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1.
Hoffmann R 《Science (New York, N.Y.)》1981,211(4486):995-1002
Organometallic chemists have synthesized a remarkable variety of new structural types. In these structures ligands, which are organic or inorganic molecules of variable independent stability, bind to one or more transition metal atoms. An approach to an understanding of the electronic structure, geometrical preferences, and reactivity of these complexes may be made if the molecule is "decomposed" conceptually into a metal fragment, ML(n), and a ligand. A library of the molecular orbitals of these fragments is becoming available. One then "reconstructs" the molecule by examining the interaction of the orbitals of the ligand, typically an organic molecule, with the orbitals of the ML(n), fragment. 相似文献
2.
Xiong JP Stehle T Zhang R Joachimiak A Frech M Goodman SL Arnaout MA 《Science (New York, N.Y.)》2002,296(5565):151-155
The structural basis for the divalent cation-dependent binding of heterodimeric alphabeta integrins to their ligands, which contain the prototypical Arg-Gly-Asp sequence, is unknown. Interaction with ligands triggers tertiary and quaternary structural rearrangements in integrins that are needed for cell signaling. Here we report the crystal structure of the extracellular segment of integrin alphaVbeta3 in complex with a cyclic peptide presenting the Arg-Gly-Asp sequence. The ligand binds at the major interface between the alphaV and beta3 subunits and makes extensive contacts with both. Both tertiary and quaternary changes are observed in the presence of ligand. The tertiary rearrangements take place in betaA, the ligand-binding domain of beta3; in the complex, betaA acquires two cations, one of which contacts the ligand Asp directly and the other stabilizes the ligand-binding surface. Ligand binding induces small changes in the orientation of alphaV relative to beta3. 相似文献
3.
Nucleic acid molecules play crucial roles in diverse biological processes including the storage, transport, processing, and expression of the genetic information. Nucleic acid aptamers are selected in vitro from libraries containing random sequences of up to a few hundred nucleotides. Selection is based on the ability to bind ligand molecules with high affinity and specificity. Three-dimensional structures have been determined at high resolution for a number of aptamers in complex with their cognate ligands. Structures of aptamer complexes reveal the key molecular interactions conferring specificity to the aptamer-ligand association, including the precise stacking of flat moieties, specific hydrogen bonding, and molecular shape complementarity. These basic principles of discriminatory molecular interactions in aptamer complexes parallel recognition events central to many cellular processes involving nucleic acids. 相似文献
4.
【目的】比较荧光竞争结合试验(fluorescence competitive binding assay)和微量热涌动(microscale thermophoresis,MST)技术在研究绿盲蝽(Apolygus lucorum)气味结合蛋白(odorant binding proteins,OBPs)Aluc OBP21配体结合特性上的差异,探索一种新的测定昆虫OBPs结合功能的方法。【方法】提取绿盲蝽雌、雄成虫触角总RNA并进行反转录,获得绿盲蝽成虫触角c DNA。采用特异性克隆引物,以绿盲蝽成虫触角c DNA为模板进行PCR扩增,构建p ET32a/Aluc OBP21重组质粒。将重组质粒转化至BL21(DE3)感受态细胞进行原核表达,获得含表达标签的重组Aluc OBP21蛋白。通过高亲和Ni-NTA纯化介质对重组粗蛋白进行纯化,采用重组肠激酶切掉His-tag标签,最终获得无表达标签的重组Aluc OBP21蛋白。利用荧光竞争结合试验,以1-N-phenylnaphthylamine(1-NPN)为荧光探针研究重组Aluc OBP21蛋白与候选配体的结合特性,其中1-NPN和气味标样均溶解在质谱纯级的甲醇中。同时,利用MST技术解析重组Aluc OBP21蛋白与候选配体的结合特性,候选配体标样溶解在二甲基亚砜(dimethyl sulfoxide,DMSO)溶液中。候选配体化合物包括8种潜在的盲蝽性信息素及性信息素类似物、12种植物绿叶挥发物和绿盲蝽驱避剂主要组分二甲基二硫醚等。【结果】重组Aluc OBP21蛋白在上清液和包涵体均能够表达,最终选择上清组分进行目标蛋白纯化,利用重组肠激酶在22℃切除His-tag标签得到无标签的重组Aluc OBP21蛋白。荧光竞争结合试验结果显示,重组Aluc OBP21与荧光探针1-NPN的解离常数为(6.88±0.31)μmol·L~(-1),Aluc OBP21能够与β-紫罗兰酮和β-石竹烯结合,解离常数分别为(13.74±1.93)和(13.24±2.12)μmol·L~(-1),而其他候选配体均不能与重组Aluc OBP21有效结合。MST测试结果显示,Aluc OBP21可以与β-石竹烯、β-紫罗兰酮、β-蒎烯和柠檬烯有效结合,解离常数分别为(0.20±0.02)、(0.05±0.01)、(0.70±0.04)和(0.40±0.06)μmol·L~(-1)。其余候选配体化合物与Aluc OBP21的热涌动不能随配体浓度变化而表现有规律的变化,故这些气味化合物不能与Aluc OBP21发生结合作用。【结论】MST检测与荧光竞争结合试验相比,MST所得配体结合谱更广,不会遗漏一些结合力较弱的气味配体。 相似文献
5.
Extracellular ligand binding to G protein-coupled receptors (GPCRs) modulates G protein and β-arrestin signaling by changing the conformational states of the cytoplasmic region of the receptor. Using site-specific (19)F-NMR (fluorine-19 nuclear magnetic resonance) labels in the β(2)-adrenergic receptor (β(2)AR) in complexes with various ligands, we observed that the cytoplasmic ends of helices VI and VII adopt two major conformational states. Changes in the NMR signals reveal that agonist binding primarily shifts the equilibrium toward the G protein-specific active state of helix VI. In contrast, β-arrestin-biased ligands predominantly impact the conformational states of helix VII. The selective effects of different ligands on the conformational equilibria involving helices VI and VII provide insights into the long-range structural plasticity of β(2)AR in partial and biased agonist signaling. 相似文献
6.
Three-dimensional structure of favin: saccharide binding-cyclic permutation in leguminous lectins 总被引：4，自引：0，他引：4
The three-dimensional structure of favin, the glucose- and mannose-binding lectin of Vicia faba (vetch, broad bean), has been determined at a resolution of 2.8 angstroms by molecular replacement. The crystals contain specifically bound glucose and provide the first high-resolution view of specific saccharide binding in a leguminous lectin. The structure is similar to those of concanavalin A (Con A) and green pea lectin; differences from Con A show that minimal changes are needed to accommodate the cyclic permutation in amino acid sequence between the two molecules. The molecule is an ellipsoidal dimer dominated by extensive beta structures. Each protomer contains binding sites for two divalent metal ions (Mn2+ and Ca2+) and a specific saccharide. Glucose is bound by favin in a cleft in the molecular surface and has noncovalent contacts primarily with two peptide loops, one of which contains several metal ion ligands. The specific carbohydrate-binding site is similar to that of Con A in location and general peptide folding, despite several differences in specific amino acid residues. 相似文献
7.
The existence of synthetic macrocyclic molecules with hydrophilic cavities containing multiple binding atoms and with hydrophobic exteriors gives rise to extraordinary possibilities with respect to the design and synthesis of molecules with specific cation and anion binding properties. The preparation of many new macrocyclic compounds has recently been reported, but few practical applications for them have been suggested. From the information available, it is becoming clear that it should be possible to synthesize macrocycles that will have specified, or selected, ion binding properties. Cavity size can be varied to accommodate only those cations or anions within a specified narrow band of sizes. Numbers and types of coordinating atoms can be chosen to give essentially electrostatic or covalent bonding or a combination of the two in a metalmacrocycle complex. The metal ligand bond appears to be predominantly ionic in the case of the cyclic polyethers but the covalent character increases on substitution of sulfur or nitrogen for oxygen donor atoms. The essential hydrophobic exteriors of the macrocycles can be modified by the addition of side chains and groups to facilitate the solution of anions and cations in organic solvents. The structures of many macrocycles can be made to approximate naturally occurring molecules, that is, cyclic polyethers similar to macrocyclic antibiotics of the valinomycin and nonactin types and cyclic polyamines similar to porphyrins. Macrocycles are also useful as model compounds for the study of metal interactions with biological systems. The synthetic macrocycles thus represent an intriguing new area of coordination chemistry, the systematic study of which should lead to many interesting and useful chemical applications in the field of metal complexation in solution. 相似文献
8.
在昆虫触角中,位于嗅觉感器神经树突膜上的气味受体蛋白与同源配位体相互作用将化学信号转换为神经活动.在与气味受体相互作用前,这些疏水性的配位体必须进入和穿过含有高度聚集气味降解酶的水环境,气味分子和气味结合蛋白OBP相互作用,在水腔和感器的表皮毛壁的交界面上与气味分子结合,通过扩散穿过水腔,将气味运送到神经细胞膜受体.接收后传入中枢神经系统.中枢神经系统对所有感官器官接收信号进行整合,最后使效应器官产生行为反应.对昆虫感受气味物质的分子机制进行了探讨. 相似文献
9.
为了以量子点为探针建立简便快速的病原微生物检测方法,采用配体交换法将具有微生物特异性的糖链偶联到CdSeS/ZnS量子点表面,制备2种糖量子点复合材料（甘露糖-量子点和半乳糖-量子点）。通过对它们的结构、物性和光谱学特性进行表征,结果显示：2种糖量子点均具有良好的水溶性、荧光发射和紫外-可见光吸收性能。进一步以这2种糖... 相似文献
10.
Systematic evolution of ligands by exponential enrichment: RNA ligands to bacteriophage T4 DNA polymerase 总被引：248，自引：0，他引：248
High-affinity nucleic acid ligands for a protein were isolated by a procedure that depends on alternate cycles of ligand selection from pools of variant sequences and amplification of the bound species. Multiple rounds exponentially enrich the population for the highest affinity species that can be clonally isolated and characterized. In particular one eight-base region of an RNA that interacts with the T4 DNA polymerase was chosen and randomized. Two different sequences were selected by this procedure from the calculated pool of 65,536 species. One is the wild-type sequence found in the bacteriophage mRNA; one is varied from wild type at four positions. The binding constants of these two RNA's to T4 DNA polymerase are equivalent. These protocols with minimal modification can yield high-affinity ligands for any protein that binds nucleic acids as part of its function; high-affinity ligands could conceivably be developed for any target molecule. 相似文献
11.
Mutations introduced into human growth hormone (hGH) (Thr175 --> Gly-hGH) and the extracellular domain of the hGH receptor (Trp104 --> Gly-hGHbp) created a cavity at the protein-protein interface that resulted in binding affinity being reduced by a factor of 10(6). A small library of indole analogs was screened for small molecules that bind the cavity created by the mutations and restore binding affinity. The ligand 5-chloro-2-trichloromethylimidazole was found to increase the affinity of the mutant hormone for its receptor more than 1000-fold. Cell proliferation and JAK2 phosphorylation assays showed that the mutant hGH activates growth hormone signaling in the presence of added ligand. This approach may allow other protein-protein and protein-nucleic acid interactions to be switched on or off by the addition or depletion of exogenous small molecules. 相似文献
12.
Structural heterogeneity and functional domains of murine immunoglobulin G Fc receptors 总被引：54，自引：0，他引：54
J V Ravetch A D Luster R Weinshank J Kochan A Pavlovec D A Portnoy J Hulmes Y C Pan J C Unkeless 《Science (New York, N.Y.)》1986,234(4777):718-725
Binding of antibodies to effector cells by way of receptors to their constant regions (Fc receptors) is central to the pathway that leads to clearance of antigens by the immune system. The structure and function of this important class of receptors on immune cells is addressed through the molecular characterization of Fc receptors (FcR) specific for the murine immunoglobulin G isotype. Structural diversity is encoded by two genes that by alternative splicing result in expression of molecules with highly conserved extracellular domains and different transmembrane and intracytoplasmic domains. The proteins encoded by these genes are members of the immunoglobulin supergene family, most homologous to the major histocompatibility complex molecule E beta. Functional reconstitution of ligand binding by transfection of individual FcR genes demonstrates that the requirements for ligand binding are encoded in a single gene. These studies demonstrate the molecular basis for the functional heterogeneity of FcR's, accounting for the possible transduction of different signals in response to a single ligand. 相似文献
13.
翟仁通 《山西农业大学学报(自然科学版)》1983,(1)
自然界特别是在生物体系中广泛地存在着混合型络合物。它的形成可以是一步同时生成或逐步生成,也可以是由单一型络合物混合生成。混合络合物的稳定性是由如下因素所决定的,即:统计效应,静电效应,共价键性,立体效应和配体的合作效应。在生物体内,混合络合物的形成涉及到:生物分子的稳定化和三维构象的稳定化,金属离子和配体分子的分布和运转,某些金属酶的催化作用(如脱羧酶、水解酶,羰基水化酶,碳酸酐酶等)及生物固氮等等问题。 相似文献
14.
Molecular and in vitro biochemical assessment of chemosensory protein 10 from brown planthopper Nilaparvata lugens at acidic pH 
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下载免费PDF全文 Muhammad Irfan WARIS Aneela YOUNAS Rana Muhammad Kaleem ULLAH Fatima RASOOL Muhammad Muzammal ADEEL WANG Man-qun 《农业科学学报》2022,21(3):781-796
Chemosensory proteins (CSPs) are important molecular components of the insect olfactory system, which are involved in capturing, binding, and transporting hydrophobic odour molecules across the sensillum in sensillar lymph in regulating insect behavior. This protein family (CSPs) is also involved in many other systems that are not linked to olfactory receptors in olfactory sensilla. The brown planthopper (BPH) is a monophagous pest of rice that causes damage by sucking phloem sap and transmitting a number of diseases caused by viruses. In this study, fluorescence competitive binding assay and fluorescence quenching assay at acidic pH were performed as well as homology modelling to describe the binding affinity of NlugCSP10. Fluorescence competitive binding assay (FCBA) demonstrated that NlugCSP10 bound strongly to nonadecane, farnesene, and 2-tridecanone at acidic pH. The results of FCBA indicated that NlugCSP10 bound different ligands at the physiological pH (5.0) of the bulk sensillum lymph. Fluorescence quenching assay demonstrated that NlugCSP10 generated a stable complex with 2-tridecanone, while two ligands nonadecane and farnesene collided due to molecular collisions. The interaction of selected ligands with the modelled structure of NlugCSP10 was also analyzed, which found the key amino acids (Gln23, Gln24, Gln25, Asn27, Met33, Ser34, Ile35, Tyr36, Asn42, Met43, Val45, Asn46, Asn93, Arg96, Ala97, Lys99, and Ala100) in NlugCSP10 that were involved in binding of volatile compounds. The present study contributes to the binding profile of NlugCSP10 that promotes the development of behaviorally active ligands based on BPH olfactory system. 相似文献
15.
Seeger MA Schiefner A Eicher T Verrey F Diederichs K Pos KM 《Science (New York, N.Y.)》2006,313(5791):1295-1298
The AcrA/AcrB/TolC complex spans the inner and outer membranes of Escherichia coli and serves as its major drug-resistance pump. Driven by the proton motive force, it mediates the efflux of bile salts, detergents, organic solvents, and many structurally unrelated antibiotics. Here, we report a crystallographic structure of trimeric AcrB determined at 2.9 and 3.0 angstrom resolution in space groups that allow asymmetry of the monomers. This structure reveals three different monomer conformations representing consecutive states in a transport cycle. The structural data imply an alternating access mechanism and a novel peristaltic mode of drug transport by this type of transporter. 相似文献
16.
Crystal structures of human cytochrome P450 3A4 bound to metyrapone and progesterone 总被引：1，自引：0，他引：1
Williams PA Cosme J Vinkovic DM Ward A Angove HC Day PJ Vonrhein C Tickle IJ Jhoti H 《Science (New York, N.Y.)》2004,305(5684):683-686
Cytochromes P450 (P450s) metabolize a wide range of endogenous compounds and xenobiotics, such as pollutants, environmental compounds, and drug molecules. The microsomal, membrane-associated, P450 isoforms CYP3A4, CYP2D6, CYP2C9, CYP2C19, CYP2E1, and CYP1A2 are responsible for the oxidative metabolism of more than 90% of marketed drugs. Cytochrome P450 3A4 (CYP3A4) metabolizes more drug molecules than all other isoforms combined. Here we report three crystal structures of CYP3A4: unliganded, bound to the inhibitor metyrapone, and bound to the substrate progesterone. The structures revealed a surprisingly small active site, with little conformational change associated with the binding of either compound. An unexpected peripheral binding site is identified, located above a phenylalanine cluster, which may be involved in the initial recognition of substrates or allosteric effectors. 相似文献
17.
Regulated cleavage of a contact-mediated axon repellent 总被引：2，自引：0，他引：2
Contact-mediated axon repulsion by ephrins raises an unresolved question: these cell surface ligands form a high-affinity multivalent complex with their receptors present on axons, yet rather than being bound, axons can be rapidly repelled. We show here that ephrin-A2 forms a stable complex with the metalloprotease Kuzbanian, involving interactions outside the cleavage region and the protease domain. Eph receptor binding triggered ephrin-A2 cleavage in a localized reaction specific to the cognate ligand. A cleavage-inhibiting mutation in ephrin-A2 delayed axon withdrawal. These studies reveal mechanisms for protease recognition and control of cell surface proteins, and, for ephrin-A2, they may provide a means for efficient axon detachment and termination of signaling. 相似文献
18.
Crystal structures of an antibody to a peptide and its complex with peptide antigen at 2.8 A 总被引：16，自引：0，他引：16
The three-dimensional structures of an antibody to a peptide and its complex with the peptide antigen have been determined at 2.8 A resolution. The antigen is a synthetic 19-amino acid peptide homolog of the C helix of myohemerythrin (Mhr). The unliganded Fab' crystals are orthorhombic with two molecules per asymmetric unit, whereas the complex crystals are hexagonal with one molecule per asymmetric unit. The Fab' and the Fab'-peptide complex structures have been solved independently by molecular replacement methods and have crystallographic R factors of 0.197 and 0.215, respectively, with no water molecules included. The amino-terminal portion of the peptide sequence (NH2-Glu-Val-Val-Pro-His-Lys-Lys) is clearly interpretable in the electron density map of the Fab'-peptide complex and adopts a well-defined type II beta-turn in the concave antigen binding pocket. This same peptide amino acid sequence in native Mhr is alpha-helical. The peptide conformation when bound to the Fab' is inconsistent with binding of the Fab' to native Mhr, and suggests that binding of the Fab' to conformationally altered forms of the native Mhr or to apo-Mhr. Immunological mapping previously identified this sequence as the peptide epitope, and its fine specificity correlates well with the structural analysis. The binding pocket includes a large percentage of hydrophobic residues. The buried surfaces of the peptide and the antibody are complementary in shape and cover 460 A2 and 540 A2, respectively. These two structures now enable a comparison of a specific monoclonal Fab' both in its free and antigen complexed state. While no major changes in the antibody were observed when peptide was bound, there were some small but significant side chain and main chain rearrangements. 相似文献
19.
Riboswitches are untranslated regions of messenger RNA, which adopt alternate structures depending on the binding of specific metabolites. Such conformational switching regulates the expression of proteins involved in the biosynthesis of riboswitch substrates. Here, we present the 2.9 angstrom-resolution crystal structure of the eukaryotic Arabidopsis thaliana thiamine pyrophosphate (TPP)-specific riboswitch in complex with its natural ligand. The riboswitch specifically recognizes the TPP via conserved residues located within two highly distorted parallel "sensor" helices. The structure provides the basis for understanding the reorganization of the riboswitch fold upon TPP binding and explains the mechanism of resistance to the antibiotic pyrithiamine. 相似文献
20.
A single antibody was shown to adopt different binding-site conformations and thereby bind unrelated antigens. Analysis by both x-ray crystallography and pre-steady-state kinetics revealed an equilibrium between different preexisting isomers, one of which possessed a promiscuous, low-affinity binding site for aromatic ligands, including the immunizing hapten. A subsequent induced-fit isomerization led to high-affinity complexes with a deep and narrow binding site. A protein antigen identified by repertoire selection made use of an unrelated antibody isomer with a wide, shallow binding site. Conformational diversity, whereby one sequence adopts multiple structures and multiple functions, can increase the effective size of the antibody repertoire but may also lead to autoimmunity and allergy. 相似文献