSSb的表达,用Western印迹在蛋白水平鉴定E1蛋白的表达。腺病毒感染SMMC-7721细胞后,通过细胞增殖实验筛选生物学功能最明显的蛋白。将筛选到的Ad—E1感染SMMC-7721细胞,用MTS、结晶紫、细胞周期实验观察体外过表达E1蛋白对感染细胞增殖的影响;Western印迹检测p-ERK、ERK的表达;RT—PCR检测c—Myc、cyclinD1、c—Jun、c．Fos基因的表达。结果成功扩增了能够编码HCV重要蛋白E1、E2、NS3、NS5a、NS5b的高滴度腺病毒Ad—E1、Ad—E2、Ad—NS3、Ad—NS5a、Ad—NS5b,并且通过RT—PCR方法在转录水平鉴定了目的基因的表达,Western印迹方法在蛋白水平鉴定了E1蚩白的表达。通过细胞计数、MTS、结晶紫实验证实Ad—E1感染组细胞较对照组增殖速度加快,细胞周期显示Ad-E1感染组细胞34．38％处于S期,明显高于Ad—GFP（27．32％）（P〈0．05）对照组;Ad-E1感染绢p-ERK蛋白表达量增高,同时与细胞增殖相关的MAPK／ERK下游基因转录水平上凋。结论体外过表达HCVE1蛋白可以明显促进SMMC-7721细胞的增殖,其促增殖作用可能与MAPK／ERK信号通路的活化相关。