猪链球菌2型甲基受体趋化蛋白编码基因05SSU0273的原核表达及纯化

目的 原核表达猪链球菌2型甲基受体趋化蛋白编码基因05SSU0273。方法 通过PCR方法检测该基因在不同血清型猪链球菌中的分布情况,然后利用获得的猪链球菌2型05SSU0273基因片段, 构建重组表达载体pET32a::05SSU0273。将质粒转入E. coli BL21中,经IPTG诱导,SDS-PAGE和Western blot实验证实目的基因的表达, 然后以His亲和层析柱纯化重组蛋白。结果 在S. suis 2 35个血清型标准株中,有20株分离株扩增出目的条带。重组质粒可在宿主菌中高效表达,经镍柱亲和层析得到相对分子质量为43 kD的重组蛋白。结论 本实验成功获得S. suis 2 MCP蛋白,为研究其在猪链球菌2型致病过程中发挥的作用奠定了基础。     

2型猪链球菌表面蛋白Sao的生物信息学分析及基因工程疫苗的设计

目的利用生物信息学方法分析Sao蛋白结构并预测B细胞抗原表位,筛选可用于疫苗设计的序列。方法以Sao蛋白的氨基酸序列为基础,利用Protparam工具分析蛋白基本理化性质,TMHMM预测跨膜区,PredictProtein在线分析蛋白二级结构,SWISS-MODEL软件模拟三级空间构象,DNASTAR分析亲(疏)水性、可塑性和表面可及性,综合使用在线ABCPred和BepiPred工具预测B细胞抗原表位,筛选能用于构建基因工程疫苗的蛋白序列。结果 Sao蛋白羧基端存在7个高度一致的重复序列以及1个LPVTG保守膜锚定基序,二级结构组分中无规卷曲比例高达74.21%,三级空间构象模拟结果与二级结构预测一致。蛋白的亲水区域、可塑性区域、表面可及性区域比例分别为76.21%、64.06%和75.04%。Sao存在多个线性抗原表位,经筛选得到两个可用于疫苗设计的蛋白序列,BLAST显示这两个序列为猪链球菌所特有,存在于2型猪链球菌9种不同的分离菌株中,同时也存在于猪链球菌致病性血清型1、2、1/2、3、7、9、14型中。结论 Sao蛋白为不稳定蛋白,亲水性强,筛选得到的两个蛋白序列抗原性强且高度保守,为猪链球菌特有序列,能够用于基因工程疫苗的构建。     

猪链球菌2型福建分离株的主要毒力基因分析

目的为了解福建地区猪链球菌2型菌株毒力因子分布情况。方法选取谷氨酸脱氢酶(gdh)、荚膜多糖(cps)、溶菌酶释放蛋白(mrp)、胞外因子(ef)、溶血素(sly)、纤连蛋白/血纤蛋白原结合蛋白(fbps)及毒力相关序列orf2等7个猪链球菌2型主要毒力基因,分别设计了7对引物,采用PCR方法,对本室分离保存的猪链球菌2型福建分离株的毒力基因进行分析。结果从屠宰生猪体内分离的4个猪链球菌2型菌株和SS2PFJ07株基因型为gdh+/cps2J+/mrp+/ef-/sly-/fb-ps+/orf2+,另1株从生猪体内分离的分离菌株基因型为gdh+/cps2J+/mrp+/ef+/sly+/fbps+/orf2+。结论福建地区生猪中猪链球菌2型至少有两种毒力基因型。     

2型猪链球菌层粘连蛋白结合蛋白的原核表达及免疫原性检测

目的表达2型猪链球菌（Streptococcus suis2,S.suis2）层粘连蛋白结合蛋白（Lmb）并检测其免疫原性。方法 PCR检测lmb基因在不同血清型S.suis中的分布。将S.suis2中国强毒株05ZYH33的lmb基因克隆至表达载体pET32a,转化大肠杆菌E.coliBL21,IPTG诱导表达,His亲和层析柱纯化重组蛋白。Western blot检测Lmb的免疫原性。结果 lmb基因存在于大多数S.suis血清型中。诱导表达并纯化后获得较高纯度的重组蛋白。重组Lmb能够和感染05ZYH33全菌的猪恢复期血清反应。结论 lmb基因在S.suis不同血清型中广泛分布,Lmb在细菌感染宿主过程中表达,可以作为疫苗开发的候选分子。     

湖北钉螺髓样分化因子88的鉴定及其在抗血吸虫感染固有免疫中的地位

目的克隆、鉴定湖北钉螺(Oncomelania hupensis)髓样分化因子88(MyD88)基因,并通过观察感染日本血吸虫前后钉螺各组织中MyD88 m RNA表达水平的变化,探讨其在抗血吸虫感染固有免疫中的地位。方法通过c DNA末端快速扩增技术(Rapid amplification of c DNA ends,RACE)获取湖北钉螺MyD88全长c DNA序列,预测其蛋白结构域,并进行多序列比对及保守区域分析,构建系统进化树。使用实时荧光定量PCR(Real-time quantitative PCR,RT-q PCR)技术检测MyD88基因在血吸虫感染前后钉螺各组织中的表达变化。结果湖北钉螺MyD88全长c DNA开放阅读框(Open reading frame,ORF)1 406 bp,编码468个氨基酸,蛋白N端和C端分别存在死亡结构域和TIR(Toll/interlrukin-1 receptor,TIR)结构域。与其他软体类MyD88氨基酸序列比对,相似性为38%~52%;系统进化树提示钉螺MyD88和光滑双脐螺MyD88起源于共同的祖先基因。q PCR结果显示,检测的所有组织中均有MyD88 m RNA的表达,其中血淋巴细胞中表达最为丰富。感染日本血吸虫后,除钉螺头足外,MyD88 m RNA在肝脏、生殖腺、血淋巴细胞等组织中均有上调表达,以血淋巴细胞中上调表达最显著。结论湖北钉螺存在依赖MyD88的TLRs(Toll-like receptors,TLRs)信号通路,MyD88分子可能在钉螺对抗日本血吸虫感染的固有免疫中发挥重要作用。     

猪链球菌2型四川人源分离株ZYH18纤连蛋白结合蛋白基因的克隆和序列分析

目的对2005年猪链球菌2型（Streptococcus suis type 2，S．suis 2）四川资阳人源分离株ZYH18纤连蛋白结合蛋白（FBPS）基因进行克隆和序列分析。方法以ZYH18的基因组DNA为模板，采用PCR方法扩增出纤连蛋白／血纤蛋白原结合蛋白基因片段，克隆于pMD-T18栽体，构建成载体pMD-T—fbps，转化到宿主菌TG1中，进行序列测定（GenBank登录号为DQ345444）。测序结果与实验室保存的其它7株猪链球菌2型临床分离菌株测序结果及GenBank提交序列AF438158进行编码区基因的同源性比对。结果成功克隆了实验室保存的分离于不同时间和地点的，包括ZYH18在内的8株S．suis2临床分离菌株的．朋加基因，并对其编码区基因进行了同源性比对。结论实验室保存的8株菌的FBPS编码区基因同源性高达100％，并不因分离时间和地点的不同而不同；与GenBank提交序列AF438158同源性为99％，存在两个氨基酸的差异。     

浙江省人源猪链球菌鉴定及毒力基因检测分析

目的 鉴定浙江省2005-2020年散发猪链球菌感染者分离株血清型并检测其毒力基因,了解该地区临床致病株毒力基因的分布情况与分子流行病学特征。方法 收集猪链球菌感染者临床分离株,采用传统细菌学方法及基质辅助激光解吸电离飞行时间质谱(MALDI TOF MS)鉴定的同时,利用聚合酶链(PCR)技术检测其链球菌属(tuf)、猪链球菌种(16S rRNA)、猪链球菌7型(Cps7H)、猪链球菌9型(Cps9D)与2型猪链球菌(Cps2J)/兼荚膜毒力基因以及毒力基因:溶菌酶释放蛋白(mrp)、胞外因子(epf)、溶血素(sly)、毒力相关序列(orf2)、纤连蛋白(fbps)、谷氨酸脱氢酶(gdh)、3-磷酸甘油醛脱氢酶(gapdh)等24种毒力基因携带情况。结果 28株人源分离株经综合鉴定均为2型猪链球菌,毒力基因群检测结果显示,除salKR毒力基因以及1株ZJ-31菌株外,96.43% (27/28) 的菌株均携带23种毒力基因;16S rRNA基因测序构建系统发育树,结果显示除来自2018年的ZJ-31菌株单独在另一分枝外,其它菌株同源性极高均在同一分枝。结论 浙江省十几年来散发猪链球菌病的人源分离株大多为2型猪链球菌强毒力株,遗传进化显示近年来已出现个别不同来源分枝群菌株。     

浙江省9株猪链球菌2型分离株Cps2J全基因克隆与序列分析

目的了解浙江猪链球菌2型(SS2)分离株的分子基础及与国内外其他分离株的基因差异程度,确定Cps2J基因变异位点和频率,为该地区的猪链球菌防治提供科学依据。方法提取菌株DNA,应用聚合酶链反应(PCR)扩增菌株Cps2J基因全片段,克隆入质粒载体,纯化后采用ABI自动测序仪测定序列,并同国内外其他分离株的基因进行比较。结果扩增出9株菌株的Cps2J基因的完整开放阅读框(ORF)都为999bp,编码333个氨基酸,9株菌株Cps2J片段核苷酸高度同源,同源性在99.7%～100%;与国内外其他的SS2核苷酸的同源性为98.8%～99.0%,与猪链球菌1型的同源性只有56.8%～57.0%。结论9株浙江省猪链球菌2型分离株Cps2J基因序列非常保守,这些不同来源的菌株可能有相同的起源。     

珠江口西岸地区致病性猪链球菌的分离鉴定及血清型分析

摘要：目的 调查目前流行于国内的4个主要致病性猪链球菌血清型在珠江口西岸地区的分布情况,从而进行有效的流行病学风险评估。方法 从珠江口西岸及附近地区的21个规模化猪场内疑似猪链球菌发病猪中采集病料,做细菌分离培养,对疑似猪链球菌分离培养阳性的168个菌株采用多重PCR方法作鉴定及血清型分析。结果 共检测到61株致病性猪链球菌,分布于12个区县,其中2型19株,1型3株,7型2株,9型未检测到,阳性率分别为31%、4.9%、3.3%和0。结论 珠江口西岸地区猪链球菌流行广泛,并以2型流行为主,其它血清型并存,存在较大的动物防疫和公共卫生风险。     

猪链球菌基因芯片检测方法的研究

目的建立猪链球菌基因芯片检测方法,实现对猪链球菌种、致病血清型及毒力相关基因的同步检测和鉴定。方法根据GenBank中猪链球菌的相关序列,设计并合成探针,采用点样法制备芯片;检测样本基因组DNA标记后与基因芯片杂交,激光扫描检测信号。结果检测结果显示,针对猪链球菌种、主要致病血清型及主要毒力相关基因设计的寡核苷酸探针可特异地识别对应靶基因,重复性好;而针对不同菌株设计的株特异性探针未获得预期检测效果。结论初步建立猪链球菌基因芯片检测体系,敏感性与特异性高,对于高通量鉴定猪链球菌菌种及其毒力有重要价值。     

用生物信息学方法预测2型猪链球菌98HAH33细胞壁结合蛋白

目的为预测已公布基因组序列的2型猪链球菌(SS2)98HAH33株的细胞壁结合蛋白,以研究它们在SS2致病过程中的作用。方法首先从GenBank获取由SS28HAH33基因组推测蛋白质氨基酸序列,然后根据分选酶底物的结构特征,采用"三部分模式"法鉴别分选酶底物;采用手动方法寻找在具有I型信号肽的蛋白质中具有LysM域、WxL域、胆碱结合域、GW域或S层同源域的蛋白质;利用InterProScan和BlastP服务器,对鉴定的蛋白质进行功能分析。结果共预测出9种分选酶底物,2种具有LysM域的蛋白。YP_001201232、YP_001201531和YP_001201656等3种已证实位于SS2菌体表面;其中YP_001201232为已知毒力因子OSF。另外4种蛋白质的功能分析表明,YP_001201484为糖苷酶,YP_001201544为枯草杆菌素样丝氨酸酶,YP_001199825和YP_001199755可能结合H因子,可能为新的毒力因子。YP_001200959、和YP_001201233等2种功能未知。结论提示SS2的多数分选酶底物可能为SS2的毒力因子,与致病过程相关。     

gdh基因在猪链球菌中的分布及重组GDH的抗原性研究

目的了解谷氨酸脱氢酶基因(gdh)在不同血清型猪链球菌(S.suis)中的分布情况,分析重组谷氨酸脱氢酶(GDH)的抗原性,为其应用于S.suis感染诊断和疫苗研究提供实验数据。方法应用PCR方法检测不同血清型S.suis中的gdh;利用45 kD重组GDH制备多克隆抗体,Western blot方法分析S.suis各血清型菌株与多克隆抗体的反应以及实验感染S.suis2型的猪血清与重组GDH的反应情况。结果在S.suis35个血清型标准株中,除了22、26、27、29、32及34型以外,其余包括1、2、1/2、7、9和14型在内的29个血清型、61株国内外S.suis2型分离株全部扩增出目的条带。用重组GDH免疫小鼠,在小鼠血清中均检测到抗GDH的抗体;Western blot结果显示,全部被检菌株与抗GDH血清反应均有单一特异性反应条带,6份实验感染猪血清均能与重组GDH产生反应条带。结论重组GDH具有免疫原性和反应原性,该蛋白有可能作为建立诊断试验的候选抗原,为进一步开展相关的血清学诊断方法和疫苗研究奠定基础。     

Identification of residues that control specific binding of the Shc phosphotyrosine-binding domain to phosphotyrosine sites.

The Shc adaptor protein contains two phosphotyrosine [Tyr(P)]binding modules--an N-terminal Tyr(P) binding (PTB) domain and a C-terminal Src homology 2 (SH2) domain. We have compared the ability of the Shc PTB domain to bind the receptors for nerve growth factor and insulin, both of which contain juxtamembrane Asn-Pro-Xaa-Tyr(P) motifs implicated in PTB binding. The Shc PTB domain binds with high affinity to a phosphopeptide corresponding to the nerve growth factor receptor Tyr-490 autophosphorylation site. Analysis of individual residues within this motif indicates that the Asn at position -3 [with respect to Tyr(P)], in addition to Tyr(P), is critical for PTB binding, while the Pro at position -2 plays a less significant role. A hydrophobic amino acid 5 residues N-terminal to the Tyr(P) is also essential for high-affinity binding. In contrast, the Shc PTB domain does not bind stably to the Asn-Pro-Xaa-Tyr(P) site at Tyr-960 in the activated insulin receptor, which has a polar residue (Ser) at position -5. Substitution of this Ser at position -5 with Ile markedly increased binding of the insulin receptor Tyr-960 phosphopeptide to the PTB domain. These results suggest that while the Shc PTB domain recognizes a core sequence of Asn-Pro-Xaa-Tyr(P), its binding affinity is modulated by more N-terminal residues in the ligand, which therefore contribute to the specificity of PTB-receptor interactions. An analysis of residues in the Shc PTB domain required for binding to Tyr(P) sites identified a specific and evolutionarily conserved Arg (Arg-175) that is uniquely important for ligand binding and is potentially involved in Tyr(P) recognition.     

Differential activation of yeast adenylyl cyclase by Ras1 and Ras2 depends on the conserved N terminus.

Although both Ras1 and Ras2 activate adenylyl cyclase in yeast, a number of differences can be observed regarding their function in the cAMP pathway. To explore the relative contribution of conserved and variable domains in determining these differences, chimeric RAS1-RAS2 or RAS2-RAS1 genes were constructed by swapping the sequences encoding the variable C-terminal domains. These constructs were expressed in a cdc25ts ras1 ras2 strain. Biochemical data show that the difference in efficacy of adenylyl cyclase activation between the two Ras proteins resides in the highly conserved N-terminal domain. This finding is supported by the observation that Ras2 delta, in which the C-terminal domain of Ras2 has been deleted, is a more potent activator of the yeast adenylyl cyclase than Ras1 delta, in which the C-terminal domain of Ras1 has been deleted. These observations suggest that amino acid residues other than the highly conserved residues of the effector domain within the N terminus may determine the efficiency of functional interaction with adenylyl cyclase. Similar levels of intracellular cAMP were found in Ras1, Ras1-Ras2, Ras1 delta, Ras2, and Ras2-Ras1 strains throughout the growth curve. This was found to result from the higher expression of Ras1 and Ras1-Ras2, which compensate for their lower efficacy in activating adenylyl cyclase. These results suggest that the difference between the Ras1 and the Ras2 phenotype is not due to their different efficacy in activating the cAMP pathway and that the divergent C-terminal domains are responsible for these differences, through interaction with other regulatory elements.     

The N-terminal region of the human immunodeficiency virus envelope glycoprotein gp120 contains potential binding sites for CD4.

Human immunodeficiency virus (HIV) vaccines targeted at blocking HIV-CD4 interactions are expected to be less affected by the sequence heterogeneity of HIV than those targeted at variable regions of the envelope outercoat glycoprotein, gp120. All potential CD4 binding sites identified thus far in HIV are localized in the C-terminal region of gp120. In this study we demonstrate that the N-terminal region of gp120 also contains conserved residues critical for binding to CD4 and that gp120-CD4 interactions can be blocked by an antiserum with binding specificity to an N-terminal region of gp120. These results suggest that not all potential CD4 binding sites are present in the C-terminal region of gp120 and that an alternative HIV vaccine development strategy may have to include the N-terminal gp120 region as a component to raise effective CD4-blocking antibodies.     

Role of the J-domain in the cooperation of Hsp40 with Hsp70

The Escherichia coli Hsp40 DnaJ and Hsp70 DnaK cooperate in the binding of proteins at intermediate stages of folding, assembly, and translocation across membranes. Binding of protein substrates to the DnaK C-terminal domain is controlled by ATP binding and hydrolysis in the N-terminal ATPase domain. The interaction of DnaJ with DnaK is mediated at least in part by the highly conserved N-terminal J-domain of DnaJ that includes residues 2–75. Heteronuclear NMR experiments with uniformly ¹⁵N-enriched DnaJ2–75 indicate that the chemical environment of residues located in helix II and the flanking loops is perturbed on interaction with DnaK or a truncated DnaK molecule, DnaK2–388. NMR signals corresponding to these residues broaden and exhibit changes in chemical shifts in the presence of DnaK(MgADP). Addition of MgATP largely reversed the broadening, indicating that NMR signals of DnaJ2–75 respond to ATP-dependent changes in DnaK. The J-domain interaction is localized to the ATPase domain of DnaK and is likely to be dominated by electrostatic interactions. The results suggest that the J-domain tethers DnaK to DnaJ-bound substrates, which DnaK then binds with its C-terminal peptide-binding domain.     

Three-dimensional structure of the adenine-specific DNA methyltransferase M.Taq I in complex with the cofactor S-adenosylmethionine.

The Thermus aquaticus DNA methyltransferase M.Taq I (EC 2.1.1.72) methylates N6 of adenine in the specific double-helical DNA sequence TCGA by transfer of --CH3 from the cofactor S-adenosyl-L-methionine. The x-ray crystal structure at 2.4-A resolution of this enzyme in complex with S-adenosylmethionine shows alpha/beta folding of the polypeptide into two domains of about equal size. They are arranged in the form of a C with a wide cleft suitable to accommodate the DNA substrate. The N-terminal domain is dominated by a nine-stranded beta-sheet; it contains the two conserved segments typical for N-methyltransferases which form a pocket for cofactor binding. The C-terminal domain is formed by four small beta-sheets and alpha-helices. The three-dimensional folding of M.Taq I is similar to that of the cytosine-specific Hha I methyltransferase, where the large beta-sheet in the N-terminal domain contains all conserved segments and the enzymatically functional parts, and the smaller C-terminal domain is less structured.     

Domain structure and dynamics in the helical filaments formed by RecA and Rad51 on DNA

Both the bacterial RecA protein and the eukaryotic Rad51 protein form helical nucleoprotein filaments on DNA that catalyze strand transfer between two homologous DNA molecules. However, only the ATP-binding cores of these proteins have been conserved, and this same core is also found within helicases and the F1-ATPase. The C-terminal domain of the RecA protein forms lobes within the helical RecA filament. However, the Rad51 proteins do not have the C-terminal domain found in RecA, but have an N-terminal extension that is absent in the RecA protein. Both the RecA C-terminal domain and the Rad51 N-terminal domain bind DNA. We have used electron microscopy to show that the lobes of the yeast and human Rad51 filaments appear to be formed by N-terminal domains. These lobes are conformationally flexible in both RecA and Rad51. Within RecA filaments, the change between the "active" and "inactive" states appears to mainly involve a large movement of the C-terminal lobe. The N-terminal domain of Rad51 and the C-terminal domain of RecA may have arisen from convergent evolution to play similar roles in the filaments.