IBV广东分离株GD05 S1基因的克隆、鉴定及其表达

鸡传染性支气管炎病毒(Infectious Brochitis virus,IBV)属于冠状病毒科冠状 病毒属,可引起鸡呼吸道、输卵管、肾脏、肠道及腺胃等多部位病变.近年来,由于新的I BV变异毒株不断出现,从而导致鸡传染性支气管炎病的不断爆发,造成严重的经济损失 [1, 2]}.IBV的基因组为单股RNA,主要编码3种主要结构蛋白:纤突蛋白(S)、膜蛋白(M) 和 核衣壳蛋白(N),其中S蛋白成熟裂解为S1和S2两个蛋白亚基.S1蛋白是IBV的主要免疫原 基因,可刺激机体产生中和抗体,决定病毒的组织亲嗜性,在病毒血清学分类中起主要作用 [1,3].     

鸡传染性支气管炎病毒E蛋白基因的表达

鸡传染性支气管炎(Infectious Bronchitis,IB)是由传染性支气管炎病毒(Infectious Bronchitis Virus,IBV)引起的鸡的一种急性、高度接触性传染病。该病是危害全球养禽业的重要传染病之一[1,2]。其感染的主要特征是气管啰音、咳嗽和打喷嚏?送猓?该病还可以引起蛋鸡产蛋量下降和蛋品质下降。雏鸡可由于呼吸道或肾脏的感染而死亡。虽然疫苗的使用对IB的流行起到了一定的预防和控制作用,但由于IBV血清型众多,不同血清型毒株之间具有较小的交叉保护性甚至无交叉保护性。因此,IB目前仍在免疫鸡群和非免疫鸡群发生和传播,给养禽业造成了严重…     

鸡传染性支气管炎病毒E蛋白基因的表达

鸡传染性支气管炎(Infectious Bronchitis,IB)是由传染性支气管炎病毒(Infectious Bronchitis Virus,IBV)引起的鸡的一种急性、高度接触性传染病.该病是危害全球养禽业的重要传染病之一[1,2].其感染的主要特征是气管啰音、咳嗽和打喷嚏.此外,该病还可以引起蛋鸡产蛋量下降和蛋品质下降.雏鸡可由于呼吸道或肾脏的感染而死亡.虽然疫苗的使用对IB的流行起到了一定的预防和控制作用,但由于IBV血清型众多,不同血清型毒株之间具有较小的交叉保护性甚至无交叉保护性.因此,IB目前仍在免疫鸡群和非免疫鸡群发生和传播,给养禽业造成了严重的经济损失.     

外源基因在大肠杆菌中表达研究进展

近年来,基因工程技术的迅速发展,大量有价值的蛋白质大肠杆菌中获得了高表达。多种表达系统的完善与发展,及蛋白质分离纯化技术的提高,异源蛋白的产量与纯度已不再是困扰人们的主要问题,人们开始更多地关注异源蛋白的活性,比活性及异源蛋白的正确性,完整性。随着这些问题的解决,重组蛋白的应用才能真正走向成熟。     

Plasmid complex of E. coli B-13

The plasmid complex was identified in a wild type strain B-13 of Escherichia coli. The complex was found to contain four conjugative R-plasmids / pAP24 -1 fi+, pAP24 -2 fi-, pAP24 -3 fi-, pAP24 -4 fi-/, one conjugative Col-plasmid / pAP24 -5/ and one conjugative F-like plasmid Ent/ pAP10 -2 fi+/. The molecular weight of pAP24 -1 is 53.6 X 10(6), pAP24 -2 - 40.9 X 10(6), pAP24 -3 - 73.8 X 10(6), pAP24 -4 - 51,3 X 10(6). It is suggested that an autonomous transfer factor exists in the plasmid complex.     

草木樨状黄芪变异系中甲硫氨酸代谢相关cDNA的分子克隆及其在大肠杆菌中的表达

利用mRNA差异显示技术(differential display)从草木樨状黄芪耐甲硫氨酸变异系中分离到一差异cDNA片段,命名为tm03(360bp)。mRNA杂交结果显示,该片段只在变异苗中表达,初步确定其与甲硫氨酸代谢相关。测序后在Genebank搜寻,未发现有同源序列。进一步分析表明,该cDNA克隆可编码完整的蛋白。在该基因片段两端分别合成含HindⅡ和BamH Ⅰ酶切位点的引物,用PCR扩增后亚克隆到pRSET A表达载体,转化宿主菌JMl09(DE3),经IPTG诱导表达了N′端含6个组氨酸的蛋白质,分子量约为14kD,为进一步研究该蛋白的结构和生物学功能奠定基础。     

Stringent control of protein synthesis in E. coli

The effect of ppGpp on the rate of protein synthesis has been determined in vivo. When the stringent response is triggered and then reversed in isogenic strains carrying either spoT^? or spoT⁺, the mutants lower their elevated ppGpp only slowly, whereas wild type cells do so rapidly. Protein synthesis resumes only after a lag in spoT^? cells but almost immediately in spoT⁺ cells. In spoT^?rel^? double mutants, ppGpp does not accumulate under these conditions and protein synthesis resumes immediately. Inhibition of protein synthesis in spoT^?rel⁺ cells therefore appears to be due to elevation of ppGpp levels and not to any other effect of the spoT^? mutation.     

An assessment of neural network and statistical approaches for prediction of E. coli promoter sites.

We have constructed a perceptron type neural network for E. coli promoter prediction and improved its ability to generalize with a new technique for selecting the sequence features shown during training. We have also reconstructed five previous prediction methods and compared the effectiveness of those methods and our neural network. Surprisingly, the simple statistical method of Mulligan et al. performed the best amongst the previous methods. Our neural network was comparable to Mulligan's method when false positives were kept low and better than Mulligan's method when false negatives were kept low. We also showed the correlation between the prediction rates of neural networks achieved by previous researchers and the information content of their data sets.     

Negative control of the galactose operon in E. coli

Summary Non-inducible mutants have been isolated which synthesize the three galactose enzymes with the basal rate both in the absence and in the presence of inducers. These mutations are closely linked to the lysA gene, as are the constitutive mutations in the regulator gene first described by Buttin (1963).The non-inducible mutants are Gal ^– on EMB gal plates. Revertants to the Gal ⁺ phenotpye are constitutive. Heterozygotes have been prepared at the locus of the regulator gene (galR), abd dominance studies involving the different alleles at this locus have been carried out. The non-inducible mutations are dominant over the wildtype, and this in turn is dominant over constitutive mutations in the galR gene.Starting from the non-inducible mutations, deletions have been isolated, which extend from the galR gene into the lysA gene. These are constitutive.The behavior of the non-inducible mutations and of the deletions are strong arguments for negative control of the galactose operon.     

A genetic approach to characterizing complex promoters in E. coli

The chromosomal distributions of five families of mouse r-protein genes (S16, L18, L19, L30 and L32/33) were studied by Southern blot analysis of DNA from a panel of mouse-hamster hybrid cells containing various complements of mouse chromosomes. Our results indicated that members of a particular family are often located on more than one chromosome, that extensive clustering of many r-protein gene families on a few chromosomes is unlikely, and that there is no obligatory linkage of r-protein and rRNA genes.     

Allosteric control of quaternary states in E. coli aspartate transcarbamylase

Changes in the molecular dimensions of ATCase in the unligated T-state are an increase of 0.4 A in the separation of catalytic trimers when ATP binds. When the R-state is produced by binding of phosphonoacetamide and malonate, addition of CTP or CTP + UTP decreases the separation of catalytic trimers by 0.5 A. In the unliganded Glu239----Gln mutant, in which the T-state is destabilized so that the enzyme exists in an intermediate quaternary state, ligation of ATP transforms the mutant enzyme to the R-state, whereas CTP converts this enzyme to the T-state. Thus, this mutant is much more sensitive to heterotropic allosteric control than is the native enzyme. In this communication we propose a preliminary model based on new crystallographic results that heterotropic regulation occurs partly through control of the quaternary structure by these effectors, thus regulating catalysis.     

Orientational control is an efficient control mechanism for phase switching in the E. coli fim system

The fim system in E. coli controls the expression of type-1 fimbriae. These are hair-like structures that can be used to attach to host cells. Fimbriation is controlled by a mechanism called "orientational control." We present two families of models for orientational control to understand the details of how it works. We find that the main benefits of orientational control are that (i) it allows rapid adjustment of fimbriation levels in response to a change of environmental conditions while (ii) keeping the overall frequencies with which a cell switches between the fimbriate state and the afimbriate state low. The main reason for the efficiency of orientational control in regulation of fimbriation levels is that it keeps the system far from its steady state.     

Modulation of the immune response by Middle East respiratory syndrome coronavirus

Coronavirus (CoV) infections are commonly associated with respiratory and enteric disease in humans and animals. In 2012, a new human disease called Middle East respiratory syndrome (MERS) emerged in the Middle East. MERS was caused by a virus that was originally called human coronavirus-Erasmus Medical Center/2012 but was later renamed as Middle East respiratory syndrome coronavirus (MERS-CoV). MERS-CoV causes high fever, cough, acute respiratory tract infection, and multiorgan dysfunction that may eventually lead to the death of the infected individuals. The exact origin of MERS-CoV remains unknown, but the transmission pattern and evidence from virological studies suggest that dromedary camels are the major reservoir host, from which human infections may sporadically occur through the zoonotic transmission. Human to human transmission also occurs in healthcare facilities and communities. Recent studies on Middle Eastern respiratory continue to highlight the need for further understanding the virus-host interactions that govern disease severity and infection outcome. In this review, we have highlighted the major mechanisms of immune evasion strategies of MERS-CoV. We have demonstrated that M, 4a, 4b proteins and Plppro of MERS-CoV inhibit the type I interferon (IFN) and nuclear factor-κB signaling pathways and therefore facilitate innate immune evasion. In addition, nonstructural protein 4a (NSP4a), NSP4b, and NSP15 inhibit double-stranded RNA sensors. Therefore, the mentioned proteins limit early induction of IFN and cause rapid apoptosis of macrophages. MERS-CoV strongly inhibits the activation of T cells with downregulation of antigen presentation. In addition, uncontrolled secretion of interferon ɣ-induced protein 10 and monocyte chemoattractant protein-1 can suppress proliferation of human myeloid progenitor cells.     

Excess capacity of H(+)-ATPase and inverse respiratory control in Escherichia coli.

With succinate as free-energy source, Escherichia coli generating virtually all ATP by oxidative phosphorylation might be expected heavily to tax its ATP generating capacity. To examine this the H(+)-ATPase (ATP synthase) was modulated over a 30-fold range. Decreasing the amount of H(+)-ATPase reduced the growth rate much less than proportionally; the H(+)-ATPase controlled growth rate by < 10%. This lack of control reflected excess capacity: the rate of ATP synthesis per H(+)-ATPase (the turnover number) increased by 60% when the number of enzymes was decreased by 40%. At 15% H(+)-ATPase, the enzyme became limiting and its turnover was increased even further, due to an increased driving force caused by a reduction in the total flux through the enzymes. At smaller reductions of [H(+)-ATPase] the total flux was not reduced, revealing a second cause for increased turnover number through increased membrane potential: respiration was increased, showing that in E.coli, respiration and ATP synthesis are, in part, inversely coupled. Indeed, growth yield per O2 decreased, suggesting significant leakage or slip at the high respiration rates and membrane potential found at low H(+)-ATPase concentrations, and explaining that growth yield may be increased by activating the H(+)-ATPase.