对虾Ran基因的克隆表达与蛋白质GTP结合活性分析

在对虾抑制性差减杂交(suppression subtractive hybridization,SSH)研究过程中,首次发现一段经同源比较为Ran基因的部分序列,在抗病对虾中上调表达.为了进一步探索对虾Ran基因的功能,通过RACE-PCR的方法克隆得到了对虾Ran基因全长共1441个碱基,其中开放阅读框为645个碱基,共编码215个氨基酸,这是首次在海洋无脊椎动物体内克隆到该基因.本研究还将该基因克隆到原核表达载体PGEX-4T-2中并转化大肠杆菌BL21,37℃下诱导6h,超声裂解表达菌株,结果表明GST-Ran融合蛋白在大肠杆菌中为可溶性表达,蛋白大小约为50ku,经纯化得到了纯度大于90%的GST-Ran融合蛋白.随后的GTP结合试验验证了Ran蛋白具有GTP结合活性.     

Rab39A多克隆抗体的制备与鉴定

制备抗人Rab39A多克隆抗体并进行纯化检测,以用于Rab39A功能的研究.选取免疫原性强且特异性高的羧基端42个氨基酸(176～217aa)作为目的片段.PCR法扩增并构建重组表达质粒pGEX-4T-1-Rab39C42.异丙基-β-D-硫代半乳糖苷(IPTG)诱导表达并纯化GST-Rab39C42融合蛋白,免疫新西兰兔,制备多克隆抗体.然后以亲和层析法纯化抗体,利用Western blot和免疫荧光检测抗体的特异性.结果表明,构建的原核表达载体经IPTG诱导后高效表达GST-Rab39C42蛋白,纯化后抗体质量浓度为1μg/μL;Western blot实验显示,抗体可以识别外源Rab39A蛋白和多个细胞系的内源Rab39A蛋白;抗体中和实验和RNA干扰实验证明了该抗体具有特异性.本研究成功构建了pGEX-4T-1-Rab39C42原核表达载体,并制备了特异性的抗人Rab39A兔多克隆抗体,为进一步研究Rab39A的功能提供了有力的支持.     

日本囊对虾Ran基因的克隆表达与蛋白质GTP结合活性分析

在日本囊对虾抑制性差减杂交(suppression subtractive hybrid ization,SSH)研究过程中,首次发现一段经同源比较为Ran基因的部分序列,在抗病日本囊对虾中上调表达.为了进一步探索日本囊对虾Ran基因的功能,通过RACE-PCR的方法克隆得到了日本囊对虾Ran基因全长共1 441个碱基,其中开放阅读框为645个碱基,共编码215个氨基酸,这是首次在海洋无脊椎动物体内克隆到该基因.还将该基因克隆到原核表达载体PGEX-4T-2中并转化大肠杆菌BL21,37℃下诱导6 h,超声裂解表达菌株,结果表明GST-Ran融合蛋白在大肠杆菌中为可溶性表达,蛋白大小约为50 ku,经纯化得到了纯度大于90%的GST-Ran融合蛋白.随后的GTP结合试验验证了Ran蛋白具有GTP结合活性.     

小麦(Triticum asetivum L.)杂交种下调表达的GTP结合蛋白基因TaRab的克隆与鉴定

杂种优势的形成与杂种一代中亲本基因的表达方式改变有关.为深入研究小麦杂种优势形成的分子机理,利用通过抑制性差减杂交(SSH)方法获得的小麦Rab类GTP结合蛋白基因片段为探针,筛选普通小麦品系3338三叶期叶片cDNA文库,获得了一个小麦Rab家族基因TaRab.同源性比较和序列分析显示,该基因与拟南芥Rab类GTP结合蛋白基因具有90%氨基酸序列相似性.结构分析表明,它具有GTP结合蛋白4个典型结构以及Rab家族成员特有的YYRGA结构域.半定量RT-PCR表达检测结果显示,TaRab基因在叶片的表达水平要高于其他组织器官.研究还发现,该基因在三叶期、分蘖盛期的根系和叶片中为杂种下调表达.采用电子定位方法,将TaRab基因初步定位在7B染色体的着丝粒区域和C-7DS5-0.36两个区域.在此基础上,对Rab蛋白基因差异表达与杂种优势表现的关系进行了讨论.     

对虾白斑综合症病毒P9蛋白转录水平的微阵列分析及其免疫荧光标记

从构建的对虾白斑综合症病毒cDNA文库中,我们筛选到一个拷贝数最高,编码82个氨基酸的基因(命名为p9,wsv230).该基因被克隆到pGEX-2T载体中进行GST融合蛋白的原核表达,纯化的融合蛋白GST-P9用于制备特异的多克隆抗体.利用微阵列技术和免疫荧光标记技术,对该蛋白的转录水平及其在感染细胞内的分布进行了初步研究,表明该基因为高丰度表达,推测是对虾白斑综合症病毒的一个重要基因.     

丙型肝炎病毒NS5A基因的克隆以及在原核和昆虫细胞中表达的研究

克隆了丙型肝炎病毒的NS5A基因，并在细菌和昆虫两种不同的系统中成功地进行了该基因的表达。利用PCR方法获得了NS5A完整的编码区并克隆到原核表达载体pGEX—KG上，在大肠杆菌中诱导表达了78kDa的NS5A与GST的融合蛋白。同时发现，融合蛋白被部分切割为50kDa的NS5A和28kDa的GST。在原核细胞中表达的78kDa和50kDa两种蛋白均具有较高的免疫原性，通过免疫家兔获得了高特异性的兔抗血清。另外，利用两种昆虫表达系统，即AcMN—PV和HaSNPV的Bac-to-Bac系统对NS5A进行了表达，表达产物为58kDa。     

盘基网柄菌allC的克隆、表达和多克隆抗体的制备

运用RT-PCR技术从盘基网柄菌(Dictyostelium discoideum)总mRNA中克隆到了尿囊酸酶基因(allC),该基因编码区开放读框长1 100bp,编码的蛋白约42kD.由于是在野生型和突变型细胞中差异表达的片段,表明该基因在盘基网柄菌多细胞发育中起到重要作用,因此将allC克隆入融合表达载体pET-32a(+),在大肠杆菌E.coliBL21(DE3)中进行诱导表达带有6个组氨酸标签的尿囊酸酶(ALC)融合蛋白,经镍柱亲和层析,获得了电泳纯蛋白.用纯化的融合蛋白免疫新西兰大白兔,制备多克隆抗体.ELISA测得制备的抗ALC蛋白的多克隆抗体的效价可达1∶64 000,Western Blotting检测证明该抗体有较强的针对ALC蛋白的专一性.这些数据表明重组质粒表达的ALC融合蛋白具有良好的抗原性,制备ALC的多克隆抗体有良好特异性和效价,能够满足针对ALC免疫印迹和细胞内定位检测等实验要求,为深入研究ALC蛋白在盘基网柄菌多细胞发育的功能作用提供了有力工具.     

菠菜43 kD叶绿素a结合蛋白编码基因克隆及原核表达条件优化

将菠菜43 kD叶绿素结合蛋白编码基因亚克隆至原核表达载体pET-28a上,构建重组表达质粒pET-28a-psbC转化感受态E.coli BL21(DE3),经IPTG诱导实现了外源基因的可溶性表达.探讨了含组氨酸标签融合蛋白的最佳表达条件(包括表达单克隆、时间、温度对表达的影响).利用Ni2+-Sepharose 4 Fast Flow亲合层析纯化出His-apo CP43蛋白.体外重组实验证实 His-apo CP43能特异结合叶绿素a,经过温和电泳分离纯化所得体外重组色素蛋白复合物具有与提取自类囊体膜的天然CP43相似(但不完全相同)的荧光特性.     

GST-SDF-1α融合蛋白的原核表达及纯化

构建融合重组表达载体并对其进行诱导表达蛋白以获得大量重组融合蛋白。通过PCR方法扩增出小鼠SDF-1α基因,克隆入pMD18T载体中,进行测序分析。将该基因亚克隆入原核表达载体pGEX-4T11中GST的下游构建重组质粒pGEX-4T1-SDF-1α,转化受态细胞BL21中,经IPTG诱导表达重组融合蛋白,对表达产物进行SDS-PAGE电泳检测分析。在约Mr36×103处出现一新生的蛋白条带。经灰度扫描检测,表达量约占菌体总蛋白的30%,纯化后得到了目的蛋白。成功克隆了小鼠的SDF-1α基因,并纯化融合基因GST-SDF-1α的原核表达产物。     

大肠杆菌中融合表达汉滩病毒S,M基因片段的研究

为在大肠杆菌中融合表达汉滩病毒囊膜糖蛋白G1与NP含主要抗原位点的片段 .将汉滩病毒 76 118株S基因编码区 5′端约 0 .7kb的片段与M基因编码G1的片段连接 ,克隆入 pGEX 4T2 ,构建嵌合基因原核表达载体 pGEX 4T2 S 0 .7G1,在大肠杆菌XL1 Blue中诱导GST S0 .7G1融合蛋白的表达 .表达产物用ELISA和Westernblot进行鉴定 .限制性内切酶酶切鉴定证明 ,成功构建了嵌合原核表达载体 pGEX 4T2 S0 .7G1.经IPTG诱导后 ,ELISA活性测定结果表明 ,该融合蛋白可与抗汉坦病毒NPmAb特异性结合 .Westernblot结果显示 ,诱导出相对分子质量 (Mr)大于 1× 10 5的S0 .7G1与GST的融合蛋白 ,并有一系列大小不等的可与抗汉坦病毒NPmAb特异性结合的蛋白带 .获得具有特异性结合活性的融合蛋白GST S0 .7G1,为汉滩病毒基因工程疫苗的研制奠定了基础     

Rab5 is necessary for the biogenesis of the endolysosomal system in vivo

An outstanding question is how cells control the number and size of membrane organelles. The small GTPase Rab5 has been proposed to be a master regulator of endosome biogenesis. Here, to test this hypothesis, we developed a mathematical model of endosome dependency on Rab5 and validated it by titrating down all three Rab5 isoforms in adult mouse liver using state-of-the-art RNA interference technology. Unexpectedly, the endocytic system was resilient to depletion of Rab5 and collapsed only when Rab5 decreased to a critical level. Loss of Rab5 below this threshold caused a marked reduction in the number of early endosomes, late endosomes and lysosomes, associated with a block of low-density lipoprotein endocytosis. Loss of endosomes caused failure to deliver apical proteins to the bile canaliculi, suggesting a requirement for polarized cargo sorting. Our results demonstrate for the first time, to our knowledge, the role of Rab5 as an endosome organizer in vivo and reveal the resilience mechanisms of the endocytic system.     

Exocytotic fusion is activated by Rab3a peptides.

Studies of intracellular traffic in yeast and mammalian systems have implicated members of the Rab family of small GTP-binding proteins as regulators of membrane fusion. We have used the patch clamp technique to measure exocytotic fusion events directly and investigate the role of GTP-binding proteins in regulating exocytosis in mast cells. Intracellular perfusion of mast cells with GTP-gamma S is sufficient to trigger complete exocytotic degranulation in the absence of other intracellular messengers. Here we show that GTP is a potent inhibitor of GTP-gamma S-induced degranulation, indicating that sustained activation of a GTP-binding protein is sufficient for membrane fusion. We have found that synthetic oligopeptides, corresponding to part of the effector domain of Rab3a, stimulate complete exocytotic degranulation, similar to that induced by GTP-gamma S. The response is selective for Rab3a sequence and is strictly dependent on Mg2+ and ATP. This suggests that sustained activation of a Rab3 protein causes exocytotic fusion. The peptide response can be accelerated by GDP-beta S, suggesting that Rab3a peptides compete with endogenous Rab3 proteins for a binding site on a target effector protein, which causes fusion on activation.     

The Rab5 effector EEA1 is a core component of endosome docking

Intracellular membrane docking and fusion requires the interplay between soluble factors and SNAREs. The SNARE hypothesis postulates that pairing between a vesicular v-SNARE and a target membrane z-SNARE is the primary molecular interaction underlying the specificity of vesicle targeting as well as lipid bilayer fusion. This proposal is supported by recent studies using a minimal artificial system. However, several observations demonstrate that SNAREs function at multiple transport steps and can pair promiscuously, questioning the role of SNAREs in conveying vesicle targeting. Moreover, other proteins have been shown to be important in membrane docking or tethering. Therefore, if the minimal machinery is defined as the set of proteins sufficient to reproduce in vitro the fidelity of vesicle targeting, docking and fusion as in vivo, then SNAREs are not sufficient to specify vesicle targeting. Endosome fusion also requires cytosolic factors and is regulated by the small GTPase Rab5. Here we show that Rab5-interacting soluble proteins can completely substitute for cytosol in an in vivo endosome-fusion assay, and that the Rab5 effector EEA1 is the only factor necessary to confer minimal fusion activity. Rab5 and other associated proteins seem to act upstream of EEA1, implying that Rab5 effectors comprise both regulatory molecules and mechanical components of the membrane transport machinery. We further show that EEA1 mediates endosome docking and, together with SNAREs, leads to membrane fusion.     

恶性疟原虫复合多表位基因的原核表达和多克隆抗体制备

原核表达恶性疟原虫多期多表位基因并制备其多克隆抗体。在前期构建恶性疟原虫复合多期多表位重组真核表达载体的基础上,将测序正确的AMAMEG基因克隆入原核表达载体pGEX4T—1并诱导表达。采用包涵体洗涤的方式纯化目的蛋白,以AMA—1抗体对纯化蛋白进行Western—blot分析。将纯化的融合蛋白免疫小鼠制备多克隆抗体。通过PCR成功获得长度为1 000 bp的恶性疟原虫AMA—1胞外域基因片段,获得了与多表位基因连接后的AMAMEG基因。通过诱导表达,显示在相对分子量约95 000处有预计大小的特异性条带,表明成功表达出融合蛋白。经此纯化的融合蛋白免疫的小鼠能产生特异性抗体,其滴度达到1∶105。纯化的融合蛋白和多克隆抗体为研究新型疟疾疫苗奠定一定的理论和实践基础。     

GST融合蛋白包涵体纯化方法的探索

克隆结核分枝杆菌培养滤液蛋白CFP10基因,并在大肠杆菌中进行表达和纯化。用PCR方法从结核分枝杆菌H37Rv基因组扩增出CFP10基因片段,克隆至pMD18-T载体中,序列测定正确后,将其亚克隆到表达载体pGEX-4T-1并在大肠杆菌BL21中表达,表达蛋白经SDS-PAG及Western-blot分析后,亲和层析法纯化蛋白。成功克隆了CFP10基因,并对其在E.coli中进行了表达,SDS-PAGE及Western blot分析表明表达产物正确。通过GST纯化系统获得36kD纯化蛋白,与文献报道相符,该蛋白可与CFP10 mAb特异结合,并且同时与活动期结核病人血清发生反应。成功获得了纯化的CFP10蛋白,为进一步研究CFP10蛋白的致病机理提供了实验依据。     

降钙素基因相关肽衍生物的制备及降血压功能研究

用PCR法将人的降钙素基因相关肽(calcitonin gene related—peptide,CGRP)基因克隆到表达载体pGEX-4T-2的GST基因后,构建成一个新的表达质粒pGEX—CGRP．另外分别将2个有降压功能的小肽HHL和RPLKPW的基因克隆到CGRP基因后,构建成2个表达质粒pGEX—CGRP-3AA和pGEX—CGRP-6AA．将此3个表达质粒转化到大肠杆菌TG1中,获得3个高表达的融合蛋白：GST—CGRP,GST—CGRP—HHL,GST—CGRP—RPLKPW;通过G1utathione Sepharose 4B亲和层析纯化融合蛋白,测定蛋白浓度,利用自发性高血压大鼠(spontaneously hypertensive rat,SHR)来检测蛋白的降血压功能,发现融合蛋白GST—CGRP—HHL具有显著的降压效果,能使舒张压下降8．0kPa,且降压维持时间延长,达到70min以上．     

应用重组Etp28抗原免疫预防球虫病的研究

将构建好的可表达ＧＳＴ融合蛋白的重组病毒ＡｃＭＮＰＶ－ＯＣＣ－Ｅｔｐ２８感染Ｓｆ９细胞,７２ｈ后取感染了病毒的细胞裂解物上清液进行ＳＤＳ－ＰＡＧＥ和Ｗｅｓｔｅｍ－ｂｌｏｔ分析,结果显示５３ｋＤａ的融合蛋白在昆虫Ｓｆ９细胞中得到了高效表达,表达水平为占细胞总蛋白的２１．３％;将ＧＳＴ－６ｘＨｉｓ－Ｅｔｐ２８注射维菌鸡进行免疫保护试验,结果表明免疫组比对照组在平均增重和盲肠粘膜层卵囊计数方面有一定程度     

Structure of the dengue virus envelope protein after membrane fusion

Dengue virus enters a host cell when the viral envelope glycoprotein, E, binds to a receptor and responds by conformational rearrangement to the reduced pH of an endosome. The conformational change induces fusion of viral and host-cell membranes. A three-dimensional structure of the soluble E ectodomain (sE) in its trimeric, postfusion state reveals striking differences from the dimeric, prefusion form. The elongated trimer bears three 'fusion loops' at one end, to insert into the host-cell membrane. Their structure allows us to model directly how these fusion loops interact with a lipid bilayer. The protein folds back on itself, directing its carboxy terminus towards the fusion loops. We propose a fusion mechanism driven by essentially irreversible conformational changes in E and facilitated by fusion-loop insertion into the outer bilayer leaflet. Specific features of the folded-back structure suggest strategies for inhibiting flavivirus entry.     

食管癌相关基因2(ECRG2)包涵体的溶解与纯化

采用生物工程的手段,用插有食管癌相关基因2(ECRG2)开放阅读框(ORF)的原核表达质粒pEGX-4T-1转化大肠杆菌E.coli,诱导表达了重组的GST-ECRG2融合蛋白;收集GST-ECRG2融合蛋白包涵体,经SKL溶解后在PBS中透析复性,用GST亲和层析柱纯化,从而获得一定数量的高纯度重组ECRG2蛋白.     

Rab5 is a signalling GTPase involved in actin remodelling by receptor tyrosine kinases

Rab5 is a small GTPase involved in the control of intracellular trafficking, both at the level of receptor endocytosis and endosomal dynamics. The finding that Rab5 can be activated by receptor tyrosine kinases (RTK) raised the question of whether it also participates in effector pathways emanating from these receptors. Here we show that Rab5 is indispensable for a form of RTK-induced actin remodelling, called circular ruffling. Three independent signals, originating from Rab5, phosphatidylinositol-3-OH kinase and Rac, respectively, are simultaneously required for the induction of circular ruffles. Rab5 signals to the actin cytoskeleton through RN-tre, a previously identified Rab5-specific GTPase-activating protein (GAP). Here we demonstrate that RN-tre has the dual function of Rab5-GAP and Rab5 effector. We also show that RN-tre is critical for macropinocytosis, a process previously connected to the formation of circular ruffles. Finally, RN-tre interacts with both F-actin and actinin-4, an F-actin bundling protein. We propose that RN-tre establishes a three-pronged connection with Rab5, F-actin and actinin-4. This may aid crosslinking of actin fibres into actin networks at the plasma membrane. Thus, we have shown that Rab5 is a signalling GTPase and have elucidated the major molecular elements of its downstream pathway.