德国小蠊变应原Bla g 8的克隆表达及进化分析

通过5’-RACE获得德国小蠊变应原Bla g 8基因的全长cDNA序列,进行生物信息学分析,构建原核表达载体,诱导重组蛋白表达,建立系统进化树,为进一步研究奠定基础。通过5’-RACE技术,PCR扩增获取编码德国小蠊变应原Bla g 8蛋白的全长cDNA序列;采用生物信息学方法分析预测Bla g 8蛋白的信号肽、疏水性、跨膜区、二级结构、三级结构;建立系统进化树;构建原核表达载体pET32a-B8,IPTG诱导重组蛋白表达,并用His-tag抗体Western blotting验证。结果显示,获得编码德国小蠊变应原Bla g 8的全长cDNA序列,其完整阅读框含618个碱基,编码205个氨基酸。序列分析显示该蛋白,肌球蛋白轻链,具有EF手蛋白保守功能域。IPTG诱导获得重组蛋白。获得德国小蠊Bla g 8的完整cDNA序列,成功构建重组原核表达质粒pET32a-B8,并表达出融合蛋白。     

德国小蠊两个海藻糖合成酶基因的克隆、组织分布及温度诱导表达分析

【目的】海藻糖合成酶（trehalose-6-phosphate synthase, TPS）是参与昆虫血糖-海藻糖合成的关键酶。本研究旨在克隆德国小蠊 Blattella germanica TPS基因,研究TPS基因在德国小蠊不同组织中的表达模式及在不同温度处理下的表达情况。【方法】通过RACE技术克隆德国小蠊TPS基因全长序列,利用荧光定量PCR的方法检测TPS基因在德国小蠊5龄幼虫不同组织中的表达模式及在高温(40℃和46℃处理30 min)及低温(0℃和10℃处理1 h)逆境下的表达量变化。【结果】从德国小蠊中克隆获得2个TPS基因,分别命名为 BgTPS1 (GenBank登录号：KR050213) 和 BgTPS2 (GenBank登录号：KR050214)。其中,BgTPS1基因cDNA序列全长2 987 bp,开放阅读框 (ORF) 2 502 bp,编码833个氨基酸;BgTPS2基因cDNA序列全长3 212 bp,开放阅读框2 469 bp,编码822个氨基酸。BgTPS1和BgTPS2基因都主要在5龄幼虫脂肪体中表达,且BgTPS2基因的表达量为BgTPS1基因表达量的3.9倍。在两种不同极端温度诱导下,BgTPS1和BgTPS2基因mRNA均上调表达。其中,BgTPS2 的表达量始终显著高于 BgTPS1。在0℃时,BgTPS1和BgTPS2的表达量最高。【结论】德国小蠊5龄幼虫中存在2个TPS基因。两个TPS基因均在脂肪体中高表达,且BgTPS2基因的表达量显著高于BgTPS1基因;低温和高温诱导下均能促进两个基因的表达量上升。该结果为进一步明确昆虫海藻糖的合成途径及其在昆虫对温度逆境的反应中的作用研究奠定了基础。     

棉卷叶野螟泛素基因的克隆、序列分析及原核表达

本研究用RT-PCR方法,克隆了棉卷叶野螟Haritalodes derogata (Fabricius)泛素基因编码区,GenBank登录号为EU580145。序列分析表明,该编码区长228 bp,编码76个氨基酸,推测的编码蛋白的相对分子质量和等电点分别为8.53 kD和5.83。同源性比较发现,棉卷叶野螟泛素基因与其他10种昆虫泛素基因在氨基酸水平上具有93%以上的相似性。系统发育树显示棉卷叶野螟与斜纹夜蛾Spodoptera litura (Fabricius)遗传距离较近,通过同源建模获得了该棉卷叶野螟基因编码蛋白的理论三维结构。将棉卷叶野螟泛素基因与pET-32a(+)连接,构建原核表达载体pET-32a-ub,经IPTG诱导,棉卷叶野螟泛素基因在大肠杆菌BL21(DE3) 中高效表达。本研究成功克隆了棉卷叶野螟泛素基因的编码区,并经Western blotting分析证明实现了该基因的原核表达,为进一步研究其在该昆虫体内的作用机理奠定了基础。     

酚氧化酶参与德国小蠊对大肠杆菌的免疫应答

【目的】探讨酚氧化酶(phenoloxidase, PO)在德国小蠊Blattella germanica对大肠杆菌Escherichia coli的免疫响应中的作用。【方法】利用同源克隆和RACE方法获得德国小蠊酚氧化酶基因（BgPO）的全长cDNA序列,用MEGA5.1软件构建BgPO与其他昆虫PO的系统进化树,用RT-PCR方法检测BgPO的组织表达模式及大肠杆菌诱导后不同时间的表达量变化,用Hultmark 方法测定抑菌活力,用邻苯二酚法测定酚氧化酶活性。【结果】获得的德国小蠊BgPO基因（GenBank登录号：KJ789157）cDNA全长为2 252 bp,其中开放阅读框大小为2 085 bp,编码695个氨基酸,预测的分子量和等电点分别为79.7 kDa和6.19。Blast分析结果表明德国小蠊BgPO与其他昆虫PO有较高的同源性,其中与白蚁Coptotermes formosanus PO的氨基酸序列一致性高达80%;系统进化树分析显示其与C. formosanus PO的亲缘关系最近。基因表达检测结果表明BgPO主要在血淋巴细胞和表皮中表达。大肠杆菌诱导德国小蠊后,发现BgPO的表达量在诱导24 h后升高,在诱导后36 h达到峰值;其血淋巴的抑菌活力及酚氧化酶的活性在诱导后6-36 h内均随着诱导时间的增加而增加,且菌诱导组与PBS诱导组之间存在显著差异(P<0.05)。【结论】本研究获得的德国小蠊酚氧化酶基因BgPO主要在血淋巴和表皮中表达,并参与了大肠杆菌诱导的免疫应答反应。研究结果为进一步探索酚氧化酶在德国小蠊对病原菌的免疫响应机制奠定基础。     

甜菜夜蛾核多角体病毒泛素基因的克隆及原核表达

甜菜夜蛾核多角体病毒(Spotoptera exigua multi-nucleopolyhedrovirus,SeMNPV)泛素基因ubiquitin被克隆和序列分析,该基因编码区全长243bp,编码80个氨基酸残基,预计蛋白质分子量为9.4kDa.将这一ubiquitin基因克隆到原核表达载体pET-28a上,转化至BL21(DE3)中,用IPTG进行诱导表达,对表达的条件进行了优化.用异源的泛素单克隆抗体检测目的蛋白,Western blot实验证明所表达的蛋白是泛素蛋白.同时,我们制备了特异性的抗体,为以后的研究工作做了基础.通过计算机软件Gendoc对不同来源的泛素进行分析,结果显示,病毒中的泛素与真核细胞中的泛素相比较,泛素的氨基酸序列有较大的变化,杆状病毒的泛素基因在分子进化上可能有比较独特的途径.     

甜菜夜蛾核多角体病毒泛素基因的克隆及原核表达

甜菜夜蛾核多角体病毒（Spotoptera exigua multi-nucleopolyhedrovirus,SeMNPV)泛素基因ubiquitin被克隆和序列分析,该基因编码区全长243bp,编码80个氨基酸残基,预计蛋白质分子量为9.4kDa。将这一ubiquitin基因克隆到原核表达载体pET-28a上,转化至BL21（DE3）中,用IPTG进行诱导表达,对表达的条件进行优化,用异源的泛素单克隆抗体检测目的蛋白,Western blot 实验证明所表达的蛋白是泛素蛋白。同时,我们制备了特异性的抗体,为以后的研究工作做了基础,通过计算机软件Gendoc对不同来源的泛素进行分析,结果显示,病毒中的泛素与真核细胞中的泛素相比较,泛素的氨基酸序列有较大的变化,杆状病毒的深入素基因在分子进化上可能有比较独特的途径。     

德国小蠊Akirin基因的克隆及表达分析

Akirin基因是新近发现的在果蝇NF-κB依赖的Imd信号通路调控中不可或缺的转录因子。在除果蝇以外的昆虫中,Akirin基因是否参与Imd通路的调控,亦或对NF-κB依赖的Toll通路也有调控作用还未有报道。本研究旨在初步研究德国小蠊Blattella germanica中Akirin基因的基本特征、在不同组织中的表达模式及注射法RNAi实验对Akirin基因沉默效果,以期为Akirin基因功能的研究奠定基础。通过与已报道的其它昆虫的Akirin基因进行同源比对,利用RACE(rapid amplification of c DNA ends)技术,成功从德国小蠊中克隆到1个Akirin基因,该基因全长864 bp,开放阅读框(ORF)大小为543 bp,编码180个氨基酸。蛋白序列比对及进化树结果显示,Akirin基因有非常保守的核定位信号序列,且与内华达古白蚁Zootermopsis nevadensis的亲缘关系最近,同源性为86%。荧光定量PCR的结果表明Akirin基因在德国小蠊检测的4个组织中均有表达,但表达水平有差异,在血淋巴的表达水平最高,其次为脂肪体。通过注射法RNAi实验成功抑制了Akirin基因的表达水平,并且RNAi的效果随时间的延长而更强,在注射72 h后,Akirin基因m RNA的表达水平下降了90%。上述研究为Akirin基因的功能及德国小蠊防治研究提供了科学依据。     

牡丹泛素延伸蛋白基因片段的克隆及序列分析

目的：利用巢式PCR技术克隆牡丹泛素延伸蛋白基因,为泛素蛋白降解系统研究奠定基础,也为牡丹基因表达水平研究提供内参基因。方法：从牡丹（Paeonia suffruticosa）叶片、花瓣、花萼中提取总RNA,反转录得到cDNA,根据已报道的泛素延伸蛋白基因设计巢式引物进行PCR扩增。结果：得到一条389bp的牡丹泛素延伸蛋白基因片段,该片段编码129个氨基酸残基。结论：通过Blastn比对分析表明：牡丹泛素延伸蛋白基因与番茄、水稻、拟南芥等植物的泛素延伸蛋白基因一致性达到100%,编码的氨基酸序列同源性达94%以上。确认该片段即牡丹泛素延伸蛋白基因。     

德国小蠊几丁质酶基因的克隆及表达模式分析

几丁质酶广泛存在于自然界多个物种,其主要参与蜕皮、消化、防御与免疫等多项功能。本研究采用同源克隆结合RACE-PCR的方法,从德国小蠊中克隆到几丁质酶基因(Bg Chi)的c DNA全长序列(Gen Bank No:KJ789158)。Bg Chi全长为1881 bp,包含192 bp的3'非翻译区(UTR)和69 bp的5'UTR,其开放阅读框(ORF)为1620 bp,编码539个氨基酸。预测的相对分子量为59.7 k Da,理论等电点为5.0。Bg Chi具有几丁质酶典型的结构域:N-端信号肽,几丁质催化区,C-端几丁质结合区。系统进化树分析表明:Bg Chi与同翅目禾沫蝉Poophilus costalis的亲缘关系最近,为81%。组织分布表达显示,Bg Chi主要在表皮、中肠和气管组织有表达。定量PCR结果表明,Bg Chi在6龄蜕皮前表达量最高,随之下降到较低水平。本研究结果有助于提高我们对德国小蠊蜕皮发育机制的理解,也为从几丁质降解途径获取防治德国小蠊新方法奠定基础。     

桑泛素延伸蛋白基因片段的克隆及序列分析

目的:利用3’RACE技术克隆植物泛素基因,是进一步研究其功能的基础。方法:本研究从桑树(丰驰桑)(Morus bomby-cis)幼叶中提取总RNA,反转录成cDNA,根据已报道的泛素基因序列设计1条正向引物,利用3’RACE(Rapid Amplification of cDNAEnd)技术进行扩增。结果:扩增出1条690 bp的泛素基因片段。该片段5’端为编码156个氨基酸残基的阅读框,3’末端有219bp的非翻译区。结论:同源分析表明,此cDNA序列为泛素延伸蛋白基因(Genebank登录号为DQ839403)。用Genedoc软件对该片段编码的氨基酸序列进行同源性分析的结果表明:桑树泛素延伸蛋白与马铃薯、烟草、陆地棉、黄瓜的泛素延伸蛋白以及苜蓿的核糖体S27A蛋白的同源性都在96%以上。     

Ubiquitin genes in rainbow trout (Oncorhynchus mykiss)

Ubiquitin is a small protein involved in intracellular proteolysis. It is highly conserved throughout eukaryotic phyla and has been detected in such diverse species as yeast, barley, Drosophila and man. A previous study showed that chromatin of rainbow trout testis contains free ubiquitin with a sequence similar to that of other phyla. In the present study, which focused on rainbow trout but included eleven other species, it is shown that fish ubiquitin genetic organisation and expression are similar to those of other phylogenetic groups through the following set of observations: (a) Multiple loci were detected, (b) These loci encode repeats of ubiquitin, (c) Although the DNA sequences are not conserved, the encoded amino acid sequences are fully conserved, (d) The expression of ubiquitin was influenced by cell culture conditions and viral infection.     

家蝇泛素编码区 cDNA 序列的克隆及在原核细胞中的表达

泛素-蛋白酶体途径(ubiquitin-proteasome pathway)是具有高度选择性的蛋白质降解途径,该途径对细胞内蛋白的选择性降解起着重要作用。本研究根据 GenBank 已登录的真核生物泛素（ubiquitin）编码框的氨基酸序列,设计一对简并引物,RT-PCR 克隆了家蝇 Musca domestica 泛素基因的编码区 cDNA 序列,并进行了测序。序列分析表明,该编码区的长度为 228 bp,编码 76 个氨基酸,命名为 Mdubi ,GenBank 登录号为 DQ115796。同源性比较发现,Mdubi 氨基酸序列与其他真核生物泛素编码框同源性可达 94% 以上。RT-PCR 检测表明,Mdubi 在家蝇不同组织中均高效表达,且不受大肠杆菌 Escherichia coli 刺激的影响,是遍在性表达。为进一步研究 Mdubi 的结构和功能,将 Mdubi 克隆到原核表达载体 pQE30 上,构建重组质粒 pQE30-UBI,转化大肠杆菌 M15 感受态细胞,在 IPTG 诱导下进行了高效表达,SDS-PAGE 检测表明 Mdubi 在大肠杆菌中可表达相对分子质量为 9.6 kD 的可溶性融合蛋白;Western blot 分析表明表达产物能与 Ni-NTA 鏊合物特异性的结合,表明表达的 Mdubi 为 N 端带有 6His 标签的融合蛋白。利用 Ni²⁺-NTA 亲和柱一步纯化了 Mdubi,以该融合蛋白免疫新西兰大白兔制备了抗 Mdubi 血清。本研究成功克隆了家蝇泛素的编码序列,并在原核细胞中得到了表达,为进一步研究泛素在家蝇体内的作用机制奠定了基础。     

柞蚕核型多角体病毒泛素类似基因的克隆与序列分析

从感病的柞蚕Antheraea pernyi蛹中分离纯化柞蚕核型多角体病毒 (ApNPV),提取基因组DNA,分别构建ApNPV DNA的HindⅢ和SalⅠ酶切片段文库。对基因文库中1个克隆进行序列分析,得到1个长度为321 bp的序列,其中包含一个编码76个氨基酸的开放阅读框,预测的分子量为8.46 kD,系泛素类似基因。在读码框的上游调控序列中,具有典型的晚期基因启动子序列ataag。氨基酸序列同源性分析结果表明,ApNPV与黄杉毒蛾Orgyia pseudotsugata核型多角体病毒 (OpNPV)的同源性最高 (96.1%),与苜蓿尺蠖Autographa californica核型多角体病毒 (AcNPV) 的同源性为86.8%,与棉褐带卷蛾Adoxophyes orana 颗粒体病毒 (AoGV) 的同源性最低（71.1%）,但与人类、线虫和酵母的泛素同源性分别为77.6%、76.3%和76.3%。一些氨基酸残基在真核生物中保守,在杆状病毒中不保守,个别氨基酸残基是杆状病毒所特有的,这些氨基酸序列的改变对杆状病毒泛素基因的作用有待进一步研究。     

Core-directed protein design. II. Rescue of a multiply mutated and destabilized variant of ubiquitin.

We have applied the method described in the preceding paper [Finucane, M. D., et al. (1999) Biochemistry 38, 11604-11612], namely, stability-based selection using phage display, to explore the sequence requirements for packing in the hydrophobic core of ubiquitin. In contrast to the parent protein, which was a structurally compromised mutant, the selected variants could be overexpressed and purified in yields for structural studies. In particular, CD and NMR measurements showed that the selectants folded correctly to stable native-like structures. These points demonstrate the utility of our core-directed method for stabilizing and redesigning proteins. In addition and in contrast to foregoing studies on other proteins, which suggest that hydrophobic cores permit substitutions provided that hydrophobicity and core volumes are generally conserved, we find that the core of ubiquitin is surprisingly intolerant of amino acid substitutions; variants that survived our selection showed a clear consensus for the wild-type sequence. It is probable that our results differed from those from other groups for two reasons. First, ubiquitin may be unusual in that it has strict sequence requirements for its structure and stability. We discuss this result in light of sequence conservation in the eukaryotic ubiquitins and proteins of the ubiquitin structural superfamily. Second, our mutants were selected solely on the basis of stability, in contrast to the other studies that rely on function-based selection. The latter may lead to proteins that are more plastic and tolerant of substitutions.     

The Ubp6 family of deubiquitinating enzymes contains a ubiquitin-like domain: SUb.

A sequence motif that is Similar to Ubiquitin (SUb) has been identified in the Saccharomyces cerevisiae ubiquitin-specific protease Ubp6. SUb is conserved in all known Ubp6 homologues from a spectrum of eukaryotic species and is also present in a group of hypothetical proteins of unknown function (Unk1-3) present in sequence databases. An N-terminal deletion mutant of Ubp6 that lacks SUb is still capable of cleaving alpha-linked ubiquitin fusions, suggesting that SUb forms a separate domain to the catalytic core of Ubp6 and demonstrating that it is not required for in vitro cleavage activity. A homology model of the 78 N-terminal amino acids of human Ubp6, based on the known fold of ubiquitin, is presented. In human Ubp6, SUb shares only 20% sequence identity with ubiquitin. Even weaker similarity occurs between S. cerevisiae SUb and ubiquitin. The homology model supports a ubiquitin-like fold for SUb and suggests that two conserved Lys residues, corresponding to Lys48 and Lys63 of ubiquitin, are functionally important.     

Solution structure of ThiS and implications for the evolutionary roots of ubiquitin

ThiS is a sulfur carrier protein that plays a central role in thiamin biosynthesis in Escherichia coli. Here we report the solution NMR structure of ThiS, the first for this class of sulfur carrier proteins. Although ThiS shares only 14% sequence identity with ubiquitin, it possesses the ubiquitin fold. This structural homology, combined with established functional similarities involving sulfur chemistry, demonstrates that the eukaryotic ubiquitin and the prokaryotic ThiS evolved from a common ancestor. This illustrates how structure determination is essential in establishing evolutionary links between proteins in which structure and function have been conserved through eons of evolution despite loss of sequence identity. The ThiS structure reveals both hydrophobic and electrostatic surface features that are likely determinants for interactions with binding partners. Comparison with surface features of ubiquitin and ubiquitin homologs SUMO-1, RUB-1 and NEDD8 suggest how Nature has utilized this single fold to incorporate similar chemistry into a broad array of highly specific biological processes.     

The Shigella Type Three Secretion System Effector OspG Directly and Specifically Binds to Host Ubiquitin for Activation

The genus Shigella infects human gut epithelial cells to cause diarrhea and gastrointestinal disorders. Like many other Gram-negative bacterial pathogens, the virulence of Shigella spp. relies on a conserved type three secretion system that delivers a handful of effector proteins into host cells to manipulate various host cell physiology. However, many of the Shigella type III effectors remain functionally uncharacterized. Here we observe that OspG, one of the Shigella effectors, interacted with ubiquitin conjugates and poly-ubiquitin chains of either K48 or K63 linkage in eukaryotic host cells. Purified OspG protein formed a stable complex with ubiquitin but showed no interactions with other ubiquitin-like proteins. OspG binding to ubiquitin required the carboxyl terminal helical region in OspG and the canonical I44-centered hydrophobic surface in ubiquitin. OspG and OspG-homologous effectors, NleH1/2 from enteropathogenic E coli (EPEC), contain sub-domains I-VII of eukaryotic serine/threonine kinase. GST-tagged OspG and NleH1/2 could undergo autophosphorylation, the former of which was significantly stimulated by ubiquitin binding. Ubiquitin binding was also required for OspG functioning in attenuating host NF-κB signaling. Our data illustrate a new mechanism that bacterial pathogen like Shigella exploits ubiquitin binding to activate its secreted virulence effector for its functioning in host eukaryotic cells.     

Ubiquitin in stressed chicken embryo fibroblasts

Ubiquitin, a small 76-amino acid protein which is highly conserved in eukaryotic cells, occurs in several forms other than the free polypeptide. Among these are protein conjugates in which ubiquitin is covalently linked in lysylpeptide bond to lysl residues of other proteins and fusion proteins in which the amino-terminal domain is the precise ubiquitin sequence. Ubiquitin plays a role in cellular proteolytic degradation and in chromatin structure and has been postulated to be involved in the induction of a set of proteins which function during the cellular response to various kinds of environmental stress. We have measured the various forms of ubiquitin in cultures of chicken embryo fibroblasts under normal growth conditions and after treatment with a thermal or chemical stress. Levels of free ubiquitin fell slightly, ubiquitin conjugate levels rose shortly after stress began, and both then increased substantially as one of the cell's ubiquitin-encoding genes was activated by stress. The level of a protein synthesized as the carboxyl-terminal domain of one ubiquitin fusion protein was unchanged by a heat stress. The most dramatic effect was seen in the rapid disappearance of the ubiquitinated form of histone H2A, one of the major ubiquitin conjugates in cells in the interphase portion of their growth cycle. A significant rise in protein turnover was detected as a result of the stress, but occurred only when cells were removed from the stress condition. These results suggest that ubiquitin plays an important role both during and after stress, but fails to support hypotheses for ubiquitin and proteolysis in the activation of stress genes.     

Vitellogenin of Blattella germanica (L.) (Dictyoptera, blattellidae): nucleotide sequence of the cDNA and analysis of the protein primary structure

The cloning and sequencing of a cDNA of the vitellogenin gene from the cockroach Blattella germanica is reported. It is 5,749 nucleotides long and encodes an amino acid sequence of 1,862 residues (including a putative signal peptide of 17 residues). The vitellogenin sequence includes a long serine-rich stretch between amino acids 322 and 349, and two other stretches between amino acids 1691 and 1740. The vitellogenin of B. germanica shows a notable similarity (between 32 and 42%) to those described in other insects, and its alignment shows a high number of motifs conserved in all species, especially in the subdomains I-V. Non-parsimony methods (Neighbor Joining) of phylogenetic analysis of the insect vitellogenin sequences gave a tree showing a topology that is, in general, congruent with the currently accepted insect phylogenetic schemes. Arch.