新型小肽疫苗的设计——Ⅰ.多联体生长激素释放抑制因子基因的化学合成、克隆与表达

小分子多肽制备抗体效率很低。我们设计了一种新的制备小肽疫苗的方法——小肽自连疫苗。这种新疫苗无需用其它蛋白质作载体,因此纯度高,单一性强,无其它杂抗原。尤其在需要进行自身免疫时这种疫苗效率较高。根据这种设计,我们合成并克隆了一个多联的生长激素释放抑制因子的基因,经过筛选、鉴定,得到了一个最大为六联体的生长激素释放抑制因子基因。该基因放到大肠杆菌中表达,并做Western检测,得到六联体生长激素释放抑制因子的表达菌株,该菌株的表达产物能与生长激素释放抑制因子的抗体发生免疫反应。     

半合成人肿瘤坏死因子cDNA的构建及其在大肠杆菌中的高表达

本文报道从人基因文库中分离淋巴毒素(LT)基因的同时,克隆了肿瘤坏死因子(TNF)基因,这两个基因相距1.2kb.TNF基因有4个外显子,第4外显子编码TNF成熟蛋白157个氨基酸中的140个.将第4外显子切出一部分,再人工合成编码其余氨基酸的DNA片段,两者连接构成重组的人TNF(rhTNF)cDNA,并克隆在大肠杆菌表达载体中成功地得到表达.5 l罐发酵得菌体约20g/l,以L929为靶细胞测定细胞毒活性为10~6-10~7单位/ml.高压液相色谱仪分离纯化rhTNF,冻干后得白色粉剂.测定了这种rhTNF的氨基端的10个氨基酸序列,证明与天然的人TNF完全相同.纯度约为95％.     

合成的人γ-干扰素cDNA在大肠杆菌的高效表达

合成了人γ-干扰素(IFN-γ)cDNA,其特点是选用了大肠杆菌偏爱密码子。将合成基因克隆到含P_L启动子的不同表达载体中,共获得9种不同的表达质粒,它们的SD与起始密码子ATG间的距离(D)不同,在起始翻译区(TIR)的最小自由生成能△G_(f298)~°不同,故其表达量的差异也很大。其中pLY_4-γ_5表达的IFN_γ的量占菌体总蛋白的60％—80％,为国际上所罕见。表达高的原因是由于选择(D)距离适当,△G_(f298)~°较高,以及选用的密码子较好。采用十分简便迅速纯化IFN-γ的方法分离包涵体可达90％以上纯度,再经一步分子筛柱层析,IFN-γ纯度即可达95％以上,比活约2.0×10~7IU/mg。     

eglinC基因的化学合成与克隆

采用固相亚磷酰胺法合成了ｅｇｌｉｎＣ全基因，该基因全长２２１ｂｐ，包括其结构基因，５＇－端起始密码子ＡＴＧ和３＇－端终止密码子ＴＡＧ，并在基因的５＇－和３＇－分别装上ＥｃｏＲＩ和ＢａｍＨＩ位点．共分１２个片段，采取分段合成，酶促连接成完整的ｅｇｌｉｎＣ基因．合成的基因克隆于Ｍ１３载体，经杂交、检测，筛选出含ｅｇｌｉｎＣ基因的克隆．用双脱氧链终止法测其序列，结果与设计的一致．     

EXPRESSION OF A PARTIAL SYNTHETIC HUMAN TNF cDNA IN E. coli

A recombinant human tumour necrosis factor (rhTNF) cDNA was constructed. The TNF gene was isolated from a human genomic gene library. There are four exons in the TNF gene. The fourth exou codes for 140 amino acids of the TNF matured protein which is composed of 157 amino acids. A major portion of the fourth exon was isolated and then ligated to a synthesized DNA fragment coding for the remaining amino acids. The partial synthetic hTNF (rhTNF) cDNA thus generated was subcloned into a vector and successfully expressed in E. coli. 5-1 fer1entator was used to produce rhTNF. About 20g (wet weight) of bacterial pellet per liter medium and 106—10~7 units of cytotoxicity to L929 cells per milliliter medium were obtained. rhTNF was purified by HPLC and dried with a freeze dryer, rhTNF with a purity of about 95% in the form of white powder was obtained. The sequence of ten amino acids at the amino terminus of the rhTNF was determined. The result showed that it was identical with that of the natural human TNF.     

EXPRESSION OF SYNTHESIZED HIRUDIN GENE IN YEAST

Hirudin is a sort of polypeptides secreted from the salivary gland of medicinal leech. It is of potential importance in medicine. We designed and synthesized the hirudin gene based on the amino acid sequence of hirudin HV2, and expressed it using the yeast alpha factor expression system. The yeast strain stably carrying the hirudin expression plasmid was deduced by mutagenesis. After its cultivation in rich nutritious medium for 36—48 h, the hirudin expression product secreted into the culture fluid was 10—20 ATU/ml. The HPLCpure hirudin product could be obtained through a simpler purification procedure, its N-terminal amino acid sequence was identical with the natural product, and it showed potent anticoagulant and antithrombin activity. About 3000 ATU of pure hirudin witha specific activity of 6600 ATU/mg could be obtained from 500 ml of culture fluid.     

人工合成的水蛭素基因在酵母中的表达

本文按水蛭素HV2的氨基酸序列,设计并合成了水蛭素基因,并在酵母α因子表达系统中表达。通过诱变得到的稳定携带水蛭素表达质粒的酵母菌株,在丰富培养基中培养36—48 h后,可在培养液中测得10—20 ATU/ml的分泌的水蛭素表达产物。经过较简单的纯化步骤,得到HPLC纯的水蛭素,其N-端氨基酸序列与天然产物完全相同,并有强烈的抗凝血和抑制凝血酶的活力。从500 ml培养液中可得到约3000 ATU的纯水蛭素,其比活力为6600 ATU/mg。