蝎镇痛活性肽AS的一个二硫键对镇痛活性的影响

目的研究蝎镇痛活性肽AS中二硫键C12-C62对其生物活性的影响。方法利用一步聚合酶链式反应(polymerase chain reaction,PCR)分别用Ser替代蝎镇痛活性肽AS中第12位、第62位及第12位和第62位的Cys,从而构建其3个突变体。采用金属离子螯合亲和层析方法对表达突变体蛋白进行纯化。采用小鼠扭体法测定3个突变体的镇痛活性。结果构建了3个突变体质粒,在BL21(DE3)中实现了可溶性表达。采用金属离子螯合层析方法获得了电泳纯样品。其镇痛活性明显低于Bmk AS(P<0.01)。结论3个突变体与rBmK AS镇痛活性有明显差异,二硫键C12-C62与蝎毒镇痛活性密切相关。     

蝎镇痛抗肿瘤缬精甘肽的两个氨基酸残基对镇痛活性的影响

目的研究蝎镇痛抗肿瘤缬精甘肽(analgesic-antitumor peptide,AGAP)中2个氨基酸残基对其镇痛活性的影响。方法利用已构建成功的2个突变体W38G和R58D,采用金属离子螯合亲和层析和阳离子交换层析方法对突变体蛋白进行纯化。采用小鼠醋酸扭体法测定两个突变体的镇痛活性。结果在大肠杆菌BL21(DE3)中实现了可溶性表达。采用金属离子螯合层析和阳离子交换层析方法获得了电泳纯样品。突变体W38G镇痛活性与未突变重组蛋白(recombinant analgesic-antitumor peptide from Buthus martensii Karschr,BmK AGAP)相同,突变体R58D镇痛活性降低。结论突变体与rBmK AGAP相比镇痛活性发生变化,说明所选取的突变位点对蝎镇痛抗肿瘤缬精甘肽的镇痛活性具有一定的调节作用。     

镇痛抗肿瘤缬精甘肽BmK AGAP的两对二硫键C16-C36和C22-C46对镇痛活性的影响

目的研究二硫键C16-C36和C22-C46对镇痛抗肿瘤缬精甘肽BmK AGAP镇痛活性的影响。方法使用本实验室已构建成功的2个二硫键双突变体(C16S,C36S)和(C22S,C46S),在大肠杆菌中诱导表达,通过金属离子螯合亲和层析和阳离子交换层析方法对突变体蛋白分离纯化,采用小鼠醋酸扭体法测定2个突变体的镇痛活性,圆二色谱分析BmK AGAP和2个二硫键突变体的二级结构变化差异,利用生物信息学的方法模建BmK AGAP的三维空间结构。结果 a.目的蛋白在大肠杆菌BL21(DE3)中实现了可溶性表达;b.采用金属离子螯合亲和层析和阳离子交换层析方法获得了电泳纯样品;c.2个双突变体(C16S,C36S)和(C22S,C46S)的镇痛活性与阳性对照组rBmKAGAP比较均下调,具有显著性差异。结论二硫键C16-C36和C22-C46在保持和调节BmK AGAP的镇痛生物活性方面具有重要作用。     

蝎镇痛抗菌活性肽BmK AS的融合表达及蛋白切割

目的构建镇痛抗菌活性肽BmK AS原核融合表达载体,实现可溶性表达,获得重组活性肽BmK AS。方法利用本实验室已构建成功的pET 28a-AS质粒,设计引物经过聚合酶链式反应,将目的基因克隆至pET 32a载体中,构建融合表达载体pET 32a-AS,优化诱导表达条件,实现BmK AS在大肠杆菌BL21(DE 3)中的融合可溶性表达,通过金属离子螯合亲和薄层色谱法对重组蛋白进行初步分离纯化,获得重组融合蛋白后采用凝血酶进行切割去除纯化标签,经SDS-PAGE检测切割效果。结果成功构建重组表达质粒,优化得到低温诱导促进蛋白可溶性表达的方法;采用金属离子螯合亲和薄层色谱法获得重组蛋白;电泳结果表明凝血酶可以切割融合蛋白。结论实现活性肽BmK AS在大肠杆菌中的融合可溶性表达,经凝血酶切割后获得重组镇痛抗菌活性肽BmK AS,为后续药理活性研究奠定基础。     

5种人细胞色素P450 2A13突变体的异源表达及其香豆素代谢活性

目的重组表达人细胞色素P450(CYP)2A13突变体CYP2A13*2,CYP2A13*5,CYP2A13*6,CYP2A13*8和CYP2A13*9,并研究CYP2A13突变体与野生型CYP2A13(CYP2A13*1)对香豆素的代谢活性上的差异。方法通过点突变法构建各CYP2A13突变体。用杆状病毒表达系统制备含各突变体c DNA的重组病毒,并将其与含人源还原型烟酰胺腺嘌呤二核苷磷酸P450氧化还原酶(POR,野生型)的重组杆状病毒共转染昆虫草地夜蛾细胞(sf9),共表达CYP2A13突变体和POR重组蛋白。将表达产物制备成微粒体与香豆素(0.25~25μmol·L-1)体外孵育30 min,高效液相色谱法测定各重组酶对香豆素的代谢活性。结果Western蛋白印迹结果表明,各重组酶在sf9细胞中得到了表达。体外代谢实验显示,CYP2A13野生型及其突变体蛋白代谢香豆素在Km值上无显著差异,而在Vmax(mol·min-1·mol-1CYP)上,CYP2A13*2(0.58±0.05,P<0.05)、CYP2A13*5(0.71±0.08,P<0.01)、CYP2A13*6(0.84±0.09,P<0.01)、CYP2A13*9(0.58±0.04,P<0.05)等突变体与CYP2A13*1(0.33±0.06)相比有显著性差异,使得这4个突变体的代谢效率增加了40%~108%。结论体外成功表达了具有活性的CYP2A13*2,CYP2A13*5,CYP2A13*6,CYP2A13*8和CYP2A13*9重组蛋白。CYP2A13*2,CYP2A13*5,CYP2A13*6和CYP2A13*9等突变体的香豆素代谢活性明显高于CYP2A13*1。     

重组人角质细胞生长因子-1突变体表达载体的构建

目的构建重组人角质细胞生长因子-1突变体的表达载体。方法采用PCR突变方法,将rhKGF cDNA第40位的Cys密码子突变为Ser密码子,所得的突变片断插入表达载体的表达框架中。结果 DNA测序分别证实合成的基因序列克隆入pET-22b中。结论构建重组人角质细胞生长因子-1突变体的表达载体,得到突变体蛋白40位丝氨酸突变截短型角质细胞生长因子[Ser40]rhKGFdest-23。     

重组CD_(13)单链抗体和蝎毒素多肽AGAP融合蛋白真核表达及对NB4细胞的靶向杀伤作用

目的:本研究应用基因工程技术方法,构建含重组编码CD13单链抗体和蝎毒素镇痛抗肿瘤缬精甘肽(analgesic antitumoral peptide,AGAP)融合蛋白基因的表达载体,并研究CD13-AGAP融合蛋白对CD13阳性白血病细胞NB4影响。方法:克隆东亚钳蝎活性肽AGAP的基因,插入真核表达载体pSecTag2/CD13/RFP,得到pSecTag2/CD13/AGAP重组真核表达载体。酶切及测序鉴定后,脂质体介导重组质粒转染293T细胞,通过RT-PCR和免疫印迹方法检测融合基因和蛋白的表达。纯化融合蛋白,作用NB4细胞,CCK8检测细胞活性,流式细胞仪检测细胞周期。结果:酶切及测序结果证实pSecTag2/CD13/AGAP重组真核表达载体构建成功,转染293T细胞后,RT-PCR和免疫印迹方法结果证实重组质粒得到有效表达,并纯化真核表达融合蛋白CD13-AGAP对血液肿瘤CD13阳性白血病细胞NB4有一定的生长抑制作用,并且使细胞周期G1期阻滞,S期减少。结论:成功构建了融合蛋白真核表达载体pSecTag2/CD13/AGAP,并在293T细胞中成功表达,进一步证实融合蛋白对CD13阳性白...     

人细胞色素P450 3A4突变体CYP3A4.3,CYP3A4.4,CYP3A4.5和CYP3A4.18重组酶的异源表达与活性

目的重组表达人细胞色素P450(CYP)3A4突变体CYP3A4.3,CYP3A4.4,CYP3A4.5和CYP3A4.18蛋白,为CYP3A4代谢活性的体外研究提供单一酶源。方法应用杆状病毒表达系统构建含有上述各CYP3A4突变体基因序列的重组病毒,将其连同含人源还原型烟酰胺腺嘌呤二核苷磷酸-P450氧化还原酶(POR)和细胞色素b5基因的重组病毒共同感染昆虫草地夜蛾细胞Sf9得到CYP3A4突变体与POR和细胞色素b5共表达的重组蛋白,分别以高效液相色谱法和荧光分析法测定各重组酶对睾酮和7-甲氧基-4-三氟甲基香豆素的代谢活性。结果在mRNA分子水平上验证了CYP3A4突变体CYP3A4*3,CYP3A4*4,CYP3A4*5和CYP3A4*18基因在Sf9细胞中的转录。感染了各重组病毒的Sf9细胞裂解液对睾酮和7-苄氧基-4-三氟甲基香豆素有明显代谢。结论应用杆状病毒-昆虫细胞表达系统在体外成功表达了具有催化活性的人CYP3A4突变体CYP3A4.3,CYP3A4.4,CYP3A4.5和CYP3A4.18蛋白,其中CYP3A4.5活性显著低于野生型蛋白,CYP3A4.18活性显著高于野生型蛋白,而CYP3A4.3和CYP3A4.4与野生型蛋白活性近似。     

乳铁素的融合表达及其体外抗菌活性鉴定

为降低乳铁素Lf-cinB表达时对宿主细胞的毒害,提高乳铁素的表达量及纯化效果,合成了牛乳铁蛋白肽基因,克隆至E.coli表达载体pTYB11中,构建了与蛋白质内含子(intein)的C端融合的表达载体pTYB11-cinB。重组质粒转化至E.coliBL21(DE3)中,经IPTG诱导表达,融合蛋白intein-cinB主要以可溶形式存在于胞内。利用载体中intein中的chitin结合域,将融合蛋白通过chitin亲和层析一步纯化,经DTT诱导in-tein的自我切割活性,实现Lf-cinB在亲和柱上的切割与分离,透析冻干后得到了纯度94%的重组Lf-cinB。活性检测结果显示,重组Lf-cinB对多种检测菌均有抗菌活性。研究认为,内含肽在抗菌肽的基因工程中具有重要的应用前景。     

人β-防御素DEFB113的重组表达及活性鉴定

DEFB113为人β-防御素家族新成员,其生物学功能尚不清楚。为了探索一种可以较低成本和较高产量表达活性DEFB113多肽的方法,将编码DEFB113成熟肽的序列克隆到载体pTWIN1上,并转化至E.coliBL21(DE3)中进行表达。结果表明融合蛋白主要以可溶形式存在;重组载体中融合标签的几丁质结合域(CBD)和内含肽(intein)分别使亲和层析纯化和融合标签自剪切一步完成。最终得到DEFB113多肽的产率为6～7 mg/LLB。经活性鉴定,该重组DEFB113多肽对于S.aureus,E.coli K12D31和C.albicans均表现出较强的抑制作用;另外DEFB113无明显的溶血活性,是一种较理想的多肽抗生素。该研究为进一步研究DEFB113的生理功能以及其它人β-防御素结构与功能奠定了基础。     

两种具有双功能活性蝎毒蛋白融合体的构建

目的首次报道利用东亚钳蝎镇痛抗肿瘤缬精甘肽-BmKAGAP产生两种不同的融合蛋白,目的是获得镇痛和抗肿瘤的双功能活性。方法融合蛋白是以嵌合毒素的形式进行构建,由三部分组成,包括促性腺激素释放激素(luteinizing hormone-releasing hormoneL,HRH),两种不同类型的柔性连接物,以及BmKAGAP。克隆编码两种融合蛋白的基因并在大肠杆菌中实现可溶性表达。通过金属离子螯合亲和层析和阳离子交换层析方法对融合蛋白分离纯化,采用小鼠醋酸扭体法和MTT法测定融合蛋白的镇痛活性与细胞抑制活性。结果融合蛋白在小鼠模型中体现出镇痛活性(rLHRH-Tag(His)AGAP>rTag(His)-LHRH-L8-AGAP>rBmKAGAP),同时对肝癌细胞株Hep3B具有细胞毒活性(rLHRH-Tag(His)-AGAP>rBmKAGAP>rTag(His)-LHRH-L8-AGAP)。结论得到优化的双功能融合蛋白候选者为嵌合毒素rLHRH-Tag(His)-AGAP。     

Huwentoxin-V, a novel insecticidal peptide toxin from the spider Selenocosmia huwena, and a natural mutant of the toxin: indicates the key amino acid residues related to the biological activity.

A neurotoxin peptide (named Huwentoxin-V) was purified from the venom of the Chinese bird spider Selenocosmia huwena by a combination of ion exchange chromatography and reverse phase HPLC. HWTX-V has 35 amino acid residues, and is in perfect agreement with the molecular mass 4111.4 Da identified by mass spectrometry. A natural mutant of the toxin (called mHuwentoxin-V) was also isolated from the venom. mHWTX-V was only truncated two amino acid residues from the C-terminus of HWTX-V, and its molecular weight is 3877.1 Da determined by mass spectrometry. The six cysteine residues in each sequence of the two peptides suggest three disulfide bridges, the present of which was demonstrated by mass spectrometry after dithiothreiotol reduce and S-carboxymethylation. The primary structure of the two toxins exhibits sequence identity with other spider toxins such as ProTx-I (64%), SGTx (57%), SNX-482 (55%), and Hanatoxin (54%). HWTX-V can reversibly paralyze locusts and cockroaches for several hours with a ED50 value as 16 +/- 5 microg/g to locusts, and a larger dose of the toxin can cause death. However, mHWTX-V shows no significant effect on locusts and cockroaches. The structure-activity relationship indicates that the residues Phe34 and Ser35 in the C-terminus of HWTX-V are the key residues of the biological activity.     

重组小鼠CK2α亚基在大肠杆菌中的表达、纯化及活性测定

目的　研究重组小鼠CK2α亚基在大肠杆菌中的表达 ,并进行纯化和活性的测定。方法　将已构建成功的小鼠蛋白激酶CK2α亚基cDNA的重组质粒 ,转化大肠杆菌BL2 1(DE3) ,IPTG诱导表达 ,产物依次进行DE 5 2、P11磷酸纤维素和肝素 Sepharose柱层析分离 ,SDS PAGE银染。结果　重组质粒转化表达菌经IPTG诱导后出现一分子量为 4 2ku蛋白过度表达 ,表达蛋白约占菌体总蛋白的 30 6 %。从2 87mg可溶性蛋白质中得到 4 7mg纯化蛋白。SDS PAGE银染显示纯化的蛋白为单一蛋白带。纯化的CK2α和 β亚基等摩尔分子混合可组成有完全活性的全酶。重组的CK2全酶的性质和功能与该酶的已知特性一致。结论　重组蛋白是小鼠蛋白激酶CK2α亚基     

Disparate ligand-mediated Ca(2+) responses by wild-type, mutant Ser(200)Ala and Ser(204)Ala alpha(2A)-adrenoceptor: G(alpha15) fusion proteins: evidence for multiple ligand-activation binding sites

Ligand : receptor interactions were analysed at wt, mutant Ser(200)Ala and Ser(204)Ala alpha(2A) ARs by measuring Ca(2+) responses in CHO-K1 cells either by co-expression with a G(alpha15) protein or at a receptor : G(alpha15) protein stoichiometry of 1.0 using fusion proteins. The magnitude of the UK 14304-mediated Ca(2+) response as elicited by a G(alpha15) protein was largest with both mutant Ser(200)Ala and Ser(204)Ala alpha(2A)ARs compared to the wt alpha(2A) AR in the co-expression and fusion protein experiments. The activation profiles of the wt and both mutant alpha(2A) ARs as analysed by a series of alpha(2) AR agonists differed. d-Medetomidine and clonidine appeared most efficacious at the Ser(204)Ala alpha(2A) AR, whereas oxymetazoline was also partially active at the Ser(200)Ala alpha(2A) AR. Talipexole was silent at both mutant alpha(2A) ARs. The intrinsic activity of (-)-adrenaline was either absent or partial at the Ser(204)Ala and Ser(200)Ala alpha(2A) AR, respectively. This latter observation is related to its lower binding affinity for both mutant alpha(2A) ARs. Ligands characterized as antagonists at wt and Ser(200)Ala alpha(2A) ARs demonstrated either no intrinsic activity (i.e., RX 811059) or positive efficacy with a different rank order of maximal response at the Ser(204)Ala alpha(2A) AR (atipamezole=SKF 86466=idazoxan>dexefaroxan) than Asp(79)Asn alpha(2A) AR (atipamezole>idazoxan approximately SKF 86466>dexefaroxan) and Thr(373)Lys alpha(2A) AR (SKF 86466>atipamezole approximately idazoxan>dexefaroxan). These effects were only observed in the co-expression experiments at concentrations in line with their binding affinities. In conclusion, these Ca(2+) data suggest that multiple activation binding sites exist for these ligands at the alpha(2A) AR, and that their activation may be affected in different ways by the mutations being investigated.     

Manipulation of cellular GSH biosynthetic capacity via TAT-mediated protein transduction of wild-type or a dominant-negative mutant of glutamate cysteine ligase alters cell sensitivity to oxidant-induced cytotoxicity

The glutathione (GSH) antioxidant defense system plays a central role in protecting mammalian cells against oxidative injury. Glutamate cysteine ligase (GCL) is the rate-limiting enzyme in GSH biosynthesis and is a heterodimeric holoenzyme composed of catalytic (GCLC) and modifier (GCLM) subunits. As a means of assessing the cytoprotective effects of enhanced GSH biosynthetic capacity, we have developed a protein transduction approach whereby recombinant GCL protein can be rapidly and directly transferred into cells when coupled to the HIV TAT protein transduction domain. Bacterial expression vectors encoding TAT fusion proteins of both GCL subunits were generated and recombinant fusion proteins were synthesized and purified to near homogeneity. The TAT-GCL fusion proteins were capable of heterodimerization and formation of functional GCL holoenzyme in vitro. Exposure of Hepa-1c1c7 cells to the TAT-GCL fusion proteins resulted in the time- and dose-dependent transduction of both GCL subunits and increased cellular GCL activity and GSH levels. A heterodimerization-competent, enzymatically deficient GCLC-TAT mutant was also generated in an attempt to create a dominant-negative suppressor of GCL. Transduction of cells with a catalytically inactive GCLC(E103A)-TAT mutant decreased cellular GCL activity in a dose-dependent manner. TAT-mediated manipulation of cellular GCL activity was also functionally relevant as transduction with wild-type GCLC(WT)-TAT or mutant GCLC(E103A)-TAT conferred protection or enhanced sensitivity to H₂O₂-induced cell death, respectively. These findings demonstrate that TAT-mediated transduction of wild-type or dominant-inhibitory mutants of the GCL subunits is a viable means of manipulating cellular GCL activity to assess the effects of altered GSH biosynthetic capacity.     

重组人和大鼠醇脱氢酶、醛-酮还原酶的克隆表达及应用

克隆、表达人和大鼠醇脱氢酶 (ADH)、醛-酮还原酶 (AKR) 基因全长cDNA, 研究扁桃酸 (MA) 代谢机制。设计引物, 利用RT-PCR克隆人和大鼠醇脱氢酶、醛-酮还原酶基因全长cDNA。测序正确的cDNA被克隆到表达载体pET-28a (+) 上并在大肠杆菌BL21 (DE3) 中稳定表达。利用亲和色谱纯化相应的酶, 通过检测其在340 nm吸收度值的变化进行酶活性测定。获得的醇脱氢酶与扁桃酸, 醛-酮还原酶与苯乙酮酸 (PGA) 共孵育, 采用HPLC分析其代谢和转化情况。通过测序, 目的蛋白的cDNA序列完全正确, 在宿主菌中获得良好的可溶性表达, 经Ni²⁺亲和柱纯化后目的蛋白达到了电泳纯, 具有较好的催化活性。人ADH2对扁桃酸的代谢具有立体选择性, 优先代谢S-MA, 对S-MA的代谢能力较强。大鼠ADH1对扁桃酸无代谢活性, 人和大鼠AKR对苯乙酮酸均无代谢。成功构建人和大鼠醇脱氢酶、醛-酮还原酶的表达质粒, 获得高活性的蛋白。这些重组酶模型可以用于由醇脱氢酶和醛-酮还原酶介导的药物代谢研究。     

sCR1在原核中表达、纯化、复性及活性鉴定

目的采用原核表达载体pET28a在E.coli BL21(DE3)中获得高表达、高活性的重组人sCR1融合蛋白。方法从人外周血中提取总RNA,应用RT-PCR获得人sCR1全长cDNA,将其克隆入原核表达载体pET28a中,构建含人sCR1的重组质粒(pET28a-sCR1),经测序鉴定正确,转化入E.coli BL21(DE3)中,经IPTG诱导,表达产物经SDS-PAGE分析和Western blot鉴定,通过Ni2+-NTA agarose亲和层析纯化后进行复性及生物学活性鉴定。结果获得原核表达载体pET28a-sCR1,经PCR鉴定及测序鉴定,得到重组E.coli BL21(DE3)克隆菌株,经IPTG诱导含有pET28a-sCR1的E.coli BL21(DE3)克隆菌,表达出重组人sCR1融合蛋白。此蛋白在SDS-PAGE上表现为Mr大于29000的蛋白区带,在Western blot分析中可被sCR1的CD35单克隆单抗体(mAb)识别。经Ni2+-NTA agarose亲和层析纯化、复性后得到高纯度的sCR1融合蛋白表达及较高的生物学活性。结论人sCR1融合蛋白在E.coli BL21(DE3)表达系统中的高水平表达,并且有与人体天然蛋白相同的抗原性及其生物学活性。     

Modification of serine 360 by a reactive intermediate of 17-alpha-ethynylestradiol results in mechanism-based inactivation of cytochrome P450s 2B1 and 2B6

17-alpha-Ethynylestradiol (17EE) is a mechanism-based inactivator of P450 2B1 and P450 2B6 in the reconstituted monooxygenase system. The loss in enzymatic activity was due to the binding of a reactive intermediate of 17EE to the apoprotein. P450 2B1 and P450 2B6 were inactivated by 17EE and digested with trypsin. The peptides obtained following digestion with trypsin of 17EE-inactivated P450 2B1 and P450 2B6 were separated by liquid chromatography and analyzed by ESI-MS. Adducted peptides exhibiting an increase in mass consistent with the addition of the mass of the reactive intermediate of 17EE were identified for each enzyme. Analysis of these modified peptides by ESI-MS/MS and precursor ion scanning facilitated the identification of the Ser360 in both enzymes as a site that had been adducted by a reactive intermediate of 17EE. A P450 2B1 mutant where Ser360 was replaced by alanine was constructed, expressed, and purified. Activity and inactivation studies indicated that mutation of the Ser360 residue to alanine did not prevent inactivation of the mutant enzyme by 17EE. These observations suggest that Ser360 is not critical for the catalytic function of these P450s. Spectral binding studies of the 17EE-inactivated P450 2B1 and P450 2B6 indicated that modification of the enzymes by the reactive intermediate of 17EE resulted in an enzyme that was no longer capable of binding substrates. These results suggest that the inactivation by 17EE may be due to modification of an amino acid residue in the substrate access channel near the point of entry into the active site.