以肽脱甲酰基酶为靶点的抗结核药物高通量筛选模型的建立和应用

目的建立以肽脱甲酰基酶(PDF)为靶点的抗结核药物高通量筛选模型,应用该模型筛选得到活性微生物发酵液粗提物样品。方法以结核分枝杆菌H37Rv基因组为模板,扩增肽脱甲酰基酶的基因片段def,构建表达载体pET-28a-def,表达并纯化结核分枝杆菌PDF酶;基于PDF水解三肽底物for-Met-Ala-Ser释放出游离NH2,而游离NH2可与荧光胺反应产生荧光的原理,利用测定所产生荧光值的方法,建立高通量药物筛选模型;使用该模型对12400个微生物发酵液粗提物样品进行筛选,同时以耻垢分枝杆菌为检定菌,平板纸片法检测样品的抗菌活性,并检测所得阳性样品的细胞毒性。结果成功构建了表达载体pET-28a-def;所建立的模型稳定可行,可用于以肽脱甲酰基酶为靶点的抗结核药物的高通量筛选;用该模型对12400个微生物发酵液粗提物样品进行筛选,最终得到8个对肽脱甲酰基酶抑制活性和抗耻垢分枝杆菌活性均较好的阳性样品,阳性率0.06%;其中5个样品的细胞毒性较小。结论建立了灵敏度好、稳定性高的结核分枝杆菌肽脱甲酰基酶抑制剂高通量药物筛选模型,应用该模型所得到的阳性样品具有进一步深入研究的意义。     

表达幽门螺杆菌NAP基因的减毒沙门菌疫苗株的建立

目的：建立表达幽门螺杆菌(H．pylori)中性粒细胞活化蛋白(Hp—NAP)的减毒沙门菌疫苗株。方法：用PCR扩增Hp—NAP基因，并克隆至原核表达质粒pTrc99A中，经PCR及酶切鉴定后测定其基因序列，并与GenBank中相关序列的同源性进行比较。以重组质粒pTrc99A—NAP转化减毒伤寒沙门菌SL3261，培养后筛选阳性菌落，抽提质粒进行PCR及酶切鉴定。表达的Hp—NAP蛋白用SDS—PAGE进行鉴定，用薄层扫描分析蛋白含量。结果：核苷酸序列测定及同源性分析证实，克隆的Hp—NAP基因与GenBank中相关序列的同源性为98％(397／402)，氨基酸序列的同源性为98％(131／133)。以重组质粒pTrc99A—NAP转化的减毒沙门菌，可表达Mr约15000的Hp—NAP蛋白，表达量约占菌体蛋白量的37．5％。结论：建立了可表达Hp—NAP基因的减毒鼠伤寒沙门疫苗株，为进一步研制Hp口眼疫苗奠定了基础。     

人生长分化因子-5完整成熟肽基因的克隆

目的：克隆人生长分化因子-5(hGDF-5)完整成熟肽基因。方法：根据Genbank中hGDF-5的序列化学合成两条引物，从人胎儿软骨组织提取总RNA，通过反转录聚合酶链式反应(RT—PCR)得到hGDF-5完整成熟肽基因。将所得基因片段插入克隆载体pMD18-T并转化大肠杆菌DH5α，提取重组质粒，酶切鉴定并测序。结果：DNA琼脂糖凝胶电泳显示：PCR产物为一长约380bp的带，阳性克隆质粒经双酶切可切出约380bp的片段。全自动DNA测序表明与Genbank中的序列完全相符。结论：通过反转录聚合酶链式反应从人胎儿软骨组织中成功克隆出人GDF-5完整成熟肽基因，基因序列完全正确。     

UreA/KatA双价减毒沙门菌疫苗株抗幽门螺杆菌的免疫保护作用

目的探讨由2种幽门螺杆菌(Hp)抗原组合的双价疫苗在防治Hp感染中的作用以及减毒鼠伤寒沙门菌作为传递Hp抗原的活疫苗载体的可行性.方法PCR技术扩增尿素酶A亚单位(ureA)和过氧化氢酶(katA)基因片段,构建表达UreA/KatA融合蛋白的重组质粒,重组质粒宿主菌经IPTG诱导,用SDS-PAGE和Westernblot分析UreA/KatA的表达情况.将该重组质粒转入减毒鼠伤寒沙门菌SL3261株中构建重组口服活疫苗株,经口服免疫C57BL/6小鼠,再用Hp悉尼株进行攻击,用快速尿素酶试验和细菌定量培养对胃粘膜中Hp的定植及生长情况进行观察.结果SDS-PAGE电泳图上显示1条相对分子质量(Mr)约108×103的新生蛋白带,占细菌总蛋白的5%,并能与抗GST抗体发生特异性反应.动物实验结果显示,经UreA/KatA双价疫苗免疫的小鼠能有效防御Hp的感染.结论表达UreA/KatA融合蛋白的双价减毒沙门菌疫苗株能诱导抗Hp保护性免疫反应,有望在Hp感染及其相关性疾病的防治中发挥积极作用.     

BirA酶基因表达载体的构建、原核表达及表达产物的活性鉴定

目的:构建生物素-蛋白连接酶(BirA酶)基因的表达载体,并在大肠杆菌BL-21(DE3)中表达具有生物学活性的BirA酶。方法:用PCR法扩增BirA酶基因。将PCR产物克隆入pGEX-4T-2中构建BirA酶-GST融合蛋白基因的重组表达载体pGEX-BirA。经测序验证后,在大肠杆菌BL-21(DE3)中诱导表达,表达产物采用谷胱苷肽-琼脂糖层析柱进行纯化。以带有生物素酶底物肽(BirAsubstratepeptide,BSP)的HLA-A2-肽复合物为底物,用ELISA和Westernblot鉴定表达产物的生物素化活性。结果:构建了pGEX-BirA原核表达质粒,并在大肠杆菌BL-21(DE3)中诱导表达Mr为61300的BirA酶-GST融合蛋白,表达产物经谷胱苷肽-琼脂糖层析柱纯化后,得到N端带有GST标签的BirA酶蛋白。ELISA和Westernblot的结果显示,表达产物能使HLA-A2-肽复合物生物素化。结论:成功地制备了具有生物学活性的Bi-rA酶,为研究蛋白质分子的相互作用提供了有效的制剂。     

人KLK1和EGFP双顺反子重组腺病毒构建及其在血管平滑肌细胞中的表达

目的：构建携EGFP为报告基因和人组织激肽释放酶1(hKLK1)基因双顺反子的重组腺病毒（Ad-hKLK1-IRES-EGFP）,并观察在自发性高血压大鼠（SHR）血管平滑肌细胞（VSMCs）中的表达变化。方法:通过双酶切质粒pBluescritII KS-hKLK1，将hKLK1基因定向克隆至带有IRES-EGFP的腺病毒穿梭质粒pDC316中，构建成重组穿梭质粒 ，将其与腺病毒骨架质粒BHGloxE1，3Cre共转染293A细胞，经包装并获得重组腺病毒，用PCR、酶切及测序方法对其进行鉴定，测定病毒滴度；用重组腺病毒感染VSMCs，用荧光显微镜下观察到的绿色荧光来测定感染率，用RT－PCR和Western blotting法测定hKLK1基因在VSMCs中的表达。结果:PCR、酶切和测序表明携EGFP的重组穿梭质粒pDC316-hKLK1-IRES-EGFP构建正确，并与骨架质粒在293A细胞中成功包装出重组腺病毒Ad-hKLK1-IRES-EGFP，其滴度为4.5×10¹¹/L。重组腺病毒感染VSMCs后，在荧光显微镜下观察到明亮绿色荧光蛋白表达，感染率高达90％以上，可检测到hKLK1基因的mRNA及蛋白表达，并与感染时间(1 d-7 d) 有显著依赖关系，峰值感染复数为100 MOI。结论:成功构建并包装了携EGFP和hKLK1基因的双顺反子重组腺病毒载体系统Ad-hKLK1-IRES-EGFP；感染VSMCs可检测到基因hKLK1和EGFP的独立共同高表达，该系统为一直观、安全、高效的基因转移系统。     

幽门螺杆菌尿毒酶B基因的克隆与高效表达

目的 克隆并表达幽门螺杆菌尿素酶B基因。方法 提取幽门螺杆菌染色体DNA，用PCR方法扩增尿素酶B基因。将其克隆至表达载体pQE30,转化大肠杆菌M15，IPTG诱导表达。结果 分离得到了1．7kb的 ureB基因片段，并在大肠杆菌中实现了该基因的高效表达。在37℃诱导表达4h后，表达产物约占细菌总蛋白的34．0％，表达以可溶性蛋白和包涵体两种形式存在，其中主要是包涵体的形式，目的蛋白占不溶性蛋白的55．8％。结论 幽门螺杆菌ureB基因的克隆与表达为Hp疫苗的研制打下了基础。     

大肠杆菌肽脱甲酰基酶的表达、纯化及活性检测

肽脱甲酰基酶(peptide deformylase,PDF)是原核生物生长、代谢、繁殖必不可少的关键酶,而在人类和其他哺乳动物中不发挥明显作用,因而被视为新一代广谱抗生素药物筛选的理想靶点.最早被发现并进行研究的是大肠杆菌的PDF,但其体外活性非常低且不稳定,20世纪90年代以来人们一直在对不同金属离子形式的PDF进行研究,以获得既稳定活性又高的PDF.     

幽门螺杆菌omp11基因的克隆及序列分析

目的　对幽门螺杆菌 (Helicobacterpylori,Hp)郑州分离株MEL Hp2 7和NCTC116 37株外膜蛋白基因 (omp11)进行克隆和测序 ;确定不同Hp菌株omp11基因序列的变异性 ,并对该基因编码多肽的化学及免疫学特性进行预测 ,为幽门螺杆菌疫苗抗原的筛选提供数据。方法　提取Hp染色体DNA ,用自行设计的PCR引物 ,从染色体DNA上扩增出omp11基因 ,将其克隆到载体pNEB193中 ,用重组质粒转化大肠杆菌 (E .coliJM10 9)。对重组质粒进行酶切鉴定 ,对插入的omp11基因片段进行测序 ,应用生物信息学软件Omiga2 .0、GeneDoc2 .3和GenBank、Swiss port数据库对 4个Hp菌株 (MEL Hp2 7、NCTC116 37、2 6 6 95、J99)的omp11基因序列进行同源性分析 ,并对该基因编码多肽的主要化学特征和抗原结构域进行预测。结果　MEL Hp2 7和NCTC116 37株omp11基因的核苷酸序列长度均为5 6 1bp ,不同菌株间核苷酸序列的同源性为 96 .6 %～ 98.0 % ,与国内的MEL Hp2 7株同源性最高的菌株是NCTC116 37,二者的同源性为 97.9%。 4株Hpomp11基因编码的氨基酸序列长度均为 186aa ,不同菌株间氨基酸序列的同源性为 98.9%～ 10 0 % ,与MEL Hp2 7株同源性最高的菌株是 2 6 6 95 ,二者的同源性为 99.5 %。预测HpMEL Hp2 7omp11基因编码多肽的相对分子质量 (Mr)     

人BDNF成熟肽基因克隆及序列分析(英文)

为研究人脑源性神经营养因子在大肠杆菌中的表达及其在治疗 Alzheimer病中的作用 ,本文作者等克隆了其成熟肽基因并进行了序列分析。提取健康成人末梢血白细胞基因组 DNA作为模板 ,应用 PCR技术扩增人脑源性神经营养因子成熟肽基因片段 ,并将其插入 p GEM-T质粒。限制性内切酶鉴定重组质粒并进行序列测定和分析。与 Gen Bank提供的已知序列(M61181)比较 ,所克隆的人脑源性神经营养因子成熟肽基因片段长 3 5 7bp,序列完全相同。人脑源性神经营养因子成熟肽基因的克隆 ,为其在原核细胞中的表达、抗体的制备及神经系统疾病的治疗奠定了基础     

Identification by PCR of Helicobacter pylori in subgingival plaque of adult periodontitis patients.

The PCR was used to detect the presence of Helicobacter pylori in subgingival plaque samples from patients with adult periodontitis. Primers based upon the 16S ribosomal RNA (rRNA) gene sequence of H. pylori were used in a single round of PCR to amplify a 295-bp DNA fragment and the identity of the amplified products was confirmed by Southern blot hybridisation to a digoxigenin-labelled H. pylori probe. Further confirmation of product identity was obtained by DNA sequencing of a proportion of the amplified products. The assay was demonstrated to be specific for H. pylori with a lower limit of detection of 100 fg of bacterial genomic DNA. In all, 73 samples from 29 patients were analysed, of which 24 (33%) were H. pylori-positive by PCR; the proportion of patients carrying H. pylori in at least one sampled site was 38% (11 of 29). This is the first study to demonstrate the presence of H. pylori in the subgingival plaque of patients with adult periodontitis and indicates that, in this patient group at least, subgingival plaque may be a reservoir for H. pylori infection.     

Introduction of unmarked mutations in the Helicobacter pylori vacA gene with a sucrose sensitivity marker.

Research on Helicobacter pylori has been hindered by the lack of useful genetic tools. Using the sacB gene of Bacillus subtilis, we developed a sucrose-based counterselection system that allows introduction of unmarked mutations in H. pylori. A kan-sacB cassette, consisting of the sacB gene expressed from the H. pylori flagellin promoter and the kanamycin resistance module, was introduced by homologous recombination into a target H. pylori gene. The resultant strains were sucrose sensitive and kanamycin resistant. Following transformation with a mutated allele, growth in sucrose-containing medium allowed the selection of strains that had lost the kan-sacB module and had integrated the unmarked allele. We have used this cassette to perform a site-directed modification of two histidine residues encoded by the vacA gene in a two-step procedure. This system should prove useful in the site-directed mutagenesis of H. pylori genes.     

Development of two PCR-based techniques for detecting helical and coccoid forms of Helicobacter pylori

The primary mode of transmission of Helicobacter pylori, a human pathogen carried by more than half the population worldwide, is still unresolved. Some epidemiological data suggest water as a possible transmission route. H. pylori in the environment transforms into a nonculturable, coccoid form, which frequently results in the failure to detect this bacterium in environmental samples by conventional culture techniques. To overcome limitations associated with culturing, molecular approaches based on DNA amplification by PCR have been developed and used for the detection of H. pylori in clinical and environmental samples. Our results showed the glmM gene as the most promising target for detection of H. pylori by PCR amplification. Under optimal amplification conditions, glmM-specific primers generated PCR-amplified products that were specific for H. pylori and some other Helicobacter species. Genome sequence analysis revealed the existence of a conserved region linked to a hypervariable region upstream of the 16S rRNA gene of H. pylori. Selective PCR primer sets targeting this sequence were evaluated for the specific detection of H. pylori. One primer set, Cluster2 and B1J99, were shown to be highly specific for H. pylori strains and did not produce any PCR products when other Helicobacter species and other bacterial species were analyzed. In tests with 32 strains of H. pylori, 6 strains of other Helicobacter species, 8 strains of Campylobacter jejuni, and 21 strains belonging to different genera, the primers for glmM were selective for the Helicobacter genus and the primers containing the region flanking the 16S rRNA gene were selective for H. pylori species only. The combination of two sensitive PCR-based methods, one targeting the glmM gene and the other targeting a hypervariable flanking region upstream of the 16S rRNA gene, are complementary to each other. Whereas the glmM-specific primers provide a rapid, sensitive presumptive assay for the presence of H. pylori and closely related Helicobacter spp., the primers for sequences flanking the 16S rRNA gene can confirm the presence of H. pylori and locate the potential source of this bacterium.     

Mutation of the cytotoxin-associated cagA gene does not affect the vacuolating cytotoxin activity of Helicobacter pylori.

Helicobacter pylori now is recognized as an etiological agent in chronic superficial gastritis and peptic ulcer disease. Although only about 60% of H. pylori isolates produce an immunodominant 128-kDa antigen (CagA; cytotoxin-associated gene product), virtually all H. pylori-infected patients with duodenal ulceration develop a serologic response to the 128-kDa protein, which suggests an association of this gene with ulceration. The cloned cagA gene from H. pylori 84-183 was disrupted by insertion of a kanamycin resistance gene, and this inactivated cagA construct was introduced into H. pylori 84-183 by electrotransformation. Southern hybridization of kanamycin-resistant H. pylori transformants demonstrated that the wild-type cagA gene had been disrupted by insertion of the kanamycin cassette, and immunoblot analysis showed that the mutant strains no longer produced the 128-kDa CagA protein. Similar results were obtained when the cagA mutation was introduced by natural transformation into H. pylori 60190, a high-level toxin-producing strain. The cagA-negative H. pylori strains showed cytotoxin, urease, and phospholipase C activities, C3 binding and adherence similar to those of the isogenic wild-type strains. These findings demonstrate that the cagA gene product does not affect the vacuolating cytotoxin activity of H. pylori.     

Comparison of PCR-based restriction length polymorphism analysis of urease genes with rRNA gene profiling for monitoring Helicobacter pylori infections in patients on triple therapy.

Multiple isolates of Helicobacter pylori from antral biopsies of nine patients were examined by DNA fingerprinting. Analysis of rRNA gene patterns and HaeIII restriction fragment length polymorphism of PCR-amplified urease genes were compared and used to study colonization before and after failed triple therapy. H. pylori isolates from a single biopsy shared the same HaeIII DNA fingerprint regardless of the isolation method (plate or broth). DNA pattern types of paired strains of H. pylori were distinct between patients and were not grossly affected by treatment except for one patient with an altered strain type. H. pylori infections were generally associated with several subpopulations of strains, evident from the subtypic variation before and after treatment, detectable by both DNA fingerprinting methods. The urease gene patterns also provided evidence that some cultures of H. pylori probably contained a mixture of genomic subtypes. The study suggests that triple therapy has the effect either of inducing minor genomic variations or of changing the proportions of different subtypes of H. pylori. It was concluded that urease gene profiling provides a simple yet reliable method of establishing whether treatment failures are attributable to incomplete eradication of H. pylori.     

Immunological and molecular characterization of Helicobacter felis urease.

Urease activity has recently been shown to be an important virulence determinant for Helicobacter pylori, allowing it to survive the low pH of the stomach during colonization. Experimental murine infection with Helicobacter felis is now being used as a model for H. pylori infection to study the effects of vaccines, antibiotics, and urease inhibitors on colonization. However, little information comparing the ureases of H. felis and H. pylori is available. Urease was partially purified from the cell surface of H. felis ATCC 49179 by A-5M agarose chromatography, resulting in an eightfold increase in specific activity over that of crude urease. The apparent Km for urea for the partially purified urease was 0.4 mM, and the enzyme was inhibited in a competitive manner by flurofamide (50% inhibitory concentration = 0.12 microM). Antiserum to whole cells of H. pylori recognized both H. pylori and H. felis urease B subunits. Antiserum raised against H. felis whole cells recognized the large and small autologous urease subunits and the cpn60 heat shock molecule in both H. felis and H. pylori. However, this antiserum showed only a weak reaction with the B subunit of H. pylori urease. Two oligomeric DNA sequences were used as probes to evaluate the relatedness of H. felis and H. pylori urease gene sequences. One 30-mer from the ureA sequence, which had been shown previously to be specific for H. pylori, failed to hybridize to H. felis genomic DNA. A probe to the putative coding sequence for the active site of the H. pylori ureB subunit hybridized at low intensity to a 2.8-kb fragment of BamHI-HindIII-digested H. felis DNA, suggesting that the sequences were homologous but not identical, a result confirmed from the recently published sequences of ureA and ureB from H. felis.