大肠杆菌AroG蛋白F209S突变体对苯丙氨酸反馈抑制作？…

在大肠杆菌中,８０％的３－脱氧－Ｄ－阿拉伯－庚酮－７－磷酸（３－ｄｅｏｘｙ－Ｄ－ａｒａｂｉｎｏ－ｈｅｐｔｕｌｏｓｏａｔｅ ７－ｐｈｏｓｐｈａｔｅ,ＤＡＨＰ）合酶由ａｒｏ基因编码。分别以大肠杆菌Ｋ１２及其抗苯丙氨酸类似物的突变体总ＤＮＡ为模板,以ＰＣＲ方法扩增得到ａｒｏＧ基因及其突变。基因测序结果表明抗苯丙氨酸灯似物的突变体,其ａｒｏＧ基因核苷酸６２５位发生了Ｔ→Ｃ的点突变,从而使ＡｒｏＧ蛋白的２０     

大肠杆菌CM/PDT抗反馈抑制突变体的构建及其性质

为了获得具有高催化活性且抗反馈抑制的大肠杆菌分支酸变位酶 预苯酸脱水酶 (chorismatemutase prephenatedehydrataseCM PDT) [EC5 .4 .99.5 EC4 .2 .1.5 1],通过相关菌种CM PDT氨基酸序列同源比较 ,寻找高度保守位点 .用定点突变及PCR法构建突变酶M1(缺失 30 4T、30 5G、Q30 6K)、M2 (缺失W 338)、M3(缺失 30 1～ 386位氨基酸 )、M32 9(E32 9A)和M374 (C374A) ,野生型及各突变型基因与pET2 8a(+ )载体连接后 ,表达融合蛋白 .在非变性条件下 ,由TALON金属螯合亲和层析柱纯化野生型和突变体的酶蛋白 .酶活性测定表明 ,突变体M3的PDT活性下降为野生型活性的 2 9% ,但保持了CM活性 .突变体M374保持了CM ,PDT两种酶的活性 ,突变体M1、M2、M32 9的CM ,PDT活性有一定程度的提高 .酶抗反馈抑制作用检测表明 ,突变体M3、M374解除了苯丙氨酸的反馈抑制作用 ,M1、M2、M32 9部分解除了苯丙氨酸的反馈抑制作用 .与含野生型pheA基因的E .coliBL2 1菌株相比 ,含突变基因的E .coliBL2 1菌株对 10mmol L的苯丙氨酸代谢类似物具有强的抗反馈抑制作用 ,其中M1,M2 ,M3对 2 0mmol L的类似物具有抗反馈抑制作用     

苯丙氨酸合成的关键酶基因aroG与pheA串联表达

aroG和pheA是与苯丙氨酸合成有关的两个重要基因。在大肠杆菌(Escherichia coli)中,aroG基因编码脱氧阿拉伯糖型庚酮糖磷酸合酶(DS),该酶催化由糖代谢中心途径分流出来的磷酸烯醇丙酮酸(PEP)和赤鲜糖4磷酸(E4P)缩合形成脱氧阿拉伯糖型庚酮糖磷酸(DAHP)的反应;pheA基因编码一个双功能酶蛋白,它同时催化两步关键反应,即具有分枝酸变位酶(CM)和预苯酸脱水(PD)的两种功能。采用PCR技术分别从两个不同品系的大肠杆菌染色体DNA中扩增到aroG和pheA。当这两个基因串联在一个质粒上导入大肠杆菌P2392中进行表达时,它们编码的酶DS、CM和PD活性分别提高43、44和22倍;导入短杆菌(Brevibacterium)2731中表达时,相应的酶活性分别提高123、23和56倍。两基因的串联表达能大幅度地提高工程菌株的苯丙氨酸发酵产量。     

抗酶1基因转染对HeLa细胞增殖及细胞周期的抑制作用

研究抗酶(antizyme)1对人宫颈癌HeLa细胞增殖与细胞周期的影响,并分析抗酶1对细胞周期蛋白D1(cyclin D1)的表达影响.采用定点突变技术,将抗酶1的frameshift位点缺失,随后将突变基因重组至真核表达载体pEGFP-N1中,鉴定后转染HeLa细胞.通过MTT法检测细胞增殖变化,流式细胞术分析抗酶1对细胞周期的影响.RT-PCR和Western印迹检测抗酶1转染对细胞周期蛋白 D1基因表达的影响.酶切结果显示,抗酶1突变基因成功克隆至pEGFP-N1中.成功转染HeLa细胞后,检测结果显示,抗酶1能够减慢HeLa细胞增殖速度,并使细胞停滞于G₀/G₁期,细胞周期蛋白D1基因的表达同时受到抑制.实验说明,抗酶1基因能够抑制HeLa细胞增殖,通过降低细胞周期蛋白D1的表达阻滞细胞周期.     

基于易错PCR定向进化扩展青霉 Penicillium expansum FS1884碱性脂肪酶

为改善扩展青霉FS1884碱性脂肪酶的活性及酶学性质,利用连续两轮易错PCR对扩展青霉FS1884脂肪酶基因PEL进行随机突变,在大肠杆菌JM109中构建突变文库。含突变脂肪酶基因的重组质粒电击转化巴斯德毕赤酵母GS115,经过YPOM板初筛和橄榄油检验板复筛,获得一株酶活性提高的脂肪酶突变体:PEL-ep25-GS。与野生型脂肪酶PEL-GS相比,在最适温度40℃、pH9.4时突变体的酶活力是野生型酶的1.3倍。测序结果表明:该突变体第253位氨基酸发生了突变,由赖氨酸变成蛋氨酸。     

次黄嘌呤-鸟嘌呤磷酸核糖转移酶突变体的基因构建、表达和性质

通过对我国嗜热菌Thermoanaerobactertengcongensis中次黄嘌呤 鸟嘌呤磷酸核糖转移酶 (HGPRT)三维结构进行同源模建 ,设计出HGPRT的突变体K1 33A、K1 33S和K1 33T。用抗性筛选法 ,对HGPRT的基因进行了定点突变 ,并实现了在大肠杆菌中的高效表达。野生型HGPRT及其突变体K1 33A、K1 33S和K1 33T的催化动力学研究表明 ,HG PRT突变体改变并扩大了底物专一性 ,具有催化嘌呤类似物的活性。     

枯草芽孢杆菌耐盐突变株proA基因克隆及proBA基因渗透压调节功能研究

利用TaKaRaLAPCRTM试剂盒扩增枯草芽孢杆菌 931 5 1耐盐突变株proA基因的未知下游序列。根据测序结果 ,设计引物 ,克隆出发菌株和突变株全长proBA基因。将出发菌株和突变株的proBA基因分别转化大肠杆菌JM83(proBA- ) ,均能够与其功能互补。SDS PAGE分析其表达产物 ,有两条分子量分别约为 4 0kD和 4 5kD的新蛋白带出现。测定 4种转化子 (分别含有出发菌株和突变株proB基因的大肠杆菌 1 1 2 5 2转化子及proBA基因的大肠杆菌JM83转化子 )的耐盐能力。发现含有突变株proB或proBA基因转化子的耐盐能力 ,均比相应的含有出发菌株proB或proBA基因的转化子高。另外含有出发菌株和突变株的proBA基因转化子的耐盐能力 ,也均比相应的仅含proB基因的转化子高 ,表明枯草芽孢杆菌的ProA比大肠杆菌的ProA更为有效。测定所有JM83转化子胞内自由脯氨酸 ,发现其含量随盐浓度的上升而提高 ,其中含突变菌株proBA基因的转化子提高更为显著     

大肠杆菌tyrR基因剔除及其对苯丙氨酸生物合成的影响

TyrR是大肠杆菌芳香族氨基酸生物合成和运输途径中的一种全局性调控蛋白质。采用双交换同源重组的方法定位突变大肠杆菌染色体tyrR基因 ,在该基因中插入带有卡那霉素抗性基因的DNA片段 ,使之失活 ,实现基因剔除。经PCR、DNA测序、lacZ报告基因等多种方法证实了基因剔除的可靠性。tyrR基因剔除后 ,大肠杆菌芳香族氨基酸生物合成中受TyrR蛋白调控的关键酶的酶活力有所提高 :3 脱氧 2 阿拉伯庚酮糖 7 磷酸合成酶(DAHPS ,由aroG编码 )酶活力提高了 1.0 8倍 ,转氨酶 (AT ,由tyrB编码 )酶活力提高了 2 .70倍 ;突变菌株发酵生产苯丙氨酸的能力提高了 1.5 9倍 ;同时 ,与芳香族氨基酸运输相关的通透酶基因aroP(P)的阻遏被解除 ,细胞运输芳香族氨基酸的能力提高了 70 .2 %。     

大肠杆菌tyrR基因对aroP的表达调控

大肠杆菌的tyrR基因编码芳香氨基酸生物合成和运输途径中的一种全局性调控蛋白质,该蛋白质控制着包括自身编码基因tyrR在内的涉及苯丙氨酸、酪氨酸、色氨酸合成与运输的8个转录单位的转录。大肠杆菌aroP基因编码一种跨质膜主动运输芳香氨基酸的透性酶,其转录也受TyrR蛋白抑制。利用PCR反应从E.coli K12基因组中分别克隆了aroP(p)基因(携带自身的启动子)、aroP基因(不携带自身的启动子)和tyrR基因,并将它们导入苯丙氨酸生产菌E.coli WT5中。通过大细胞法检测到这3个基因的表达,并分别测定了相应的酶活力。结果:发现导入aroP(p)和aroP基因的大肠杆菌吸收苯丙氨酸的能力分别提高到原来的1．40和1．46倍,这表明利用pλPR质粒能够表达aroP基因,该质粒中的λ右向启动子(R)和aroP自身启动子(p)的表达效率几乎同样;导入tyrR基因的E．coli WT5 ATP酶活力提高到原来的1．69倍。将两种基因串联克隆在同一质粒中共表达时,携带aroP-tyr串联的大肠杆菌株运输苯丙氨酸的能力明显高于携带aroP(p)-tyrR串联的大肠杆菌株。以E．coli WT5为对照,其AroP的活性定为1,前者的Atop相对酶活力为1．31,后者为0．95,这一结果显示TyrR蛋白可能是通过与aroP基因自身启动子的结合作用来负调控aroP基因的表达。     

FABP5基因重组突变体蛋白抗前列腺癌细胞活性分析

为构建脂肪酸结合蛋白5 (FABP5)突变体的原核表达体系,评价突变体蛋白质体外抗前列腺癌细胞的活性.利用定点突变技术,突变FABP5蛋白脂肪酸结合的3个关键位点,并构建原核表达体系,对重组蛋白质进行原核表达、分离纯化.通过细胞毒性、细胞划痕和细胞侵袭试验,评价重组FABP5突变体蛋白质对前列腺癌细胞22RV1和PC3增殖、迁移和侵袭的影响.结果 显示定点突变后的DNA与表达载体pQE32连接并转入大肠杆菌(Escherichia coli) BL21(DE3),经序列测定正确,构建了重组表达工程菌,并诱导表达的重组蛋白经亲和层析纯化获得纯度较高的重组蛋白;三突变体对细胞的增殖、迁移和侵袭抑制作用比3个单突变体和3个双突变体抑制效果明显;单突变体和双突变体组内对细胞的增殖、迁移和侵袭抑制作用差异较小;而野生型重组蛋白质对两株细胞的增殖、迁移和侵袭具有促进作用.本研究从所有突变体中筛选出FABP5的三突变体重组蛋白质对前列腺癌细胞抑制作用较好,为后续开发去势抵抗性前列腺癌(CRPC)蛋白质药物提供参考.     

六种藓类植物茎的比较解剖学研究

通过对6种藓类植物,即褶叶青藓(Brachythecium salebrosum(Web.et Mohr.)B.S.G.)、湿地匐灯藓(Plagiomnium acutum(Lindb.)Kop.)、侧枝匐灯藓(Plagiomnium maximoviczii(Lindb.)Kop.)、大凤尾藓(Fissidensnobilis Griff.)、大羽藓(Thuidium cymbifolium(Doz.et Molk.)B.S.G.)和大灰藓(Hypnum plumaeforme Wils.)嫩茎和老茎的石蜡切片和显微观察发现,同一藓类植株的嫩茎和老茎,茎结构稳定,不同种藓类植物茎横切面具有不同特征.植物体茎横切面形状、表层细胞的层数、细胞大小和细胞壁厚薄、皮层细胞大小和形状、中轴的有无以及比例等特征可以作为藓类植物的分科分类依据之一.     

Photoregulation of seed germination of wild-type and of an aurea-mutant of tomato

Seed germination of an aurea mutant of tomato ( Lycopersicon esculentum Mill.) is promoted by continuous irradiation with red, far-red or long-wavelength far-red (758 nm) light as well as by cyclic irradiations (5 min red or 5 min far-red/25 min darkness). Far-red light applied immediately after each red does not change the germination behaviour. Seed germination of the isogenic wild-type, cv. UC-105, is promoted by continuous and cyclic red light while it is inhibited by continuous and cyclic far-red light and by continious 758 nm irradiation. Far-red irradiation reverses almost completely the promoting effect of red light. The promoting effect (in the aurea mutant) and the inhibitory effect (in the wild-type) of continuous far-red light do not show photon fluence rate dependency above 20 nmol m⁻² s⁻¹. It is concluded that phytochrome controls tomato seed germination throgh low energy responses in both the wild type and the au mutant. The promoting effect of continuous and cyclic far-red light in the au mutant can be attributed to a greater sensitivity to P_fr.     

Cause of Senescence of Nine Sorts of Flowers

The levels of endogenous phytohormones and respiratory rate in nine sorts of flowers such as Cymbidium faberi Rolfe, Nopalxochia ackermannii Kunth and others were investigated both at full bloom and senescence and meanwhile the effect of exogenous phytohormones on prolonging the blossoms and promoting ethylene production were tested. There is a high content of endogenous ethylene in all the long-lived flowere, about 3–16 folds higer than the short-lived ones. There is a high level of ABA at full blooming flowers of short-lived flowers, in which there is no or only some cytokinins in it, but the ratio of CTK (6BA+zeatin)/ABA is smaller(l.7). The endogenous ABA reached a much higher level at senescence in all nine sorts of flowers, so it is reasonable to consider that it is ABA which plays an important role of regulation in controlling flower's senescence. There is a much higher level of GA3 and zeatin in the long-lived flowers which is not demonstrated in the shortlived ones. The respiratory rate is one of the factors controtling the longevity of flowers, but it does not play a decided role. Application of 6BA and zeatin prolongs distinctly orchid’s longevity, however exogenous IAA through the promotive action on ethylene production, evidently extends the longevity of the flowers of the Nopalxochia ackermannii Kunth.     

真菌类遗传学分析的知识结构教学

本文以认知结构理论为指导,讨论了真菌类遗传分析与高等动植物遗传分析的内在联系,认为利用这种内在联系进行教学可收到好的效果并说明了作者的具体教学过程。 Abstract:In the paper, the relationship between genetic analysis of Fungi and genetic analysis of high animal and plant was discussed.A good results were obtained when we adopted this method in the teaching.     

龙胆科药用植物化学成分的研究现状

龙胆科植物在我国的分布范围很广,且多数为药用植物,其多数种属的药用植物,至今其化学成分尚未被系统研究。综述了目前龙胆科药用植物的化学成分的研究现状及一般提取方法,对近年来发现的环烯醚萜及裂环烯醚萜类化合物进行了总结,为本科药用植物的更深入研究提供了参考。     

Interconnection of parameters of regulation system of lipid peroxidation and of morphophysiological parameters of mouse liver

A complex analysis of seasonal fluctuations of the mean group parameters of the system of regulation of lipid peroxidation has been performed in liver of Balb/c mice. Association of lipid characteristics and morphophysiological parameters is studied in the Balb/c mouse liver. An inter-connection is revealed between the liver index and the amount of lysoforms of phospholipids, the scale and character of the interconnection differing essentially depending on proportion of phos-phatidylcholine in mouse liver phospholipids.     

The effects of glutamine of the maintenance of embryogenic cultures of Cryptomeria japonica

Summary Embryogenic tissues of sugi (Cryptomeria japonica) were induced on a modified Campbell and Durzan (CD) medium containing 1 μM 2,4-dichlorophenoxyacetic acid (2,4-D) and 600 mg l⁻¹ glutamine, and subcultured in the medium of the same composition for over 1 yr. This resulted in a mixed culture of embryogenic and non-embryogenic cells. When embryogenic cells were isolated and cultured independently, their capacity to form embryogenic aggregates was lost. Thus, the non-embryogenic cells present within a mixed culture system were essential to the formation of embryogenic aggregates. When embryogenic tissues were isolated and cultured independently on a high glutamine-containing (2400 mg l⁻¹) medium, dry weights and endogenous levels of glutamine increased, and the tissue could generate a large number of embryogenic aggregates. Amino acid analysis of embryogenic and non-embryogenic cells from the maintenance culture indicated a higher level of glutamine was present in the latter. The high endogenous level of glutamine in the non-embryogenic portion of mixed cell masses may be the supplier of glutamine for maintaining the embryogenic property of the tissues.     

Specificity of action of piperidylcholine derivatives as substrates of cholinesterases of various origin

The review deals with study of enzymologic properties of a novel highly specific acetylcholinesterase substrate, N-(β-acetoxyethyl) piperidinium iodomethylate (“piperidylcholine”), and its 30 derivatives that were tested as effectors of cholinesterases of mammals and various species of Pacific squids. It was proven for the first time that responsible for specificity of action was structure of cyclic ammonium grouping of the alcohol part of molecule of the ester substrate. Analysis of specificity is performed based on enzymatic hydrolysis parameters—activity of catalytic center of cholinesterases and bimolecular constant of the reaction rate that are determined at optimal and low substrate concentrations. Among the specially synthesized group of thioester compounds there is revealed one more highly specific acetylcholinesterase substrate—N-(β-acetoxyethyl) piperidinium.