辣根过氧化物酶在水相胶束中的动力学

研究了辣根过氧化物酶在三种表面活性剂（ＳＤＳ,ＴｒｉｔｏｎＸ－１００及ＣＴＡＢ）的水相胶束中催化联苯胺聚合反应的动力学。结果表明水相胶束体系有利于反应的进行。辣根过氧化物酶在水相胶束体系中遵循米氏反应,Ｋ_ｍ在ＳＤＳ、ＴｒｉｔｏｎＸ－１００及ＣＴＡＢ三种体系中分别为３．０１４×１０~（－４）ｍｏｌ／Ｌ、１．７２８×１０~（－４）ｍｏｌ／Ｌ和５．６６４×１０~（－５）ｍｏｌ／Ｌ。由于微环境的不同,ＨＲＰ在三种体系中表现出不同的最适反应温度和最适ｐＨ。     

Crystal structure of a novel fold protein Gp72 from the freshwater cyanophage Mic1

Cyanophages, widespread in aquatic systems, are a class of viruses that specifically infect cyanobacteria. Though they play important roles in modulating the homeostasis of cyanobacterial populations, little is known about the freshwater cyanophages, especially those hypothetical proteins of unknown function. Mic1 is a freshwater siphocyanophage isolated from the Lake Chaohu. It encodes three hypothetical proteins Gp65, Gp66, and Gp72, which share an identity of 61.6% to 83%. However, we find these three homologous proteins differ from each other in oligomeric state. Moreover, we solve the crystal structure of Gp72 at 2.3 Å, which represents a novel fold in the α + β class. Structural analyses combined with redox assays enable us to propose a model of disulfide bond mediated oligomerization for Gp72. Altogether, these findings provide structural and biochemical basis for further investigations on the freshwater cyanophage Mic1.     

幽门螺杆菌细胞毒素相关蛋白A对人胃腺癌上皮AGS细胞蛋白质组的影响

为明确幽门螺杆菌细胞毒素相关蛋白A(CagA)在致病过程中对宿主细胞蛋白质表达的影响及其与CagA磷酸化的相关性,分别用野生型cagA质粒和磷酸化位点突变型cagA质粒转染人胃腺癌上皮AGS细胞,应用表面加强激光解析电离-飞行时间质谱技术,分析细胞蛋白质组的改变。结果表明,在可捕获的400多个蛋白质中,野生型CagA可使AGS细胞质荷比为4229、4714、4728、5129、6546、6657、8162、9084、13803、14021的10个蛋白质表达上调,质荷比为2013、4286、8563、9952、11085、11645的6个蛋白质表达下调。突变型CagA只能使质荷比为4714、4728、6546和6657的蛋白质表达上调。这些结果提示,这16个差异表达蛋白质可能参与了CagA的致病过程,其中质荷比为4714、4728、6546和6657蛋白质表达的改变与CagA的磷酸化作用无关,而其余12个蛋白质表达的改变则都依赖于CagAEPIYA重复序列酪氨酸位点的磷酸化。这些发现为进一步探讨CagA的致病机制提供了实验依据。     

Upregulated MicroRNA-92b Regulates the Differentiation and Proliferation of EpCAM-Positive Fetal Liver Cells by Targeting C/EBP?

microRNAs (miRNAs) are short noncoding RNAs that negatively regulate gene expression. Although recent evidences have been indicated that their aberrant expression may play an important role in cancer stem cells, the mechanism of their deregulation in neoplastic transformation of liver cancer stem cells (LCSCs) has not been explored. In our study, the HCC model was established in F344 rats by DEN induction. The EpCAM⁺ cells were sorted out from unfractionated fetal liver cells and liver cancer cells using the FACS analysis and miRNA expression profiles of two groups were screened through microarray platform. Gain-of-function studies were performed in vitro and in vivo to determine the role of miR-92b on proliferation and differentiation of the hepatic progenitors. In addition, luciferase reporter system and gene function analysis were used to predict miR-92b target. we found that miR-92b was highly downregulated in EpCAM⁺ fetal liver cells in expression profiling studies. RT-PCR analysis demonstrated reverse correlation between miR-92b expression and differentiation degree in human HCC samples. Overexpression of miR-92b in EpCAM⁺ fetal liver cells significantly increased proliferation and inhibited differentiation as well as in vitro and in vivo studies. Moreover, we verified that C/EBPß is a direct target of miR-92b and contributes to its effects on proliferation and differentiation. We conclude that aberrant expression of miR-92b can result in proliferation increase and differentiation arrest of hepatic progenitors by targeting C/EBPß.     

生物群落多样性的测度方法Ⅵ:与多样性测度有关的统计问题

物种多样性测度是(群落的)总体参数,它们常常是未知的,需要通过抽样将它们估计出来,因此,必须了解估计量的抽样性质.本文对与一些多样性测度的均值、方差的估计和假设检验以及大、小样本分布等有关的问题作了综述.可以看出大多数多样性测度的抽样性质还不清楚,有些甚至根本就没有研究过.Pielou的合并样方法和刀切法是两个比较通用的方法,用它们可以解决其中的一些问题.但相比之下,刀切法更实用.     

Structural Insights into the Substrate Specificity of a 6-Phospho-β-glucosidase BglA-2 from Streptococcus pneumoniae TIGR4

The 6-phospho-β-glucosidase BglA-2 (EC 3.2.1.86) from glycoside hydrolase family 1 (GH-1) catalyzes the hydrolysis of β-1,4-linked cellobiose 6-phosphate (cellobiose-6′P) to yield glucose and glucose 6-phosphate. Both reaction products are further metabolized by the energy-generating glycolytic pathway. Here, we present the first crystal structures of the apo and complex forms of BglA-2 with thiocellobiose-6′P (a non-metabolizable analog of cellobiose-6′P) at 2.0 and 2.4 Å resolution, respectively. Similar to other GH-1 enzymes, the overall structure of BglA-2 from Streptococcus pneumoniae adopts a typical (β/α)₈ TIM-barrel, with the active site located at the center of the convex surface of the β-barrel. Structural analyses, in combination with enzymatic data obtained from site-directed mutant proteins, suggest that three aromatic residues, Tyr¹²⁶, Tyr³⁰³, and Trp³³⁸, at subsite +1 of BglA-2 determine substrate specificity with respect to 1,4-linked 6-phospho-β-glucosides. Moreover, three additional residues, Ser⁴²⁴, Lys⁴³⁰, and Tyr⁴³² of BglA-2, were found to play important roles in the hydrolytic selectivity toward phosphorylated rather than non-phosphorylated compounds. Comparative structural analysis suggests that a tryptophan versus a methionine/alanine residue at subsite −1 may contribute to the catalytic and substrate selectivity with respect to structurally similar 6-phospho-β-galactosidases and 6-phospho-β-glucosidases assigned to the GH-1 family.     

结核分枝杆菌HspX蛋白的原核高效可溶性表达及产物抗原性分析

目的:利用原核系统可溶性表达结核分枝杆菌HspX蛋白并进行纯化,通过免疫印迹反应初步鉴定重组蛋白的抗原性和特异性。方法:采用PCR方法,从结核分枝杆菌H37Rv基因组中扩增HspX核酸序列,克隆至原核表达载体pET-28a中,转入大肠杆菌BL21(DE3)进行诱导、表达和纯化,用Western印迹初步评价HspX的抗原性。结果:经IPTG诱导,HspX蛋白在原核系统内获得了可溶性表达,经镍柱亲和层析获得了纯度达95%以上的重组蛋白。Western印迹结果证明重组HspX蛋白与结核病患者血清标本呈强阳性反应,与健康人血清标本呈阴性反应。结论:重组蛋白HspX在大肠杆菌中以可溶性形式表达,高纯度的重组融合蛋白有可能成为结核病的血清学诊断抗原。     

Structural and enzymatic characterization of the streptococcal ATP/diadenosine polyphosphate and phosphodiester hydrolase Spr1479/SapH

Spr1479 from Streptococcus pneumoniae R6 is a 33-kDa hypothetical protein of unknown function. Here, we determined the crystal structures of its apo-form at 1.90 Å and complex forms with inorganic phosphate and AMP at 2.30 and 2.20 Å, respectively. The core structure of Spr1479 adopts a four-layer αββα-sandwich fold, with Fe³⁺ and Mn²⁺ coordinated at the binuclear center of the active site (similar to metallophosphoesterases). Enzymatic assays showed that, in addition to phosphodiesterase activity for bis(p-nitrophenyl) phosphate, Spr1479 has hydrolase activity for diadenosine polyphosphate (Ap_nA) and ATP. Residues that coordinate with the two metals are indispensable for both activities. By contrast, the streptococcus-specific residue Trp-67, which binds to phosphate in the two complex structures, is indispensable for the ATP/Ap_nA hydrolase activity only. Moreover, the AMP-binding pocket is conserved exclusively in all streptococci. Therefore, we named the protein SapH for streptococcal ATP/Ap_nA and phosphodiester hydrolase.     

Structural Insights into SraP-Mediated Staphylococcus aureus Adhesion to Host Cells

Staphylococcus aureus, a Gram-positive bacterium causes a number of devastating human diseases, such as infective endocarditis, osteomyelitis, septic arthritis and sepsis. S. aureus SraP, a surface-exposed serine-rich repeat glycoprotein (SRRP), is required for the pathogenesis of human infective endocarditis via its ligand-binding region (BR) adhering to human platelets. It remains unclear how SraP interacts with human host. Here we report the 2.05 Å crystal structure of the BR of SraP, revealing an extended rod-like architecture of four discrete modules. The N-terminal legume lectin-like module specifically binds to N-acetylneuraminic acid. The second module adopts a β-grasp fold similar to Ig-binding proteins, whereas the last two tandem repetitive modules resemble eukaryotic cadherins but differ in calcium coordination pattern. Under the conditions tested, small-angle X-ray scattering and molecular dynamic simulation indicated that the three C-terminal modules function as a relatively rigid stem to extend the N-terminal lectin module outwards. Structure-guided mutagenesis analyses, in addition to a recently identified trisaccharide ligand of SraP, enabled us to elucidate that SraP binding to sialylated receptors promotes S. aureus adhesion to and invasion into host epithelial cells. Our findings have thus provided novel structural and functional insights into the SraP-mediated host-pathogen interaction of S. aureus.     

两科八属十二种(甲壳纲,十足目)淡水蟹触角形态特征的初步观察及在分类研究中的意义

通过体视学显微镜对淡水蟹类2科8属12种的触角结构进行形态学观察,发现淡水蟹类2科8属间触角的形态结构存在可用于形态学分类的特征性结构,其中第1触角比第2触角具有更多的特征性结构,且同种雌雄之间触角形态结构无显著性差异。结果表明,淡水蟹触角的形态结构特征可作为淡水蟹类属间鉴别的形态指标,可作为现有淡水蟹类形态分类系统的补充。