离子交换色谱法对大肠杆菌表达的人重组骨形态发生蛋白-7的纯化

带有BMP 7基因的大肠杆菌可以用来高量表达重组的人骨形态发生蛋白 7。升温诱导表达后 ,每升培养液大约可得到菌体湿重 3g ,其中目的蛋白约占菌体总蛋白量的 40 %。裂解离心 ,用低浓度变性剂洗涤初步纯化包涵体 ,上清中无目的蛋白损失 ,目的蛋白纯度提高到 60 %,将包涵体溶解于高浓度变性剂溶液中 ,然后在不同条件下用离子交换色谱法对变性状态下的蛋白质进行纯化 ,绝大部分杂蛋白被除去 ,目的蛋白纯度达 95 %以上 ,改变条件 ,可以减少rhBMP 7损失。并做Westernblot对目的蛋白进行特异性鉴定。     

表达重组人骨形态发生蛋白-7工程菌的发酵及表达产物的纯化

目的:研究表达重组人骨形态发生蛋白-7工程菌的发酵和表达产物的纯化工艺。方法:利用16L发酵罐发酵培养工程菌,设定了溶氧、搅拌速度、诱导时机、补料和培养基pH值等发酵条件;通过包涵体洗涤、离子交换层析法纯化目的蛋白。结果:工程菌目的蛋白质表达量占菌体总蛋白质的30%以上,纯化后目的蛋白的纯度可达98%。结论:建立了大肠杆菌高效表达人骨形态发生蛋白-7的发酵及纯化工艺。     

人睫状神经营养因子的原核表达,纯化及其生物效应

人睫状神经营养因子（ｈＣＮＴＦ）克隆入ｐＢＶ２２０中，在ＤＨ５α菌株中表达，重组蛋白以包含体的形式存在，表达量为菌体总蛋白的５０％左右。经比较发现用２ｍｏｌ／Ｌ脲洗涤包含体可溶解大量可溶性细菌蛋白，且包含体损失较小。在高浓度变性剂条件下进行ｓｅｐｈａｒｃｙｌＳ－２００凝胶过滤，解决了纯化中ｈＣＮＴＦ易聚合的问题，在低浓度变性剂条件下进行ＤＥＡＥ离子交换，有利于蛋白活性的保持。经两步纯化后得到均一性ｈＣＮＴＦ，纯度达９５％以上。在自然状态下使ｈＣＮＴＦ复性。纯化复性后的ｈＣＮＴＦ对无血清培养的鸡胚背根节神经元和脊髓腹角运动神经元有明显的维持存活和促进生长发育的生物效应。     

人呼吸道合胞病毒截短F1重组蛋白包涵体的制备、纯化和复性

目的将前期在大肠埃希杆菌中获得表达的A型人呼吸道合胞病毒兰州分离株截短的F1重组蛋白进行纯化和复性,为后期动物免疫制备抗原。方法 37℃诱导重组菌体p ET-42b-F1J/Rossata,诱导完毕后离心收集菌体,高压破碎菌体并收集包涵体后用不同浓度的Triton X-100(细胞裂解液)洗涤包涵体3次。洗涤的包涵体用8 mol/L尿素进行溶解并用镍离子亲和层析方法进行初步纯化,用阳离子交换层析方法对初步纯化蛋白进行最终的纯化。亲和层析纯化蛋白用3种不同的复性液进行了稀释复性。结果 37℃诱导5 000 m L重组菌p ET-42b-F1J/Rossata共收获37 g湿菌体,经过不同浓度Triton X-100洗涤包涵体后纯度可达75%。包涵体用8 mol/L尿素溶解后经镍离子亲和层析纯化纯度约为40%,再用阳离子交换层析介质SP HP进一步纯化样品后纯度可达90%。纯化蛋白以3种不同的复性液都能得到复性,其中复性液3的复性效果相对较好。结论实验中探索了人呼吸道合胞病毒截短F1重组蛋白包涵体的纯化方法及步骤,为后期的蛋白制备及动物免疫奠定了基础。     

重组人成骨蛋白-1的离子交换及分子排阻色谱法纯化及其复性研究

经发酵大量表达重组人成骨蛋白-1(rhOP-1)。SDS-PAGE发现rhOP-1表达量占细菌总蛋白的35%。菌体经裂解、洗涤后,用8mol/L尿素溶解包涵体,离心后提取目的蛋白。经离子交换色谱法对变性状态下的目的蛋白进行纯化,绝大部分杂蛋白被去除,目的蛋白纯度达93%以上。为进一步提高目的蛋白浓度,采用分子排阻色谱法对目的蛋白进行再次纯化,纯度达98%以上。利用降低尿素梯度的方法对纯化的蛋白进行复性,二聚体的含量在50%以上。Westernblot证明了复性后的目的蛋白以单体和有活性的二聚体的形式存在。     

狂犬病病毒重组免疫毒素的表达及其生物活性鉴定

将狂犬病病毒中和性单链抗体基因克隆入原核表达载体pET-PE40,经酶切鉴定及序列测定,成功构建了重组免疫毒素原核表达载体。IPTG诱导后目的蛋白获得高效表达,SDS-PAGE分析目的蛋白主要以不溶性包涵体的形式存在于菌体中,表达量占菌体总蛋白的32.29％。包涵体蛋白经体外复性及离子交换色谱柱、疏水作用色谱柱、Sephadex G200凝胶过滤层析柱三步纯化后获得纯度大于96％的目的蛋白,间接免疫荧光染色检测表明重组免疫毒素与狂犬病病毒感染细胞具有抗原结合活性,MTT试验显示,重组免疫毒素对狂犬病病毒感染细胞具有明显的杀伤作用,而对正常细胞无杀伤作用。     

人血小板衍生生长因子BB亚型包涵体复性与纯化

目的:优化人血小板衍生生长因子BB亚型(PGDF-BB)包涵体复性方法与纯化条件,获得具有较好生物活性的重组PGDF-BB蛋白。方法:对PGDF-BB包涵体以梯度尿素进行变性,选择最佳包涵体变性浓度;比较不同复性条件下的复性率,稳定PGDF-BB包涵体复性方法;参照该蛋白的理化性质,选择适合PGDF-BB重组蛋白的纯化方法。结果:原核系统内实现了PGDF-BB的高表达;通过优化包涵体复性方法,重组蛋白的包涵体复性率可达40%以上;经过多个纯化方法相结合,PGDF-BB的纯度达到95%。结论:通过实验条件的优化,提高了PGDF-BB包涵体复性率,获得高纯度、高生物活性的重组PGDF-BB蛋白。     

基因工程犬干扰素α的制备及纯化工艺

目的：运用基因工程技术制备高活性的重组犬仪干扰素。方法：用发酵罐大量培养工程菌,经超声破碎菌体获粗制包涵体,用1％ TritonX-100洗涤去除部分杂蛋白后,以8mol／L尿素溶解包涵体,稀释复性并超滤浓缩,用阴离子柱层析法纯化目的蛋白,测定重组犬干扰素d的活性。结果：得到的重组犬干扰素仅的相对分子质量为19×10^3,蛋白含量为0.55mg／mL,纯度95.65％,目的蛋白回收率为13.75％,活性1.78×10^7U／mL,比活性3.24×10^7U／mg。结论：制备了高纯度且具有高活性的重组犬α干扰素。     

志贺毒素B(ShT-B)在E.coli中的融合表达及特异性抗体制备

用KpnⅠ、HindⅢ酶切克隆载体pCEM-ShTB_3,然后亚克隆入带有二氢叶酸还原酶(DHFR)的融合表达载体pQE40,构建重组质粒pQE40-ShTB. 转化到E.coli M15中,经IPTG诱导,实现了ShTB-DHFR融合蛋白的高表达,表达量约占菌体总蛋白的21.9％,为包涵体形式。在变性条件下,包涵体蛋白经螯合镍离子的次氨基三乙酸(Ni-NTA)亲和柱一步纯化,得到了纯度为90.5％的重组ShT-B.以纯化的ShTB-DHFR融合蛋白免疫昆明鼠,并结合腹腔注射S180细胞,成功制备了抗ShTB腹水多克隆抗体,效价达1∶1×10~6.间接ELISA和Western印迹结果表明,抗ShT-B多抗与重组蛋白和天然ShT均有特异性结合。本试验结果为毒素检测方法的研究奠定了基础。     

重组人RGD-sTRAIL的表达、纯化及抗肿瘤活性研究

利用PCR技术构建RGD短肽与人肿瘤坏死因子凋亡配体(胞外区114-281)的融合基因,将该DNA片段克隆到原核表达载体pET-11a中。重组质粒转化大肠杆菌BL21(DE3),IPTG诱导后可表达相对分子质量约为20000的目的蛋白,占菌体蛋白的20％左右,且大多数重组蛋白以不溶的包涵体形式存在。Western印迹表明目的蛋白具有人sTRAIL的抗原性。表达产物经变性、复性、离子交换层析和分子筛等步骤,可以得到纯度大干95％的RGD-sTRAIL重组蛋白。肿瘤细胞体外实验发现,纯化后的RGD-sTRAIL重组蛋白能明显抑制人肺癌细胞A549生长,并呈剂量依赖性。研究结果表明,通过复性,包涵体中的RGD-sTRAIL蛋白得到正确的折叠,并在体外具有杀伤肿瘤细胞的活性,从而为进一步研究体内靶向性杀伤肿瘤细胞奠定了基础。     

Production of the recombinant human bone morphogenetic protein-2 in Escherichia coli and testing of its biological activity in vitro and in vivo

Bone morphogenetic protein-2 (rhBMP-2) represents the osteoinductive protein factor which plays a dominant role in growth and regeneration of a bone tissue. In clinical practice the bone grafting materials on the basis of rhBMP-2 are widely applied; the Russian analogues of similar materials are not produced. The fragment of the bmp2gene coding for a mature protein was cloned in Escherichia coli. The effective overproducing strain of rhBMP-2 was created on a basis of the E. coli BL21 (DE3). The rhBMP-2 production was about 25% of total cell protein. The biologically active dimeric form of rhBMP-2 was obtained by isolation and purification of protein from inclusion bodies with subsequent refolding. The rhBMP-2 sample with more than 80% of the dimeric form was obtained, which is able to interact with specific antibodies to BMP-2. Biological activity of the received rhBMP-2 samples was shown in the in vitro experiments by induction of alkaline phosphatase synthesis in C2C12 and C3H10T1/2 cell cultures. On model of the ectopic osteogenesis it was shown that received rhBMP-2 possesses biological activity in vivo, causing tissue calcification in the place of an injection. The protein activity in vivo depends on way of protein introduction and characteristics of protein sample: rhBMP-2 may be introduced in an acid or basic buffer solution, with or without the carrier. The offered method of rhBMP-2 isolation and purification results in increasing common protein yield as well as the maintenance of biologically active dimeric form in comparison with the analogues described in the literature.     

Optimized procedure for expression and renaturation of recombinant human bone morphogenetic protein-2 at high protein concentrations

A prokaryotic expression system has been used to produce recombinant human bone morphogenetic protein-2 (rhBMP-2). However, low rhBMP-2 yields and protein loss during purification and renaturation are the hurdles in the clinical application. Previous studies have indicated that variables such as temperature, host cell, salt concentration, and culture time affect the final rhBMP-2 yield. The optimization of these conditions in an Escherichia coli culture yielded 28.258 mg of rhBMP-2 per liter of culture. To reduce rhBMP-2 loss during purification and renaturation, we performed purification before renaturation in the prokaryotic expression system instead of using the traditional renaturation-before-purification approach. rhBMP-2 was separated on a Sephacryl S-300 HR column and eluted from a DEAE-Sepharose Fast Flow column. The collected protein was refolded by dialysis with urea buffer, which was followed by dialysis with ultrapure water. The purified rhBMP-2 dimer significantly increased alkaline phosphatase (ALP) activity and osteogenic activity in the femoral muscle and showed the same level of bone-forming activity as natural BMP-2. This optimized procedure for expression and renaturation of rhBMP-2 has potential clinical applications.     

Optimized procedure for renaturation of recombinant human bone morphogenetic protein-2 at high protein concentration

The human gene encoding the mature form of bone morphogenetic protein-2 (hBMP-2), a dimeric disulfide-bonded protein of the cystine knot growth factor family, was expressed in recombinant Escherichia coli using a temperature-inducible expression system. The recombinant protein was produced in the form of cytoplasmic inclusion bodies and the effect of different variables on the renaturation of rhBMP-2 was investigated. In particular, variables such as pH, redox conditions, protein concentration, temperature, the presence of different types of aggregation suppressors, and host cell contaminants were studied with respect to their effect on aggregation during refolding and on the final renaturation yield of rhBMP-2. It is shown that the renaturation yield is particularly sensitive to pH, temperature, protein concentration, and the presence of aggregation suppressors. In contrast, little effect of the redox conditions and the ionic strength on the renaturation yield was observed, as equal yields were obtained in a broad range of reduced to oxidized glutathione ratios and concentrations of NaCl, respectively. The aggregation suppressor 2-(cyclohexylamino)ethanesulfonic acid (CHES) proved to be superior with respect to the final renaturation yield, although, in comparison to the more common arginine, it was less efficient in preventing aggregation of rhBMP-2 during refolding. Detergent washing of inclusion bodies was sufficient, as further purification of rhBMP-2 prior to refolding was without effect on the final renaturation yield. An increase in the concentration of renatured rhBMP-2 was achieved by a pulsed refolding procedure by which up to a total amount of 2.1 mg mL(-1) rhBMP-2 could be transferred in seven pulses into the renaturation buffer with an overall refolding yield of 38%, corresponding to 0.8 mg mL(-1) renatured dimeric rhBMP-2. Furthermore, a simplified purification procedure is presented that also includes freeze-drying for long-term storage of biologically active rhBMP-2. Finally, it is shown that the appearance of rhBMP-2 variants could be avoided by using a host strain overexpressing rare codon tRNAs.     

Expression and purification of recombinant human bone morphogenetic protein-7 (rhBMP-7) in <Emphasis Type="Italic">Bacillus subtilis</Emphasis>

The polypeptide representing the mature part of human bone morphogenetic protein-7 (BMP-7) was cloned and efficiently expressed in Bacillus subtilis. Recombinant B. subtilis had a clear band for rhBMP-7, a homodimeric protein with an apparent molecular weight of 15.4 kDa and produced 350 pg rhBMP-7/mL of culture medium. The extracellular and intracellular rhBMP-7 was purified in two steps using a fast performance liquid chromatography (FPLC) system with an ion-exchange column and a gel filtration column. The extracellular rhBMP-7 had a purity of 57.1% and a yield of 58.8%, while the purity of the intracellular rhBMP-7 was 36.2% with a yield of 51.4%. The rhBMP-7 produced in this work also stimulated alkaline phosphatase (ALP) activity in a dose-dependent manner, i.e. 2.5- and 8.9-fold at 100 and 300 ng rhBMP-7/mL, respectively, and showed intact biological activity.     

重组人骨形态发生蛋白-6的表达、纯化及其活性分析

利用RT-PCR从人胎盘组织中获取BMP-6成熟肽的cDNA 片段,并克隆到表达载体pET-15b中, 构建hBMP_6成熟肽的非融合蛋白表达质粒pET-BMP6,转化E.coli BL21（DE3）。IPTG 诱导4h后,工程菌高表达rhBMP-6成熟肽,在SDS-PAGE上出现预期的新蛋白带(≈15kD), 约占菌体总蛋白的10%,表达产物以包涵体形式存在。分离和纯化的包涵体溶解于8 mol/L尿素,在变性溶解状态下经阳离子交换层析,得到目的蛋白纯度达95%以上。再经稀释复性后,约80%的rhBMP-6形成同源二聚体。体外活性分析结果显示：rhBMP-6可以提高C3H10T1/2 细胞碱性磷酸酶活性及促进I型胶原、Osterix（Osx）和骨钙素（Osteocalcin）等成骨细胞表型转化标记基因mRNA的表达,证明制备的rhBMP_6具有诱导非骨源性细胞分化成为成骨细胞的作用。     

EXPRESSION AND PURIFICATION OF RECOMBINANT HUMAN BONE MORPHOGENETIC PROTEIN-7 IN Escherichia coli

Bone morphogenetic protein-7 (BMP-7) is a multifunctional cytokine of the transforming growth factor β superfamily, which induces bone formation and plays an important role during bone tissue repair and embryonic development. In this study, human BMP-7 (hBMP-7) cDNA was cloned and expressed in Escherichia coli, and its yield was approximately 30% of the total bacterial protein. After the bacteria were lysed by ultrasonication and repeated washing, inclusion bodies were extracted and dissolved using a high-strength denaturant. The monomer of rhBMP-7 was purified by ion-exchange chromatography, and the purity coefficient was approximately 96%. The protein was renatured with refolding buffers at different pH values. The renatured rhBMP-7 dimer protein in this study increased the alkaline phosphatase activity of NIH3T3 cells. This study may be helpful for the in vitro production and biomedical application of rhBMP-7 protein expressed in an E. coli expression system.     

Refolding and two-step purification by hydrophobic interaction chromatography of recombinant human bone morphogenetic protein-2 from Escherichia coli

To renature the inactive rhBMP-2 which overexpressed in Escherichia coli, post-expression treatments including inclusion bodies solubilization and in vitro refolding were systematically investigated. An optimized refolding process was established from screening and successfully scaled up with yield greater than 70%. Then, hydrophobic interaction chromatography (HIC) was adopted as two consecutive stages to separate the active rhBMP-2 homodimer from refolding mixture. Aiding additive N,N-dimethylformamide (DMF) was found to enhance the resolution of rhBMP-2 homodimer most effectively. The rhBMP-2 homodimer was purified to homogeneity through two HIC separations at different salt contents, the purified rhBMP-2 homodimer was fully bioactive and had equivalent biological activity to rhBMP-2 produced from Chinese hamster ovary cell (CHO). Under the optimal refolding and purification conditions, 80 mg rhBMP-2 homodimer with high purity could be obtained from 1 g wet weight of inclusion bodies. Finally, this efficient refolding and purification procedure was successfully scaled up in the pilot pharmaceutical plant.     

Effect of a freeze-dried CMC/PLGA microsphere matrix of rhBMP-2 on bone healing

The hypothesis of this research was that implants of poly(lactide-co-glycolide) (PLGA) microspheres loaded with bone morphogenetic protein-2 (rhBMP-2) and distributed in a freeze-dried carboxymethylcellulose (CMC) matrix would produce more new bone than would matrix implants of non-protein-loaded microspheres or matrix implants of only CMC. To test this hypothesis it was necessary to fashion microsphere-loaded CMC implants that were simple to insert, fit precisely into a defect, and would not elicit swelling. Microspheres were produced via a water-in-oil-in-water double-emulsion system and were loaded with rhBMP-2 by soaking them in a buffered solution of the protein at a concentration of 5.4 mg protein per gram of PLGA. Following recovery of the loaded microspheres by lyophilization matrices for implantation were prepared by lyophilizing a suspension of the microspheres in 2% CMC in flat-bottom tissue culture plates. Similar matrices were made with 2% CMC and with 2% CMC containing blank microspheres. A full-thickness calvarial defect model in New Zealand white rabbits was used to assess bone growth. Implants fit the defect well allowing for direct application. Six weeks postsurgery, defects were collected and processed for undecalcified histology. In vitro, 60% of the loaded rhBMP-2 released from devices or microspheres in 5 to 7 days. With the unembedded microspheres releasing faster than those embedded in CMC In vivo. the rhBMP-2 microspheres greatly enhanced bone healing, whereas nonloaded PLGA microspheres in the CMC implants had little effect. The results showed that a lyophilized device of rhBMP-2 PLGA microspheres in CMC was an effective implantable protein-delivery system for the use in bone repair. Published: October 7. 2001.     

Expression,purification, and refolding of a recombinant human bone morphogenetic protein 2 in vitro

In this work, the recombinant human bone morphogenetic protein 2 (rhBMP-2) gene was cloned from MG-63 cells by RT-PCR, and the protein was expressed in Escherichia coli expression system, purified by Ni–NTA column under denaturing conditions and refolded at 4 °C by urea gradient dialysis. We found that the protein refolding yield was increased with the increase of pH value from pH 6.0 to pH 9.0. The yield was 42% and 96% at pH 7.4 and pH 9.0, respectively, while that at pH 6.0 was only 3.4%. The cell culture results showed that the rhBMP-2 refolded at pH 7.4 urea gradient dialysis had higher biological activity for MG-63 cell proliferation and differentiation than that refolded at pH 9.0 since pH 7.4 is closer to the conditions in vivo leading to the formation of dimers through the interchain disulfide bond. Moreover, the biological activity for MG-63 was promoted with the increase of rhBMP-2 concentration in the cell culture medium. This work may be important for the in vitro production and biomedical application of rhBMP-2 protein.