3BP2中SH2结构域的晶体结构及其与来源于FRS2α的肽的复合物晶体结构研究

提出了一个3BP2的Src同源区2结构域(SH2)不同于其他SH2结构域的全新肽链结合模式,它与FRS2来源的多肽结合于不同的氨基酸残基. 实际上,该SH2结构域与该短肽的三个重要残基相结合形成完美的几何互补,通过BioCore实验验证,这三个氨基酸最好是Y-E-N.     

3BP2中SH2结构域的晶体结构及其与来源于FRS2α的肽的复合物

提出了一个3BP2的Src同源区2结构域(SH2)不同于其他SH2结构域的全新肽链结合模式,它与FRS2来源的多肽结合于不同的氨基酸残基. 实际上,该SH2结构域与该短肽的三个重要残基相结合形成完美的几何互补,通过BioCore实验验证,这三个氨基酸最好是Y-E-N.     

类锗烯H_2GeLiCl与RH(R=Cl,SH,PH_2)的插入反应

应用DFT B3LYP和QCISD方法研究类锗烯H2GeLiCl与RH(R=Cl,SH,PH2)的插入反应.在B3LYP/6-311+G(d,p)水平上优化反应势能面上所有驻点的构型,并用QCISD/6-311++G(d,p)方法计算单点能,并考察溶剂化效应对反应的影响.结果表明,类锗烯H2GeLiCl与RH(R=Cl,SH,PH2)插入反应势能面上存在1个过渡态(TS)和1个中间体(IM)连接反应物和产物.气相条件下,3个插入反应的势垒分别为93.47(R=Cl),133.32(R=SH)和212.25(R=PH2)kJ/mol,表明相同条件下发生插入反应时,反应活性由大到小的物质为H-Cl,H-SH,H-PH2;溶剂极性越大,插入反应越容易进行.     

PDLIM2的PDZ结构域晶体结构及其与2-吗啉乙磺酸的相互作用研究

在之前的研究中曾发现PDLIM2 蛋白能够通过其N 端的PDZ 结构域,与H5N1 亚型流感病毒NS1 蛋白的ESEV 序列相互作用. 解析了分辨率0.173 nm 的PDLIM2 的PDZ 结构域晶体结构,发现2-吗啉乙磺酸(MES)分子能够与该PDZ 结构域结合,并且占据PDZ 结构域中与流感病毒NS1 的ESEV 序列相互作用的位点.进一步利用体外GST-pulldown 实验证明,MES 对于NS1 与PDLIM2 之间的相互作用具有一定的抑制效果. 这一发现可能为开发与抗流感病毒相关的药物提供线索.     

c-Src结构域真核表达载体的构建及鉴定

通过聚合酶链式反应(PCR),将c-Src的三个结构域SH3、SH2和KD分别定向克隆至C端带有HA蛋白标签序列的真核表达载体pcDNA3中.经HindIII和XbaI双酶切分析和测序鉴定正确后,应用脂质体法转染HeLa细胞48 h,蛋白免疫印迹法可以检测到细胞内SH3、SH2和KD的表达,证明重组表达质粒pcDNA3-SH2、pcDNA3-SH3和pcDNA3-KD构建成功,为进一步研究Src激酶在肿瘤发生发展中的作用奠定了基础.     

SH2域与磷酸化多肽相互作用的连续溶剂模型研究

使用连续溶剂模型方法研究了SH2结构域与磷酸化多肽pYXXX(X为20种常见氨基酸残基中的任意一种)之间的相互作用.首先计算了已知的SH2域-磷酸化酪氨酸多肽复合物之间的结合能,理论计算的结果与实验测得的亲合能之间的相关系数为0.91,验证了理论模型的正确性.然后,用该模型方法计算了SH2域与pYXXX之间的结合能,分析了磷酸化酪氨酸多肽pYXXX中 1, 2, 3位置上残基对结合能的影响.结果表明 2, 3位置上残基的变化对结合能影响较大, 2位置上带负电的残基和 3位置上的疏水性残基有利于SH2域与pYXXX之间的相互作用,这与实验结果一致.     

生长因子受体介导的信号转导通路研究进展

生长因子受体本身具有酪氨酸激酶活性,它与生长因子结合后发生自动磷酸化并通过酪氨酸磷酸化识别机制作用于含SH2结构域蛋白,启动STATs、Ras、磷脂酶C-γ、磷脂酰肌醇3-激酶、Src激酶等多条胞内信号转导通路.这些通路间的信息交谈和引起基因表达效应的重叠性使它们形成复杂的信号网络系统.     

关于2色P_4问题的一些新的结果

设p(n)是满足下列条件的最小正整数:对于任意大于或等于p(n)的正整数m,在n个顶点的完全图中有一个m边着色,使得其中的任一条长为4的路P4至少含2种颜色.通过对n个顶点的完全图构造新的边着色,得到了2色P4问题的新的上界:2n-3[log3 n]-12(n大于8), 并且对于大于或等于2的正整数k,给出了p(3k-2)与p(3k-1)以及p(3k)的值为3k-12;p(3k+1)的值为3k+12;p(3k+2)的值为3k+32.所得到的结果推广和改进了近期的相关结果.     

[Mn（H2O）6]H2EDTA的合成和晶体结构

合成了一个新配合物[Mn(H2O)6]H2EDTA(MnC10H26N2O14,H4EDTA=乙二胺四乙酸),用单晶X射线衍射法测定了它的晶体结构.晶体属于单斜晶系,空间群P21/c,a=0.78248(2)nm,b=1.3537(3)nm,c=0.84009(2)nm,β=92 18(3)°,V=0.8892(3)nm3,μ=0 820mm-1,Z=2,Mr=453 27,Dc=1 693g/cm3,F(000)=474,R=0 0304,Rw=0 0732.该分子结构为单核单元,Mn原子位于六个水分子构成的八面体场中,Mn(H2O)62+和H2EDTA2-离子间通过氢键构成三维网状结构.     

水合2-苯甲酰基苯甲酸的合成及其晶体结构

水合2-苯甲酰基苯甲酸的晶体结构中一个不对称单元包含1分子2-苯甲酰基苯甲酸和1分子水,分子式为C14H10O3(H2O).具体测定结果如下该晶体属于三斜晶系,P-1空间群,a=0.775 1(2) nm,b=0.837 7(2) nm,c=1.003 7(2) nm,α=75.57(3)°,β=83.05(3)°,γ=86.08(3)°,Dc=1.296 g/cm3,Z=2,F(000)=256,μ=0.095 mm-1,最终偏差因子分别为R=0.054 5,wR=0.146 0.X-射线衍射分析表明,分子之间通过相邻分子间形成的O-H...O氢键相连.水分子中的氧原子由于分子间的氢键作用,稳定性增加.     

Optimization of specificity in a cellular protein interaction network by negative selection

Most proteins that participate in cellular signalling networks contain modular protein-interaction domains. Multiple versions of such domains are present within a given organism: the yeast proteome, for example, contains 27 different Src homology 3 (SH3) domains. This raises the potential problem of cross-reaction. It is generally thought that isolated domain-ligand pairs lack sufficient information to encode biologically unique interactions, and that specificity is instead encoded by the context in which the interaction pairs are presented. Here we show that an isolated peptide ligand from the yeast protein Pbs2 recognizes its biological partner, the SH3 domain from Sho1, with near-absolute specificity--no other SH3 domain present in the yeast genome cross-reacts with the Pbs2 peptide, in vivo or in vitro. Such high specificity, however, is not observed in a set of non-yeast SH3 domains, and Pbs2 motif variants that cross-react with other SH3 domains confer a fitness defect, indicating that the Pbs2 motif might have been optimized to minimize interaction with competing domains specifically found in yeast. System-wide negative selection is a subtle but powerful evolutionary mechanism to optimize specificity within an interaction network composed of overlapping recognition elements.     

Methylated lysine 79 of histone H3 targets 53BP1 to DNA double-strand breaks

The mechanisms by which eukaryotic cells sense DNA double-strand breaks (DSBs) in order to initiate checkpoint responses are poorly understood. 53BP1 is a conserved checkpoint protein with properties of a DNA DSB sensor. Here, we solved the structure of the domain of 53BP1 that recruits it to sites of DSBs. This domain consists of two tandem tudor folds with a deep pocket at their interface formed by residues conserved in the budding yeast Rad9 and fission yeast Rhp9/Crb2 orthologues. In vitro, the 53BP1 tandem tudor domain bound histone H3 methylated on Lys 79 using residues that form the walls of the pocket; these residues were also required for recruitment of 53BP1 to DSBs. Suppression of DOT1L, the enzyme that methylates Lys 79 of histone H3, also inhibited recruitment of 53BP1 to DSBs. Because methylation of histone H3 Lys 79 was unaltered in response to DNA damage, we propose that 53BP1 senses DSBs indirectly through changes in higher-order chromatin structure that expose the 53BP1 binding site.     

Structure of the amino-terminal domain of Cbl complexed to its binding site on ZAP-70 kinase

Cbl is an adaptor protein that functions as a negative regulator of many signalling pathways that start from receptors at the cell surface. The evolutionarily conserved amino-terminal region of Cbl (Cbl-N) binds to phosphorylated tyrosine residues and has cell-transforming activity. Point mutations in Cbl that disrupt its recognition of phosphotyrosine also interfere with its negative regulatory function and, in the case of v-cbl, with its oncogenic potential. In T cells, Cbl-N binds to the tyrosine-phosphorylated inhibitory site of the protein tyrosine kinase ZAP-70. Here we describe the crystal structure of Cbl-N, both alone and in complex with a phosphopeptide that represents its binding site in ZAP-70. The structures show that Cbl-N is composed of three interacting domains: a four-helix bundle (4H), an EF-hand calcium-binding domain, and a divergent SH2 domain that was not recognizable from the amino-acid sequence of the protein. The calcium-bound EF hand wedges between the 4H and SH2 domains and roughly determines their relative orientation. In the ligand-occupied structure, the 4H domain packs against the SH2 domain and completes its phosphotyrosine-recognition pocket. Disruption of this binding to ZAP-70 as a result of structure-based mutations in the 4H, EF-hand and SH2 domains confirms that the three domains together form an integrated phosphoprotein-recognition module.     

多肽序列优化降低c-Src蛋白靶向药物的毒性风险

避免c-Src蛋白的多肽类拮抗剂与多个蛋白发生混杂性结合,对于降低抗癌药物的毒性风险具有重要作用。本研究运用生物信息学方法对氨基酸序列进行优化设计,旨在减少混杂性结合的发生。本研究综合利用各种多肽数据库和生物信息学工具,首先总结了多肽分子与多个蛋白SH3结构域之间潜在的混杂性结合,并发现了其中的内在规律。随后,根据所发现的规律,对多肽的氨基酸序列进行针对性的优化设计。结果表明,大多数多肽在经过优化后,所结合的c-Src以外的蛋白数量都有所下降,从而显著提高了多肽与c-Src蛋白之间结合的特异性(P0.05),并降低了其潜在的毒性风险。本研究所取得的结果将为设计具有高度特异性和低毒性的靶向性多肽药物提供参考。     

Structural basis of the alpha1-beta subunit interaction of voltage-gated Ca2+ channels

High-voltage-activated Ca2+ channels are essential for diverse biological processes. They are composed of four or five subunits, including alpha1, alpha2-delta, beta and gamma (ref. 1). Their expression and function are critically dependent on the beta-subunit, which transports alpha1 to the surface membrane and regulates diverse channel properties. It is believed that the beta-subunit interacts with alpha1 primarily through the beta-interaction domain (BID), which binds directly to the alpha-interaction domain (AID) of alpha1; however, the molecular mechanism of the alpha1-beta interaction is largely unclear. Here we report the crystal structures of the conserved core region of beta3, alone and in complex with AID, and of beta4 alone. The structures show that the beta-subunit core contains two interacting domains: a Src homology 3 (SH3) domain and a guanylate kinase (GK) domain. The AID binds to a hydrophobic groove in the GK domain through extensive interactions, conferring extremely high affinity between alpha1 and beta-subunits. The BID is essential both for the structural integrity of and for bridging the SH3 and GK domains, but it does not participate directly in binding alpha1. The presence of multiple protein-interacting modules in the beta-subunit opens a new dimension to its function as a multi-functional protein.     

Structure of an SH2 domain of the p85 alpha subunit of phosphatidylinositol-3-OH kinase.

Receptor protein-tyrosine kinases, through phosphorylation of specific tyrosine residues, generate high-affinity binding sites which direct assembly of multienzyme signalling complexes. Many of these signalling proteins, including phospholipase C gamma, GTPase-activating protein and phosphatidylinositol-3-OH kinase, contain src-homology 2 (SH2) domains, which bind with high affinity and specificity to tyrosine-phosphorylated sequences. The critical role played by SH2 domains in signalling has been highlighted by recent studies showing that mutation of specific phosphorylation sites on the platelet-derived growth factor receptor impair its association with phosphatidylinositol-3-OH kinase, preventing growth factor-induced mitogenesis. Here we report the solution structure of an isolated SH2 domain from the 85K regulatory subunit of phosphatidylinositol-3-OH kinase, determined using multidimensional nuclear magnetic resonance spectroscopy. The structure is characterized by a central region of beta-sheet flanked by two alpha-helices, with a highly flexible loop close to functionally important residues previously identified by site-directed mutagenesis.     

Phospholipid binding by a synaptic vesicle protein homologous to the regulatory region of protein kinase C

Neurotransmitters are released at synapses by the Ca2(+)-regulated exocytosis of synaptic vesicles, which are specialized secretory organelles that store high concentrations of neurotransmitters. The rapid Ca2(+)-triggered fusion of synaptic vesicles is presumably mediated by specific proteins that must interact with Ca2+ and the phospholipid bilayer. We now report that the cytoplasmic domain of p65, a synaptic vesicle-specific protein that binds calmodulin contains an internally repeated sequence that is homologous to the regulatory C2-region of protein kinase C (PKC). The cytoplasmic domain of recombinant p65 binds acidic phospholipids with a specificity indicating an interaction of p65 with the hydrophobic core as well as the headgroups of the phospholipids. The binding specificity resembles PKC, except that p65 also binds calmodulin, placing the C2-regions in a context of potential Ca2(+)-regulation that is different from PKC. This is a novel homology between a cellular protein and the regulatory domain of protein kinase C. The structure and properties of p65 suggest that it may have a role in mediating membrane interactions during synaptic vesicle exocytosis.     

Structural mechanism of WASP activation by the enterohaemorrhagic E. coli effector EspF(U)

During infection, enterohaemorrhagic Escherichia coli (EHEC) takes over the actin cytoskeleton of eukaryotic cells by injecting the EspF(U) protein into the host cytoplasm. EspF(U) controls actin by activating members of the Wiskott-Aldrich syndrome protein (WASP) family. Here we show that EspF(U) binds to the autoinhibitory GTPase binding domain (GBD) in WASP proteins and displaces it from the activity-bearing VCA domain (for verprolin homology, central hydrophobic and acidic regions). This interaction potently activates WASP and neural (N)-WASP in vitro and induces localized actin assembly in cells. In the solution structure of the GBD-EspF(U) complex, EspF(U) forms an amphipathic helix that binds the GBD, mimicking interactions of the VCA domain in autoinhibited WASP. Thus, EspF(U) activates WASP by competing directly for the VCA binding site on the GBD. This mechanism is distinct from that used by the eukaryotic activators Cdc42 and SH2 domains, which globally destabilize the GBD fold to release the VCA. Such diversity of mechanism in WASP proteins is distinct from other multimodular systems, and may result from the intrinsically unstructured nature of the isolated GBD and VCA elements. The structural incompatibility of the GBD complexes with EspF(U) and Cdc42/SH2, plus high-affinity EspF(U) binding, enable EHEC to hijack the eukaryotic cytoskeletal machinery effectively.