人工锌指核酸酶的设计与表达纯化

设计表达了四个锌指核酸酶,用于切断人基因组中的rRNA基因家族的内部转录间隔序列,造成双链断裂,以此提高针对多位点基因打靶的效率,为后续基因打靶应用于基因治疗研究奠定基础。首先,在人rRNA基因家族ITS1序列中找到两个合适的9 bp长的序列(中间间隔6 bp)为锌指蛋白识别位点,根据识别位点序列每个位点分别设计两个三锌指蛋白。通过设计引物进行重叠延伸PCR得到全长编码锌指蛋白的DNA,分别克隆到表达载体pET-28a（+）,构建重组质粒pET28a-ZFP,转化大肠杆菌RossettaTM（DE3）,实现带组氨酸标签的锌指融合蛋白的表达与纯化。同时,将限制性内切酶Fok I的切割结构域分别与四个锌指蛋白序列采用PCR拼接后克隆到表达载体pET-28a（+）,构建重组质粒pET28a-ZFN,转化到大肠杆菌RossettaTM（DE3）,实现带组氨酸标签的锌指核酸酶融合蛋白的表达并纯化。     

Heterologous Expression and Efficient Secretion of Chitosanase from Microbacterium sp. in Escherichia coli

A recombinant expression vector, pCT7-CHISP6H, was constructed for the secretory expression of mature peptide of chitosanase (mMschito) from Microbacterium sp. OU01. The vector contains several elements, including T7 promoter, signal peptide sequence of mschito, 6 × His-tag sequence and PmaCI restriction enzyme cloning site. In pCT7-CHISP6H, mMschito was fused into signal peptide sequence of mschito gene to construct recombinant plasmid pCT7-CHISP6H-mMschito. The recombinant plasmid was transformed into Escherichia coli BL21(DE3) and then expressed. The recombinant protein was secreted into the Luria–Bertani broth and the chitosanase activity in supernatant of the culture could reach up to 67.56 U/mL. The rmMschito in the broth supernatant was purified using HisTrap™ FF Crude column and the purified rmMschito was shown to be apparent homogeneity by 12 % SDS–PAGE analysis. Detected by 4700 MALDI-TOF–TOF-MS, the molecular weight of the purified rmMschito was 26,758.1875 and it was consistent with the predicted molecular weight. Chitosan (degree of deacetylation of 99 %) was mostly hydrolyzed into chitopentaose, chitotriose, and chitobiose by the purified rmMschito.     

深圳地区粉尘螨Ⅱ类变应原基因的多态性分析及其表达蛋白的变应原性鉴定

粉尘螨Ⅱ类变应原(Der fⅡ)是粉尘螨Dermatophagoides farinae主要变应原之一,可引发Ⅰ型变态反应。从深圳地区挑取活粉尘螨,经形态鉴定后纯培养,提取其总RNA,RT-PCR扩增出Der fⅡ 基因,克隆到pMD18-T载体后测序。通过计算机软件分析该基因的多态性。将该目的基因克隆到pET-His表达载体上得到重组质粒pET-Der fⅡ。工程菌经IPTG诱导培养,表达Der fⅡ目的蛋白,该蛋白主要以包涵体形式存在。重组Der fⅡ蛋白通过6His-tag蛋白纯化系统进行分离、纯化,并进行Western blot检测该重组蛋白与对粉尘螨过敏患者血清中IgE的反应性。结果表明,克隆的5株深圳地区的Der fⅡ 基因与GenBank公布的Der fⅡ(AB195580.1)核苷酸序列同源性为96.8%～99.3%,推导的氨基酸序列同源性为93.8%～98.6%。表达纯化的5种重组Der fⅡ蛋白经Western blot检测,表明都具有良好的变应原性。     

<Emphasis Type="Italic">Lactobacillus acidophilus</Emphasis> as a live vehicle for oral immunization against chicken anemia virus

The AcmA binding domains of Lactococcus lactis were used to display the VP1 protein of chicken anemia virus (CAV) on Lactobacillus acidophilus. One and two repeats of the cell wall binding domain of acmA gene were amplified from L. lactis MG1363 genome and then inserted into co-expression vector, pBudCE4.1. The VP1 gene of CAV was then fused to the acmA sequences and the VP2 gene was cloned into the second MCS of the same vector before transformation into Escherichia coli. The expressed recombinant proteins were purified using a His-tag affinity column and mixed with a culture of L. acidophilus. Whole cell ELISA and immunofluorescence assay showed the binding of the recombinant VP1 protein on the surface of the bacterial cells. The lactobacilli cells carrying the CAV VP1 protein were used to immunize specific pathogen-free chickens through the oral route. A moderate level of neutralizing antibody to CAV was detected in the serum of the immunized chickens. A VP1-specific proliferative response was observed in splenocytes of the chickens after oral immunization. The vaccinated groups also showed increased levels of Th1 cytokines interleukin (IL)-2, IL-12, and IFN-γ. These observations suggest that L. acidophilus can be used in the delivery of vaccines to chickens.     

Simultaneous detection of potato viruses Y and X by DAC-ELISA using polyclonal antibodies raised against fused coat proteins expressed in Escherichia coli

Polyclonal antibodies were raised against the bacterial expressed fused coat proteins (CPs) of Potato virus Y (PVY) and Potato virus X (PVX). Truncated CP sequences of PVY (~246 bp) and PVX (~243 bp) were amplified by PCR, cloned into T&A cloning vector and subsequently mobilized in a protein expression vector pET-28b (+). The recombinant CP was expressed as a fusion protein (~20 kDa) with His-tag and purified from E. coli BL21 (DE3) using His-Bind resin. The specificity of the recombinant protein was confirmed by Western blot using previously made polyclonal antibodies against each virus. Polyclonal antibodies developed against the fused CPs in rabbit detected natural infection of PVY and PVX in potato leaf samples collected from IARI experimental farm, by direct antigen-coated enzyme-linked immunosorbent assay (DAC-ELISA).     

Metal-Binding Activity of the Soluble Recombinant Pig Metallothionein 1A Expressed in Escherichia coli

Full-length cDNA for the pig metallothionein 1A (pMT1A) gene was synthesized based on the pig MT1A gene sequence in Genbank and cloned into the pMD18-T vector. After sequence analysis and structure prediction, the pMT1A gene was cloned into vector pET-32a (+) containing a His-tag. The recombinant pMT1A (rpMT1A) was expressed in a soluble form using Escherichia coli Rosetta? (DE3) plysS cells. Western blotting showed that the purified rpMT1A protein bound an anti-His-tag monoclonal antibody. Further investigation revealed that the rpMT1A protein showed high metal-binding activity with the divalent metal ions copper (Cu²⁺), zinc (Zn²⁺), and cadmium (Cd²⁺).     

Molecular cloning, expression and purification of recombinant soluble mouse endostatin as an anti-angiogenic protein in Escherichia coli

Inhibition of angiogenesis has become a particular interest for treatment of solid tumors. Endostatin, a C-terminal fragment of collagen XVIII, has been reported to exhibit potent inhibitory effect on endothelial cells proliferation, migration and tube formation. In this research, the cDNA library of endostatin was synthesized from mouse liver and inserted into the SacI and SalI enzyme-cutting sites of pUC18 cloning vector. The recombinant vector was transferred into Escherichia coli DH5a and the recombinant clone was selected on LB agar plate plus ampicillin. PCR analysis and DNA sequencing proved the presence of intact endostatin gene in pUC18. The endostatin gene subcloned into pET32a expression vector and the competent bacterial cells of E. coli BL21 were transformed by the vector harboring endostatin gene. In the optimum conditions, expression plasmid was induced with IPTG and recombinant soluble endostatin as a fusion with thioredoxin was purified with Ni–NTA (Ni²⁺-nitrilotriacetate) resin. The results showed that soluble recombinant endostatin as a fusion protein with thioredoxin is a homogenous polypeptide that inhibits angiogenesis (capillary tube formation) in human umbilical vein endothelial cells by 200 ng/ml.     

幽门螺杆菌CagA蛋白N端片段的表达、纯化及其与磷脂酰丝氨酸的亲和力检测

目的:表达和纯化幽门螺杆菌不同菌株的CagA蛋白N端片段,检测其与磷脂酰丝氨酸(PS)的相互作用及亲和力。方法:用PCR方法从幽门螺杆菌3个菌株中扩增出CagA蛋白N端基因,并连接到表达载体pET-28a上;转化大肠杆菌BL21,经IPTG诱导可溶性表达CagA蛋白N端880残基片段;经镍柱亲和纯化后,利用PLOA法检测CagA蛋白与PS的相互作用。结果:构建了3种幽门螺杆菌菌株cagA基因的原核表达质粒pET-28a/cagAJ99、pET-28a/cagA11637及pET-28a/cagASS1,并在大肠杆菌中获得可溶性表达,SDS-PAGE和Western印迹证实得到目标融合蛋白,亲和纯化得到高纯度CagA蛋白。PLOA结果表明,CagA蛋白与PS有明显的相互作用。结论:3种幽门螺杆菌菌株CagA蛋白与PS之间存在相互作用,且不同的CagA与PS有不同的亲和力。     

Isolation of a small DNA fragment carrying the gene for a dihydrofolate reductase from a trimethoprim resistance factor

Summary DNA fragments of the R factor R388 which renders E. coli resistant to trimethoprim by inducing a trimethoprim resistant dihydrofolate reductase (Amyes and Smith, 1974) were inserted into plasmids and screened for the expression of the trimethoprim resistance gene. By means of a two step deletion procedure a 1770 bp EcoRI/BamH1 fragment was isolated which conferred drug resistance and which was found to induce the synthesis of the same dihydrofolate reductase as the parental R factor. Gene dosage experiments indicated that the induction was due to the presence of a dihydrofolate reductase structural gene on the 1770 bp fragment. The gene could be assigned to a segment which was less than 1200 bp long. The 1770 bp fragment and a recombinant plasmid consisting of pSF2124 and part of R388 were mapped with several restriction nucleases. The R factor induced enzyme was partially purified from a strain carrying a multicopy recombinant plasmid into which the 1770 bp fragment was inserted and which induced high levels of dihydrofolate reductase. The enzyme was found to be stable at 100°. Some aspects of the synthesis of dihydrofolate reductase are discussed.Dedicated to Professor Peter Karlson on the occasion of his 60th birthday     

A putative Toll/interleukin‐1 receptor domain protein from Helicobacter pylori is dimeric in solution and interacts with human Toll‐like receptor adaptor myeloid differentiation primary response 88

Helicobacter pylori, an important human pathogen, is capable of causing persistent infection with minimal immune response. The first line of defense during H. pylori infection is through gastric epithelial cells that present TLR, A family of bacterial proteins that share homology with the Toll/IL‐1 receptor (TIR) domain were identified. Bacterial TIR proteins (BTP) mimic human TIR domain proteins and act on myeloid differentiation primary response gene 88 (MyD88) signaling pathways to suppress TLR signaling. H. pylori may also produce a similar protein. A putative H. pylori BTP was found based on sequence homology. The corresponding gene hp1437 was inserted into an expression vector in fusion with an N‐terminal cleavable 6his‐tag. The recombinant protein, 6his‐HP1437, was purified using nickel affinity chromatography with a yield of 8 mg/L culture. Oligomerization of HP1437 was investigated by size‐exclusion chromatography. It was found that HP1437 forms dimers in solution similar to other BTPs. Furthermore, glutathione S‐transferase pull down assays identified an interaction between HP1437 and human TIR domain adaptor MyD88. These findings suggest that HP1437 has the characteristic features of BTPs and may play a direct role in reducing immune response against H. pylori by binding to MyD88 and pave the way for an in‐depth characterization of this putative novel H. pylori virulence factor.     

肠道病毒71型3C蛋白酶在大肠杆菌中的表达及活性研究

本研究利用大肠杆菌表达系统构建肠道病毒71型3C蛋白酶,并进行纯化,对其酶活性进行研究。首先,将3C蛋白酶基因克隆至pET28a载体,在大肠杆菌BL21(DE3)中表达,Ni-NTA柱亲和层析纯化获得3C蛋白酶,经肠激酶酶切去除N端His标签后获得无His标签的3C蛋白酶,再以荧光多肽为底物进行酶活性研究。经过双酶切鉴定和测序证实,重组表达质粒pET28a-3C构建正确,表达的重组3C蛋白酶相对分子质量约22kD;纯化后有无His标签的3C蛋白酶均能催化荧光底物3B-3C,并且两者的酶动力学数据无显著差异,含有His标签的3C蛋白酶Km、Vmax、Kcat分别为22μM、434nM.Min-1、0.0669 Min-1;其最适反应pH为7.0,最佳反应温度为30℃～37℃。本实验成功表达并纯化了重组3C蛋白酶,该酶具有良好的活力,为抗病毒抑制剂、结构蛋白组装、疫苗开发及3C蛋白酶检测方法的研发奠定了基础。     

Expression of the zebrafish β-defensin 3 mature peptide in <Emphasis Type="Italic">Pichia pastoris</Emphasis> and its purification and antibacterial activity

Defensins are abundant in cells and tissues that are involved in host defense against microbial infections. zfDB3 (zebrafish β-defensin 3) is one of 3 copies of defensin β-like genes from zebrafish (Danio rerio). Here we focus on mzfDB3, which is the gene encoding for the zebrafish β-defensin 3 mature peptide. A codon-optimized mzfDB3 gene with a 6×His-tag at the 3′-end was inserted into the pPICZαA expression vector and transformed into Pichia pastoris X-33 cells. The recombinant zebrafish β-defensin 3 mature peptide (rmzfDB3) was induced with 1.0% methanol at 29°C for 72 h and purified by immobilized metal affinity chromatography. MALDI-TOF/TOF analysis confirmed the expected purified product (rmzfDB3, 5.9 kDa). Fermentation supernatant, which contained rmzfDB3, showed antibacterial activity against Grampositive (i.e., Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus) and Gram-negative (i.e., Escherchia coli BL21, Vibrio parahaemolyticus, Salmonella lignieres, and Pseudomonas aeruginosa) bacteria.     

Construction of a dual-tag system for gene expression, protein affinity purification and fusion protein processing

An E. coli vector system was constructed which allows the expression of fusion genes via a l-rhamnose-inducible promotor. The corresponding fusion proteins consist of the maltose-binding protein and a His-tag sequence for affinity purification, the Saccharomyces cerevisiae Smt3 protein for protein processing by proteolytic cleavage and the protein of interest. The Smt3 gene was codon-optimized for expression in E. coli. In a second rhamnose-inducible vector, the S. cerevisiae Ulp1 protease gene for processing Smt3 fusion proteins was fused in the same way to maltose-binding protein and His-tag sequence but without the Smt3 gene. The enhanced green fluorescent protein (eGFP) was used as reporter and protein of interest. Both fusion proteins (MalE-6xHis-Smt3-eGFP and MalE-6xHis-Ulp1) were efficiently produced in E. coli and separately purified by amylose resin. After proteolytic cleavage the products were applied to a Ni-NTA column to remove protease and tags. Pure eGFP protein was obtained in the flow-through of the column in a yield of around 35% of the crude cell extract.     

The thioredoxin system of Helicobacter pylori

This paper describes the purification of thioredoxin reductase (TR) and the characterization, purification, and cloning of thioredoxin (Trx) from Helicobacter pylori. Purification, amino acid sequence analysis, and molecular cloning of the gene encoding thioredoxin revealed that it is a 12-kDa protein which possesses the conserved redox active motif CGPC. The gene encoding Trx was amplified by polymerase chain reaction and inserted into a pET expression vector and used to transform Escherichia coli. Trx was overexpressed by induction with isopropyl-1-thio-beta-D-galactopyranoside as a decahistidine fusion protein and was recovered from the cytoplasm as a soluble and active protein. The redox activity of this protein was characterized using several mammalian proteins of different architecture but all containing disulfide bonds. H. pylori thioredoxin efficiently reduced insulin, human immunoglobulins (IgG/IgA/sIgA), and soluble mucin. Subcellular fractionation analysis of H. pylori revealed that thioredoxin was associated largely with the cytoplasm and inner membrane fractions of the cell in addition to being recovered in the phosphate-buffered saline-soluble fraction of freshly harvested cells. H. pylori TR was purified to homogeneity by chromatography on DEAE-52, Cibacron blue 3GA, and 2',5'-ADP-agarose. Gel filtration revealed that the native TR had a molecular mass of 70 kDa which represented a homodimer composed of two 35-kDa subunits, as determined by SDS-polyacrylamide gel electrophoresis. H. pylori TR (NADPH-dependent) efficiently catalyzed the reduction of 5,5'-dithiobis(nitrobenzoic acid) in the presence of either native or recombinant H. pylori Trx. H. pylori Trx behaved also as a stress response element as broth grown bacteria secreted Trx in response to chemical, biological, and environmental stresses. These observations suggest that Trx may conceivably assist H. pylori in the process of colonization by inducing focal disruption of the oligomeric structure of mucin while rendering host antibody inactive through catalytic reduction.     

A plasmid-based vector system for the cloning and expression of Helicobacter pylori genes encoding outer membrane proteins

Helicobacter pylori produces a number of proteins associated with the outer membrane, including adhesins and the vacuolating cytotoxin. We observed that the functional expression of such proteins is deleterious to Escherichia coli, the host bacterium used for gene cloning. Therefore, a general method was developed for the functional expression of such genes on a shuttle vector in H. pylori, which has been termed SOMPES (Shuttle vector-based Outer Membrane Protein Expression System). The intact, active gene is reconstituted by recombination in H. pylori from partial gene sequences cloned on an E. coli-H. pylori shuttle vector. This system was established in an H. pylori strain carrying a precise, unmarked chromosomal deletion of the vacA gene, which was constructed by adapting the streptomycin sensitivity system to H. pylori. It is based on the expression of the H. pylori rpsL gene as a counterselectable marker in the genetic background of an rpsL mutant. The utility of this approach is demonstrated by the expression of a recombinant gene encoding vacuolating cytotoxin (vacA) and a recombinant gene encoding an adherence-associated outer membrane protein (alpA) in H. pylori. Received: 10 May 1999 / Accepted: 7 July 1999     

幽门螺杆菌热休克蛋白A基因的克隆、表达及免疫原性研究

幽门螺杆菌的感染可诱发人体产生胃炎和消化性溃疡,其组成成分热休克蛋白Ａ（ＨｓｐＡ）可刺激机体产生保护性的免疫反应。用ＰＣＲ方法从幽门螺杆菌的染色体ＤＮＡ上扩增出ＨｓｐＡ基因片段,将其插入原核表达载体ｐＥＴ２２ｂ（＋）中,并在ＢＬ２１（ＤＥ３）大肠杆菌表达。经测序ＨｓｐＡ基因片段有３５４ｂｐ组成,可编码１１８个氨基酸残基的多肽。ＳＤＳＰＡＧＥ和免疫印迹分析检测发现,ＨｓｐＡ基因表达的蛋白质分子量约为１５ｋＤ,并证实该重组蛋白质可以被幽门螺杆菌感染阳性患者的血清所识别,同时将其免疫小鼠可刺激机体产生抗该重组蛋白质的抗体。ＨｓｐＡ有可能作为一种有效的蛋白质疫苗用于幽门螺杆菌感染的预防和治疗。     

Codon Optimization Enhances Protein Expression of Bombyx mori Nucleopolyhedrovirus DNA Polymerase in E. coli

Bombyx mori nucleopolyhedrovirus (BmNPV) is a major viral agent that causes deadly grasserie disease in silkworms, while BmNPV DNA polymerase (BmNPV-pol), encoded by ORF53 gene, plays a central role in viral DNA replication. Efficacy studies of BmNPV-POL are limited because of poor heterologous protein expression in E. coli. Here, we redesigned the BmNPV-pol to preferentially match codon frequencies of E. coli without altering the amino acid sequence. Following de novo synthesis, codon-optimized BmNPV-pol (co-BmNPV-pol) gene was cloned into pET32a and pGEX-4T-2 vector. The expression of co-BmNPV-POL in E. coli was significantly increased when BmNPV-POL was fused with GST protein rather than a His-tag. The co-BmNPV-POL fusion proteins were isolated using GST affinity chromatography and Mono Q iron exchange chromatography. Protein purity and identity were confirmed by western blot and MALDI-TOF analyses. The biological activity of purified proteins was measured on a poly(dA)/oligo(dT) primer/template. The specific polymerasing activity of the recombinant BmNPV-POL was 6,329 units/mg at optimal conditions. Thus, a large amount of purified protein as a soluble form with high activity would provide many benefits for the functional research and application of BmNPV-POL.     

Production of Synthetic Methionine-Free and Synthetic Methionine-Limited Alpha Casein: Protein Foodstuff for Patients with Homocystinuria due to Cystathionine Beta-Synthase Deficiency

The aim of this study was to evaluate the possibility that synthetic forms of methionine-free alpha-casein and methionine-limited alpha casein could be produced by recombinant means to form the basis for developing an industrial-scale process for the provision of a foodstuff suitable for patients with homocystinuria due to cystathionine beta-synthase (CBS) deficiency. As a first step, two forms of alpha casein gene, encoding methionine-free alpha casein (Fcas) or a methionine-limited alpha casein (Mcas), were synthesised and expressed in Escherichia coli. Using the overexpression vector pET28a, both genes were highly expressed in E. coli in soluble form as well as in inclusion bodies. The two recombinant proteins were purified by the one step methods using the fused His-tag and the Ni²⁺column and validated by Western blot analysis. This work paves the way for industrial-scale production of proteins suitable for patients with homocystinuria due to CBS deficiency.     

Characterization and Pathogenicity of the Zinc Metalloprotease EmpA of <Emphasis Type="Italic">Vibrio anguillarum</Emphasis> Expressed in <Emphasis Type="Italic">Escherichia coli</Emphasis>

The extracellular zinc metalloprotease (EmpA) is a putative pathogenic factor involved in the invasive process of the fish pathogen Vibrio anguillarum. It is synthesized as a 611–amino-acid preproprotease. The gene encoding EmpA (empA) has already been cloned and sequenced. In this study, empA was inserted into pET24d(+) and expressed in Escherichia coli BL21(DE3). Recombinant EmpA with His-tag was purified in a single step with a His-binding Ni-affinity column to a purity >95%. In addition, proteolytic activity, cytotoxicity, fish pathogenicity, and solubility of the recombinant protein were determined.