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Letteratura scientifica selezionata sul tema "Receptor-ligand complexes"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 26 luglio 2024

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Articoli di riviste sul tema "Receptor-ligand complexes"

1

Veeramani, Suresh, e George J. Weiner. "Quantification of Receptor Occupancy by Ligand—An Understudied Class of Potential Biomarkers". Cancers 12, n. 10 (13 ottobre 2020): 2956. http://dx.doi.org/10.3390/cancers12102956.

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Molecular complexes, such as ligand–receptor complexes, are vital for both health and disease and can be shed into the circulation in soluble form. Relatively little is known about the biology of soluble ligand–receptor complexes. The functional importance of such complexes and their potential use as clinical biomarkers in diagnosis and therapy remains underappreciated. Most traditional technologies used to study ligand–receptor complexes measure the individual levels of soluble ligands or receptors rather than the complexes themselves. The fraction of receptors occupied by ligand, and the potential clinical relevance of such information, has been largely overlooked. Here, we review the biological significance of soluble ligand–receptor complexes with a specific focus on their potential as biomarkers of cancer and other inflammatory diseases. In addition, we discuss a novel RNA aptamer-based technology, designated ligand–receptor complex-binding aptamers (LIRECAP), that can provide precise measurement of the fraction of a soluble receptor occupied by its ligand. The potential applicability of the LIRECAP technology as a biomarker discovery platform is also described.

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2

Guvench, Olgun, Daniel J. Price e Charles L. Brooks. "Receptor rigidity and ligand mobility in trypsin-ligand complexes". Proteins: Structure, Function, and Bioinformatics 58, n. 2 (1 dicembre 2004): 407–17. http://dx.doi.org/10.1002/prot.20326.

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3

Särndahl, E., M. Lindroth, T. Bengtsson, M. Fällman, J. Gustavsson, O. Stendahl e T. Andersson. "Association of ligand-receptor complexes with actin filaments in human neutrophils: a possible regulatory role for a G-protein." Journal of Cell Biology 109, n. 6 (1 dicembre 1989): 2791–99. http://dx.doi.org/10.1083/jcb.109.6.2791.

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Most ligand-receptor interactions result in an immediate generation of various second messengers and a subsequent association of the ligand-receptor complex to the cytoskeleton. Depending on the receptor involved, this linkage to the cytoskeleton has been suggested to play a role in the termination of second messenger generation and/or the endocytic process whereby the ligand-receptor complex is internalized. We have studied how the binding of chemotactic peptide-receptor complexes to the cytoskeleton of human neutrophils is accomplished. As much as 76% of the tritiated formylmethionyl-leucyl-phenylalanine (fMet-Leu-[3H]Phe) specifically bound to intact cells, obtained by a 30-s stimulation with 20 nM fMet-Leu-[3H]Phe, still remained after Triton X-100 extraction. Preincubating intact cells with dihydrocytochalasin B (dhCB) or washing the cytoskeletal preparation with a high concentration of potassium, reduced the binding of ligand-receptor complexes to the cytoskeleton by 46% or more. Inhibition of fMet-Leu-Phe-induced generation of second messengers by ADP-ribosylating the alpha-subunit of the receptor-coupled G-protein with pertussis toxin, did not reduce the binding of ligand-receptor complexes to the cytoskeleton. However, using guanosine-5'-O-(2-thiodiphosphate) (GDP beta S) to prevent the dissociation of the fMet-Leu-Phe-associated G-protein within electrically permeabilized cells, led to a pronounced reduction (62%) of the binding between ligand-receptor complexes and the cytoskeleton. In summary, in human neutrophils the rapid association between chemotactic peptide-receptor complexes and the cytoskeleton is dependent on filamentous actin. This association is most likely regulated by the activation and dissociation of the fMet-Leu-Phe-associated G-protein.

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4

Suthaus, Jan, Anna Tillmann, Inken Lorenzen, Elena Bulanova, Stefan Rose-John e Jürgen Scheller. "Forced Homo- and Heterodimerization of All gp130-Type Receptor Complexes Leads to Constitutive Ligand-independent Signaling and Cytokine-independent Growth". Molecular Biology of the Cell 21, n. 15 (agosto 2010): 2797–807. http://dx.doi.org/10.1091/mbc.e10-03-0240.

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Naturally ligand independent constitutively active gp130 variants were described to be responsible for inflammatory hepatocellular adenomas. Recently, we genetically engineered a ligand-independent constitutively active gp130 variant based on homodimerization of Jun leucine zippers. Because also heterodimeric complexes within the gp130 family may have tumorigenic potential, we seek to generate ligand-independent constitutively active heterodimers for all known gp130-receptor complexes based on IL-15/IL-15Rα-sushi fusion proteins. Ligand-independent heterodimerization of gp130 with WSX-1, LIFR, and OSMR and of OSMR with GPL led to constitutive, ligand-independent STAT1 and/or STAT3 and ERK1/2 phosphorylation. Moreover, these receptor combinations induced transcription of the STAT3 target genes c-myc and Pim-1 and factor-independent growth of stably transduced Ba/F3-gp130 cells. Here, we establish the IL-15/IL-15Rα-sushi system as a new system to mimic constitutive and ligand-independent activation of homo- and heterodimeric receptor complexes, which might be applicable to other heterodimeric receptor families. A mutated IL-15 protein, which was still able to bind the IL-15Rα-sushi domain, but not to β- and γ-receptor chains, in combination with the 2A peptide technology may be used to translate our in vitro data into the in vivo situation to assess the tumorigenic potential of gp130-heterodimeric receptor complexes.

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5

Czekay, R. P., R. A. Orlando, L. Woodward, M. Lundstrom e M. G. Farquhar. "Endocytic trafficking of megalin/RAP complexes: dissociation of the complexes in late endosomes." Molecular Biology of the Cell 8, n. 3 (marzo 1997): 517–32. http://dx.doi.org/10.1091/mbc.8.3.517.

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Megalin (gp330) is a member of the low-density lipoprotein receptor gene family. Like other members of the family, it is an endocytic receptor that binds a number of specific ligands. Megalin also binds the receptor-associated protein (RAP) that serves as an exocytic traffic chaperone and inhibits ligand binding to the receptor. To investigate the fate of megalin/RAP complexes, we bound RAP glutathione-S-transferase fusion protein (RAP-GST) to megalin at the surface of L2 yolk sac carcinoma cells and followed the trafficking of the complexes by immunofluorescence and immunogold labeling and by their distribution on Percoll gradients. We show that megalin/RAP-GST complexes, which are internalized via clathrin-coated pits, are delivered to early endosomes where they accumulate during an 18 degrees C temperature block and colocalize with transferrin and transferrin receptor. Upon release from the temperature block, the complexes travel to late endosomes where they colocalize with rab7 and can be coprecipitated with anti-RAP-GST antibodies. Dissociation of the complex occurs in late endosomes and is most likely triggered by the low pH (approximately 5.5) of this compartment. RAP is then rapidly delivered to lysosomes and degraded whereas megalin is recycled to the cell surface. When the ligand, lipoprotein lipase, was bound to megalin, the receptor was found to recycle through early endosomes. We conclude that in contrast to receptor/ligand complexes, megalin/RAP complexes traffic through late endosomes, which is a novelty for members of the low-density lipoprotein receptor gene family.

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6

Niu, Linghao, David W. Golde, Juan Carlos Vera e Mark L. Heaney. "Kinetic Resolution of Two Mechanisms for High-Affinity Granulocyte-Macrophage Colony-Stimulating Factor Binding to Its Receptor". Blood 94, n. 11 (1 dicembre 1999): 3748–53. http://dx.doi.org/10.1182/blood.v94.11.3748.423k16_3748_3753.

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Granulocyte-macrophage colony-stimulating factor (GM-CSF) is an important hematopoietic cytokine that exerts its effects by interaction with the GM-CSF receptor (GMR) on the surface of responsive cells. The GM-CSF receptor consists of two subunits: GMR, which binds GM-CSF with low affinity, and GMRβ, which lacks intrinsic ligand-binding capability but complexes with GMR to form a high-affinity receptor (GMR/β). We conducted dynamic kinetic analyses of GM-CSF receptors to define the role of GMRβ in the interaction of ligand and receptor. Our data show that GMR/β exhibits a higher kon than GMR, indicating that GMRβ facilitates ligand acquisition to the binding pocket. Heterogeneity with regard to GM-CSF dissociation from GMR/β points to the presence of loose and tight ligand-receptor complexes in high-affinity binding. Although the loose complex has a koff similar to GMR, the lower koffindicates that GMRβ inhibits GM-CSF release from the tight receptor complex. The two rates of ligand dissociation may provide for discrete mechanisms of interaction between GM-CSF and its high-affinity receptor. These results show that the β subunit functions to stabilize ligand binding as well as to facilitate ligand acquisition.

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7

Clark, Kevin P., e Ajay. "Flexible ligand docking without parameter adjustment across four ligand-receptor complexes". Journal of Computational Chemistry 16, n. 10 (ottobre 1995): 1210–26. http://dx.doi.org/10.1002/jcc.540161004.

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8

Meijsing, Sebastiaan H., Cem Elbi, Hans F. Luecke, Gordon L. Hager e Keith R. Yamamoto. "The Ligand Binding Domain Controls Glucocorticoid Receptor Dynamics Independent of Ligand Release". Molecular and Cellular Biology 27, n. 7 (29 gennaio 2007): 2442–51. http://dx.doi.org/10.1128/mcb.01570-06.

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ABSTRACT Ligand binding to the glucocorticoid receptor (GR) results in receptor binding to glucocorticoid response elements (GREs) and the formation of transcriptional regulatory complexes. Equally important, these complexes are continuously disassembled, with active processes driving GR off GREs. We found that cochaperone p23-dependent disruption of GR-driven transcription depended on the ligand binding domain (LBD). Next, we examined the importance of the LBD and of ligand dissociation in GR-GRE dissociation in living cells. We showed in fluorescence recovery after photobleaching studies that dissociation of GR from GREs is faster in the absence of the LBD. Furthermore, GR interaction with a target promoter revealed ligand-specific exchange rates. However, using covalently binding ligands, we demonstrated that ligand dissociation is not required for receptor dissociation from GREs. Overall, these studies showed that activities impinging on the LBD regulate GR exchange with GREs but that the dissociation of GR from GREs is independent from ligand dissociation.

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9

Niu, Linghao, David W. Golde, Juan Carlos Vera e Mark L. Heaney. "Kinetic Resolution of Two Mechanisms for High-Affinity Granulocyte-Macrophage Colony-Stimulating Factor Binding to Its Receptor". Blood 94, n. 11 (1 dicembre 1999): 3748–53. http://dx.doi.org/10.1182/blood.v94.11.3748.

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Abstract Granulocyte-macrophage colony-stimulating factor (GM-CSF) is an important hematopoietic cytokine that exerts its effects by interaction with the GM-CSF receptor (GMR) on the surface of responsive cells. The GM-CSF receptor consists of two subunits: GMR, which binds GM-CSF with low affinity, and GMRβ, which lacks intrinsic ligand-binding capability but complexes with GMR to form a high-affinity receptor (GMR/β). We conducted dynamic kinetic analyses of GM-CSF receptors to define the role of GMRβ in the interaction of ligand and receptor. Our data show that GMR/β exhibits a higher kon than GMR, indicating that GMRβ facilitates ligand acquisition to the binding pocket. Heterogeneity with regard to GM-CSF dissociation from GMR/β points to the presence of loose and tight ligand-receptor complexes in high-affinity binding. Although the loose complex has a koff similar to GMR, the lower koffindicates that GMRβ inhibits GM-CSF release from the tight receptor complex. The two rates of ligand dissociation may provide for discrete mechanisms of interaction between GM-CSF and its high-affinity receptor. These results show that the β subunit functions to stabilize ligand binding as well as to facilitate ligand acquisition.

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10

Danilowicz, Claudia, Derek Greenfield e Mara Prentiss. "Dissociation of Ligand−Receptor Complexes Using Magnetic Tweezers". Analytical Chemistry 77, n. 10 (maggio 2005): 3023–28. http://dx.doi.org/10.1021/ac050057+.

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Tesi sul tema "Receptor-ligand complexes"

1

Patel, Amesh Babubhai. "Biophysical and computational investigations into receptor-ligand complexes". Thesis, University of Nottingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435998.

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Wang, Xiang. "Computational studies of melanocortin receptor system and channel function in glutamine-dependent amidotransferases". [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0001072.

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Bishop, Benjamin F. "Structural and functional characterisation of hedgehog ligand-receptor complexes". Thesis, University of Oxford, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.642625.

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Members of the Hedgehog (HH) family of morphogenic signalling molecules are key mediators of many fundamental processes in embryonic development. A relatively small change in HH concentration results in the specification of distinct cell types. Such fine-tuning necessitates a range of regulatory cell-surface proteins to control the concentration of HH to which responding cells are exposed. This thesis focuses on the structural and functional characterisation of three human extracellular modulators of the HH pathway, namely the hedgehog-interacting protein HHIP, the glypican GPC3 and the Growth Arrest Specific 1 (GAS1). Cell culture robot protocols were developed to allow large-scale expression of these targets in mammalian cells (Chapter 3). In Chapter 4, the structure of the HH antagonist HHIP alone and in complex with HH ligands is described. These studies combined with functional experiments reveal a binding mode distinct from previously defined ligand interaction sites, with the HH metal-binding sites playing key roles. The structural and functional analysis of GPC3, another negative HH regulator, is described in Chapter 5. Binding studies suggest that the GPC3 core domain does not bind directly to SHH and that the GPC3-attched heparan sulphate chains play an important role in HH regulation. Chapter 6 reveals crystal structures of the GAS 1 ectodomain, a HH agonist, allowing comparison to glial cell line-derived neurotrophic factor receptors, the identification of an unexpected ligand and mapping of the HH binding site. In summary, this work provides insights into the extracellular modulation of HH signalling and extends our current knowledge of this fundamental signalling pathway. It also offers a model to explain how both agonists and antagonists can adopt similar mechanisms of HH binding.

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Coonan, Jason R. "Regulation of neural connectivity by the EphA4 receptor tyrosine kinase /". Connect to thesis, 2001. http://eprints.unimelb.edu.au/archive/00000727.

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5

Nahas, Roger I. "Synthesis and structure-activity relationship of a series of sigma receptor ligands". Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4840.

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Thesis (Ph. D.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on February 26, 2008) Vita. Includes bibliographical references.

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6

Read, Stuart Hamilton. "Production and function of a soluble c-Kit molecule". Title page, abstract and contents only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09phr2845.pdf.

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"Research conducted at the Department of Haematology, Hanson Centre for Cancer Research, Institute of Medical and Veterinary Science."--T.p. Includes bibliographical references (leaves 170-214). Elevated levels of receptor tyrosine kinases have been implicated in carcinogenesis. It is possible that high expression of c-Kit by the leukaemic cell provides them with a growth advantage over their normal counterparts in the bone marrow microenvironment. Thus, a means of inhibiting the interaction of c-Kit on these cells with ligand Steel Factor may remove proliferation and survival signals. Main aim of the study was to produce a biological inhibitor of this interaction and evaluate its ability to prevent ligand Steel Factor from binding to c-Kit on live cells.

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7

Lengqvist, Johan. "Native protein mass spectrometry of nuclear receptor-ligand and enzyme-substrate complexes /". Stockholm, 2004. http://diss.kib.ki.se/2004/91-7140-116-4/.

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8

Smith, Mark Edward. "Molecular wires : syntheses, electrochemistry and properties of metal complexes containing carbon chains /". Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09PH/09phs654.pdf.

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Thesis (Ph.D.)--University of Adelaide, Dept. of Chemistry, 2002.
"September 2002" Includes as appendix: a list of publications by the author arising from this work; and, copies of some published journal articles. Includes bibliographical references.

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9

Yamamoto, Izumi. "Structure-function studies of GABA-C receptor ligands". Thesis, The University of Sydney, 2012. https://hdl.handle.net/2123/28927.

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Throughout the central nervous system (CNS), the Cys-loop superfamily of ligand-gated ion channels {LGICs), including nicotinic acetylcholine, serotonin type-3A, strychnine-sensitive glycine and y-aminobutyric acid A/C receptors, play important roles in synaptic transmission by converting chemical signals into electric signals. Designing potent and subtype-selective ligands with therapeutic value requires knowledge about how ligands interact with their binding sites. y-Aminobutyric acid (GABA) is the predominant inhibitory neurotransmitter in the mammalian CNS and its binding modes at GABA receptors have not been fully elucidated. GABAc receptors consist of p subunits (p1-p3) and they are known to form homomeric receptors. The five subunits are arranged around a central chloride selective ion channel pore. Each subunit contains a large extracellular N-terminal domain, four transmembrane domains {Ml-M4) of which the second (M2) lines the channel pore and a large M3-M4 intracellular loop. The orthosteric binding site is located at the interface between two subunits in the N-terminal domain and the key residues for ligand binding are found at the five discontinuous loops (A-E). This thesis describes how ligand binding and receptor gating are closely related and explores the effect of receptor conformational changes upon ligand binding. A series of point mutations in the N-terminal domain of the GABAc p1 receptor were created and expressed in Xenopus oocytes. The mutant receptors were then examined using a range of pharmacological tools to probe function which was measured using the two-electrode voltage clamp method. The GABA binding mode was explored at GABA receptors using the enantiomers of 3-fluoro-y-aminobutyric acid (3F-GABA) and stereoisomers of 2,3-difluoro-4-aminobutyric acids as conformational probes. Both enantiomers of 3FGABA were full agonists, with the R-3F-GABA being approximately 3-fold more potent than 5-3F-GABA at GABAc receptors. In contrast, both enantiomers were partial agonists with similar efficacy and potency at GABAA receptors. These results suggest a different GABA binding mode at GABAc receptors to that found in the related but pharmacologically distinct GABAA receptors. The effect of the different stereoisomers of 2,3-difluoro-4-aminobutyric acids were also examined at GABAA, GABA8 and GABAc receptors. In the study, two enantiomeric GABAc receptor ligands were identified, one of which is an agonist (25,35-2,3-difluoro-4-aminobutyric acid) while the other is an antagonist (2R,3R-2,3-difluoro-4-aminobutyric acid). 4-Amino-3-hydroxybutanoic acid (GABOB) is an endogenous ligand found in the CNS in mammals and a metabolite of GABA. Homology modeling of the GABAc Pi receptor revealed a potential hydrogen (H-bond) interaction between the hydroxyl group of GABOB and threonine 244 (T244) located on loop C of the ligand binding site. Using site-directed mutagenesis, the effect of mutating T244 on the efficacy and pharmacology of GABOB and various ligands were examined. It was found that mutating T244 to amino acids that lacked a hydroxyl group in the side chain produced GABA insensitive receptors. Only by mutating PiT244 to serine (PiT2445) produced a GABA responsive receptor, albeit 39-fold less sensitive to GABA than Pi wild-type. It was also found that this mutation also changed the activity of GABAc receptor partial agonists, muscimol and imidazole-4-acetic acid (I4AA). At the concentrations tested, both muscimol and I4AA antagonized the currents produced by GABA at PiT2445 mutant receptors (Muscimol: PiWild-type, EC50 = 1.4 µM; PiT2445, IC50 = 32.8 µM. I4AA: Pi wild-type, EC50 = 8.6 µM; PiT2445, IC50 = 21.4 µM). This indicates that T244 is predominantly involved in channel gating. R-(-)-GABOB and 5-(+)-GABOB are full agonists at Pi wild-type receptors. In contrast, R-(-)-GABOB was a weak partial agonist at PiT2445 (lmM activates 26 % of the current produced by GABA ECso versus Pi wild-type, EC50 = 19 µM; lmax 100%), and 5-(+)-GABOB was a competitive antagonist at PiT2445 receptors (Pi wild-type, EC50 = 45 µM versus PiT2445, IC50 = 417.4 µM, Ks = 204 µM). This highlights that the interaction of GABOB with T244 is enantioselective. In contrast, the potencies of a range of antagonists tested, 3-aminopropyl(methyl)phosphinic acid (3-APMPA), 3-aminopropylphosphonic acid (3-APA), 5- and R-(3-amino-2-hydroxypropyl)methylphosphinic acid (5-(-)-CGP44532 and R-(+)-CGP44533), were not altered. This suggests that T244 is not critical for antagonist binding. Receptor gating is dynamic and this study highlights the role of loop C in agonist-evoked receptor activation, coupling agonist binding to channel gating. Ligands acting on receptors are considered to induce a conformational change within the ligand-binding site by interacting with specific amino acids. In this study, tyrosine 102 (Y102) located in the GABA binding site of the Pi subunit of the GABAc receptor was mutated to alanine (piY102A), serine (piY102S) and cysteine (piY102C) to assess the role of this amino acid plays on the action of 12 known and 2 novel antagonists. Of the mutated receptors, piY102S was constitutively active providing an opportunity to assess the activity of the antagonists on Pi receptors with a proportion of receptors existing in the open conformational state compared to those existing predominantly in the closed conformational state (pi wild-type, PiY102C and PiY102A). It was found that the majority of antagonists studied were able to inhibit the constitutive activity displayed by PiY1025, thus displaying inverse agonist activity. The exception was (±)-4-aminocyclopent-1-enecarboxamide ((±)-4-ACPAM) not exhibiting any inverse agonist activity, but acting explicitly on the closed conformational state of Pi receptors. It was also found that GABA antagonists were more potent at the closed compared to the open conformational states of Pi receptors suggesting that they may act by stabilizing the closed conformational state and thus reducing activation by agonists. Furthermore, of the antagonists tested, Y102 was found to have the greatest influence on the antagonist activity of gabazine (SR-95531) and its analogue (SR-95813). Our GABAc Pi receptor homology model identified a novel cavity, which extended beyond the GABA binding site. The model predicted phenylalanine 124(F124), one of the residues lining the cavity, was pointing towards the orthosteric binding site. In this study, F124 was mutated to various amino acids and only a modest effect on receptor pharmacology was observed. However, the mutations had a significant effect on the channel deactivation rate ('toeactivation)- This finding suggests that F124 may play a role in channel gating or stabilizing the open conformation of the receptor. Designing potent selective agents are the key for the further understanding of the physiological roles of GABAc receptors. Gabazine (SR-95531) is a potent GABAA receptor competitive antagonist. In this study, a series of novel gabazine analogues were tested at GABAA and GABAc receptors. Of the compounds studied, (p)-methoxy analogue without the butyric acid side-chain was 20-fold more potent at GABAc over GABAA receptors. As there was no butyric acid side chain, it is suggested that the carboxylic acid is not important for gabazine activity at this receptor. Establishing the structure-activity relationship based on this analogue will facilitate the development of selective GABAc receptor antagonists with possible physiological effects including memory-enhancement. Overall, our studies describe agonist and GABAc receptor antagonist induced conformational changes within the ligand binding site. Our findings also highlight the dynamic nature of receptor gating, initiated by ligand binding at a site physically distinct from the ion channel.

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Nervall, Martin. "Binding Free Energy Calculations on Ligand-Receptor Complexes Applied to Malarial Protease Inhibitors". Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8338.

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Libri sul tema "Receptor-ligand complexes"

1

S, Zhorov B., a cura di. Ligand-ret͡s︡eptornye vzaimodeĭstvii͡a︡ v molekuli͡a︡rnoĭ fiziologii. Sankt-Peterburg: "Nauka", 1994.

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Health Effects Research Laboratory (Research Triangle Park, N.C.), a cura di. Characterization of the Ah receptor: Project summary. Research Triangle Park, NC: U.S. Environmental Protection Agency, Health Effects Research Laboratory, 1989.

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Safe, Stephen H. Characterization of the Ah receptor: Project summary. Research Triangle Park, NC: U.S. Environmental Protection Agency, Health Effects Research Laboratory, 1989.

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4

C, Hulme E., a cura di. Receptor-ligand interactions: A practical approach. Oxford [England]: IRL Press at Oxford University Press, 1992.

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5

A, Burgen, e Barnard Eric A. 1927-, a cura di. Receptor subunits and complexes. Cambridge [England]: Cambridge University Press, 1992.

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6

Browne, M. J. Recombinant cells surface receptors: Focal point for therapeutic intervention. Austin, Tex: R.G. Landes Co., 1996.

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7

Hestermann, Eli V. Mechanisms of action for aryl hydrocarbon receptor ligands in the PLHC-1 cell line. Cambridge, Mass: Massachusetts Institute of Technology, 2000.

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1961-, Keen Mary, a cura di. Receptor binding techniques. Totowa, N.J: Humana Press, 1999.

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9

P, Davenport Anthony, a cura di. Receptor binding techniques. 2^a ed. Totowa, N.J: Humana Press, 2005.

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1957-, Russell David W., e Mangelsdorf David J. 1958-, a cura di. Nuclear receptors. Amsterdam: Elsevier Academic Press, 2002.

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Capitoli di libri sul tema "Receptor-ligand complexes"

1

Vermeer, B. J., A. M. Mommaas-Kienhuis, M. C. Wijsman, J. J. Emeis e M. Ponec. "A Model for Morphological Studies on Ligand-Receptor Complexes". In Skin Models, 315–26. Berlin, Heidelberg: Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-70387-4_35.

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Pogozheva, Irina D., Magdalena J. Przydzial e Henry I. Mosberg. "Homology Modeling of Opioid Receptor-Ligand Complexes Using Experimental Constraints". In Drug Addiction, 559–84. New York, NY: Springer New York, 2008. http://dx.doi.org/10.1007/978-0-387-76678-2_33.

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Lozoya, Estrella, Maria Isabel Loza e Ferran Sanz. "Modelling of the 5-HT2A Receptor and Its Ligand Complexes". In Molecular Modeling and Prediction of Bioactivity, 355–56. Boston, MA: Springer US, 2000. http://dx.doi.org/10.1007/978-1-4615-4141-7_74.

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Limbird, Lee E. "Biochemical Correlates of the Topographical Fate of Ligand-Receptor Complexes". In Cell Surface Receptors: A Short Course on Theory and Methods, 159–94. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4757-1882-9_6.

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Perales, Jose C., Thomas Ferkol, Maria Molas e Richard W. Hanson. "An evaluation of receptor-mediated gene transfer using synthetic DNA-ligand complexes". In EJB Reviews 1994, 209–20. Berlin, Heidelberg: Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-642-79502-2_16.

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Krishna, N. Rama, e V. Jayalakshmi. "Quantitative Analysis of STD-NMR Spectra of Reversibly Forming Ligand–Receptor Complexes". In Topics in Current Chemistry, 15–54. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/128_2007_144.

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Wang, Andrew H. J., Yen-Chywan Liaw, Howard Robinson e Yi-Gui Gao. "Mutual Conformational Adaptation of Both Ligand and Receptor in Antitumor Drug-DNA Complexes". In The Jerusalem Symposia on Quantum Chemistry and Biochemistry, 1–21. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-011-3728-7_1.

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Khashan, Raed S. "Generating “Fragment-Based Virtual Library” Using Pocket Similarity Search of Ligand–Receptor Complexes". In Methods in Molecular Biology, 23–29. New York, NY: Springer New York, 2015. http://dx.doi.org/10.1007/978-1-4939-2486-8_3.

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Limbird, Lee E. "The Topographical Fate of Ligand-Receptor Complexes as Reflected by the Properties of Ligand Binding to Intact Cells". In Cell Surface Receptors: A Short Course on Theory and Methods, 201–32. Boston, MA: Springer US, 1996. http://dx.doi.org/10.1007/978-1-4613-1255-0_6.

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Rejto, Paul A., Gennady M. Verkhivker, Daniel K. Gehlhaar e Stephan T. Freer. "New trends in computational structure prediction of ligand-protein complexes for receptor-based drug design". In Computer Simulation of Biomolecular Systems, 451–65. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-017-1120-3_17.

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Atti di convegni sul tema "Receptor-ligand complexes"

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Ates, Abdullah, Baris Baykant Alagoz, Aleksei Tepljakov, Eduard Petlenkov, Celaledddin Yeroglu, Aleksei Kuznetsov e Innokenti Sobolev. "Fractional Order Model Identification of Receptor-Ligand Complexes Formation by Equivalent Electrical Circuit Modeling". In 2019 International Artificial Intelligence and Data Processing Symposium (IDAP). IEEE, 2019. http://dx.doi.org/10.1109/idap.2019.8875913.

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Wallrabe, Horst, Ammasi Periasamy, Almut Burchard e Margarida Barroso. "Comparing different FRET techniques to measure clustering of receptor-ligand complexes in endocytic membranes". In Biomedical Optics 2003, a cura di Ammasi Periasamy e Peter T. C. So. SPIE, 2003. http://dx.doi.org/10.1117/12.485606.

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Fanelli, F., M. C. Menziani, M. Cocchi, A. Carotti e P. G. De Benedetti. "Theoretical approaches to quantitative structure-activity relationship (QSAR) analysis of M1-muscarinic receptor-ligand complexes". In The first European conference on computational chemistry (E.C.C.C.1). AIP, 1995. http://dx.doi.org/10.1063/1.47825.

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Rudkouskaya, Alena, Nattawut Sinsuebphon, Xavier Intes, Joseph E. Mazurkiewicz e Margarida Barroso. "Fluorescence lifetime FRET imaging of receptor-ligand complexes in tumor cells in vitro and in vivo". In SPIE BiOS, a cura di Ammasi Periasamy, Peter T. C. So, Karsten König e Xiaoliang S. Xie. SPIE, 2017. http://dx.doi.org/10.1117/12.2258231.

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Petrović, Đorđe, Maja Đukić, Edina Avdović, Danijela Stojković, Verica Jevtić, Sandra Jovičić Milić e Marina Vesović. "DNA binding and molecular docking of four palladium(II) complexes with O,O’-dialkyl esters of (S,S)-propylenediamine-N,N’-di-2-(2-benzyl) acetic acid". In 2nd International Conference on Chemo and Bioinformatics. Institute for Information Technologies, University of Kragujevac, 2023. http://dx.doi.org/10.46793/iccbi23.539p.

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The antitumor activity of platinum-based complexes still captures the attention of scientists and new potential drugs are being synthesized and investigated. Although complexes of palladium(II) ion show less cytotoxicity compared to platinum(II) complexes due to the high reactivity of the palladium center, research in this field has continued and many authors have found that auxiliary chelating ligands can improve complex stability and their cytotoxicity. As a consequence of rapid ligand exchange, the probability of palladium(II) complexes reaching the biological target in organisms seems to be low. The use of chelating ligands has been proposed as a solution to this problem. In our paper, the interactions of new palladium(II) complexes with ethyl (C1), propyl (C2), buthyl (C3) and pentyl (C4) ester of (S,S)-propylenediamine-N,N’-di-2-(2-benzyl) acetic acid with calf thymus DNA (CT-DNA) was studied by fluorescence spectroscopy and electronic absorption spectroscopy, while molecular docking simulations were used to examine the inhibitor efficiency of C1-C4 against DNA receptor.

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Chesla, Scott E., e Cheng Zhu. "Validation and Accuracy Assessment of the Micropipet Piconewton Force Transducer". In ASME 1996 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/imece1996-1112.

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Abstract In processes that involve interactions of the cell with its environment, adhesion is often the initiating event for a particular cellular function. Adhesion assays are thus among the first to be used to characterize the essential molecular complexes involved. Recently, increasing attention has been focused on single molecular binding between a particular cellular receptor class and its ligand. Elucidation of the forces involved in single bonds can lead to better understanding of how cells deal with their environment via controlling the specificity and strength of their adhesions.

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Wallrabe, Horst, Masilamani Elangovan, Almut Burchard, Ammasi Periasamy e Margarida Barroso. "FRET microscopy reveals clustered distribution of co-internalized receptor-ligand complexes in the apical recycling endosome of polarized epithelial MDCK cells". In International Symposium on Biomedical Optics, a cura di Ammasi Periasamy e Peter T. C. So. SPIE, 2002. http://dx.doi.org/10.1117/12.470677.

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Wallrabe, Horst K., e Margarida Barroso. "FRET reveals the organization of different receptor-ligand complexes (polymeric IgA-R and Transferrin-R) in endocytic membranes of polarized MDCK cells". In Biomedical Optics 2004, a cura di Ammasi Periasamy e Peter T. C. So. SPIE, 2004. http://dx.doi.org/10.1117/12.539755.

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Wallrabe, Horst, Masilamani Elangovan, Almut Burchard e Margarida Barroso. "Energy transfer efficiency based on one-and two-photon FRET microscopy differentiates between clustered and random distribution of membrane-bound receptor-ligand complexes". In International Symposium on Biomedical Optics, a cura di Ammasi Periasamy e Peter T. C. So. SPIE, 2002. http://dx.doi.org/10.1117/12.470703.

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Brewer, Bryson M., Yandong Gao, Rebecca M. Sappington e Deyu Li. "Microfluidic Molecular Trap: Probing Extracellular Signaling by Selectively Blocking Exchange of Specific Molecules in Cell-Cell Interactions". In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-64489.

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Communication among cell populations is achieved via a wide variety of soluble, extracellular signaling molecules [1]. In order to investigate the role of specific molecules in a cellular process, researchers often utilize in vitro cell culture techniques in which the molecule under question has been removed from the signaling pathway. Traditionally, this has been accomplished by eliminating the gene in the cell that is responsible for coding the targeted ligand/receptor by using modern DNA technology such as gene knockout; however, this process is expensive, time-consuming, and labor intensive. Previously, we have demonstrated a microfluidic platform that uses a semi-permeable barrier with embedded receptor-coated nanoparticles to selectively remove a specific molecule or ligand from the extracellular signaling pathway in a cell co-culture environment [2]. This initial proof-of-principle was conducted using biotinylated nanoparticles and fluorescently tagged avidin molecules, as the avidin/biotin complex is the strongest known non-covalent interaction between a protein and a ligand (Dissociation constant kd = 10−15 M). Also, the trap was only effective for short time periods (<15 min) because the high concentration of fluorescently tagged avidin molecules required for visualization quickly saturated the barrier. However, nearly all biologically relevant ligand-receptor interactions have lower binding affinities than the avidin-biotin complex, with dissociation constants that are larger by several orders of magnitude. In addition, many in vitro cell culture experiments are conducted over multiple hours or days. Thus, a practically useful molecular trap device must be able to operate in a lower binding affinity regime while also lasting for extended time periods. Here we present results in which a biotinylated-particle barrier was used to successfully block lower concentrations of fluorescently tagged avidin for multiple days, showcasing the applicability of the device for long term experiments. In addition, we introduce a modified molecular trap in which the protein A/goat IgG complex was used to demonstrate the effectiveness of the platform for lower binding affinity protein-ligand interactions. These results indicate the potential usefulness of the microfluidic molecular trap platform for probing extracellular signaling pathways.

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Rapporti di organizzazioni sul tema "Receptor-ligand complexes"

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Rafaeli, Ada, e Russell Jurenka. Molecular Characterization of PBAN G-protein Coupled Receptors in Moth Pest Species: Design of Antagonists. United States Department of Agriculture, dicembre 2012. http://dx.doi.org/10.32747/2012.7593390.bard.

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The proposed research was directed at determining the activation/binding domains and gene regulation of the PBAN-R’s thereby providing information for the design and screening of potential PBAN-R-blockers and to indicate possible ways of preventing the process from proceeding to its completion. Our specific aims included: (1) The identification of the PBAN-R binding domain by a combination of: (a) in silico modeling studies for identifying specific amino-acid side chains that are likely to be involved in binding PBAN with the receptor and; (b) bioassays to verify the modeling studies using mutant receptors, cell lines and pheromone glands (at tissue and organism levels) against selected, designed compounds to confirm if compounds are agonists or antagonists. (2) The elucidation ofthemolecular regulationmechanisms of PBAN-R by:(a) age-dependence of gene expression; (b) the effect of hormones and; (c) PBAN-R characterization in male hair-pencil complexes. Background to the topic Insects have several closely related G protein-coupled receptors (GPCRs) belonging to the pyrokinin/PBAN family, one with the ligand pheromone biosynthesis activating neuropeptide or pyrokinin-2 and another with diapause hormone or pyrokinin-1 as a ligand. We were unable to identify the diapause hormone receptor from Helicoverpa zea despite considerable effort. A third, related receptor is activated by a product of the capa gene, periviscerokinins. The pyrokinin/PBAN family of GPCRs and their ligands has been identified in various insects, such as Drosophila, several moth species, mosquitoes, Triboliumcastaneum, Apis mellifera, Nasoniavitripennis, and Acyrthosiphon pisum. Physiological functions of pyrokinin peptides include muscle contraction, whereas PBAN regulates pheromone production in moths plus other functions indicating the pleiotropic nature of these ligands. Based on the alignment of annotated genomic sequences, the primary and secondary structures of the pyrokinin/PBAN family of receptors have similarity with the corresponding structures of the capa or periviscerokinin receptors of insects and the neuromedin U receptors found in vertebrates. Major conclusions, solutions, achievements Evolutionary trace analysisof receptor extracellular domains exhibited several class-specific amino acid residues, which could indicate putative domains for activation of these receptors by ligand recognition and binding. Through site-directed point mutations, the 3rd extracellular domain of PBAN-R was shown to be critical for ligand selection. We identified three receptors that belong to the PBAN family of GPCRs and a partial sequence for the periviscerokinin receptor from the European corn borer, Ostrinianubilalis. Functional expression studies confirmed that only the C-variant of the PBAN-R is active. We identified a non-peptide agonist that will activate the PBAN-receptor from H. zea. We determined that there is transcriptional control of the PBAN-R in two moth species during the development of the pupa to adult, and we demonstrated that this transcriptional regulation is independent of juvenile hormone biosynthesis. This transcriptional control also occurs in male hair-pencil gland complexes of both moth species indicating a regulatory role for PBAN in males. Ultimate confirmation for PBAN's function in the male tissue was revealed through knockdown of the PBAN-R using RNAi-mediated gene-silencing. Implications, both scientific and agricultural The identification of a non-peptide agonist can be exploited in the future for the design of additional compounds that will activate the receptor and to elucidate the binding properties of this receptor. The increase in expression levels of the PBAN-R transcript was delineated to occur at a critical period of 5 hours post-eclosion and its regulation can now be studied. The mysterious role of PBAN in the males was elucidated by using a combination of physiological, biochemical and molecular genetics techniques.

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Rafaeli, Ada, Russell Jurenka e Chris Sander. Molecular characterisation of PBAN-receptors: a basis for the development and screening of antagonists against Pheromone biosynthesis in moth pest species. United States Department of Agriculture, gennaio 2008. http://dx.doi.org/10.32747/2008.7695862.bard.

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The original objectives of the approved proposal included: (a) The determination of species- and tissue-specificity of the PBAN-R; (b) the elucidation of the role of juvenile hormone in gene regulation of the PBAN-R; (c) the identificationof the ligand binding domains in the PBAN-R and (d) the development of efficient screening assays in order to screen potential antagonists that will block the PBAN-R. Background to the topic: Moths constitute one of the major groups of pest insects in agriculture and their reproductive behavior is dependent on chemical communication. Sex-pheromone blends are utilised by a variety of moth species to attract conspecific mates. In most of the moth species sex-pheromone biosynthesis is under circadian control by the neurohormone, PBAN (pheromone-biosynthesis-activating neuropeptide). In order to devise ideal strategies for mating disruption/prevention, we proposed to study the interactions between PBAN and its membrane-bound receptor in order to devise potential antagonists. Major conclusions: Within the framework of the planned objectives we have confirmed the similarities between the two Helicoverpa species: armigera and zea. Receptor sequences of the two Helicoverpa spp. are 98% identical with most changes taking place in the C-terminal. Our findings indicate that PBAN or PBAN-like receptors are also present in the neural tissues and may represent a neurotransmitter-like function for PBAN-like peptides. Surprisingly the gene encoding the PBAN-receptor was also present in the male homologous tissue, but it is absent at the protein level. The presence of the receptor (at the gene- and protein-levels), and the subsequent pheromonotropic activity are age-dependent and up-regulated by Juvenile Hormone in pharate females but down-regulated by Juvenile Hormone in adult females. Lower levels of pheromonotropic activity were observed when challenged with pyrokinin-like peptides than with HezPBAN as ligand. A model of the 3D structure of the receptor was created using the X-ray structure of rhodopsin as a template after sequence alignment of the HezPBAN-R with several other GPCRs and computer simulated docking with the model predicted putative binding sites. Using in silico mutagenesis the predicted docking model was validated with experimental data obtained from expressed chimera receptors in Sf9 cells created by exchanging between the three extracellular loops of the HezPBAN-R and the Drosophila Pyrokinin-R (CG9918). The chimera receptors also indicated that the 3ʳᵈ extracellular loop is important for recognition of PBAN or Diapause hormone ligands. Implications: The project has successfully completed all the objectives and we are now in a position to be able to design and screen potential antagonists for pheromone production. The successful docking simulation-experiments encourage the use of in silico experiments for initial (high-throughput) screening of potential antagonists. However, the differential responses between the expressed receptor (Sf9 cells) and the endogenous receptor (pheromone glands) emphasize the importance of assaying lead compounds using several alternative bioassays (at the cellular, tissue and organism levels). The surprising discovery of the presence of the gene encoding the PBAN-R in the male homologous tissue, but its absence at the protein level, launches opportunities for studying molecular regulation pathways and the evolution of these GPCRs. Overall this research will advance research towards the goal of finding antagonists for this important class of receptors that might encompass a variety of essential insect functions.

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Eyal, Yoram, e Sheila McCormick. Molecular Mechanisms of Pollen-Pistil Interactions in Interspecific Crossing Barriers in the Tomato Family. United States Department of Agriculture, maggio 2000. http://dx.doi.org/10.32747/2000.7573076.bard.

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During the evolutionary process of speciation in plants, naturally occurring barriers to reproduction have developed that affect the transfer of genes within and between related species. These barriers can occur at several different levels beginning with pollination-barriers and ending with hybrid-breakdown. The interaction between pollen and pistils presents one of the major barriers to intra- and inter-specific crosses and is the focus of this research project. Our long-term goal in this research proposal was defined to resolve questions on recognition and communication during pollen-pistil interactions in the extended tomato family. In this context, this work was initiated and planned to study the potential involvement of tomato pollen-specific receptor-like kinases (RLK's) in the interaction between pollen and pistils. By special permission from BARD the objectives of this research were extended to include studies on pollen-pistil interactions and pollination barriers in horticultural crops with an emphasis on citrus. Functional characterization of 2 pollen-specific RLK's from tomato was carried out. The data shows that both encode functional kinases that were active as recombinant proteins. One of the kinases was shown to accumulate mainly after pollen germination and to be phosphorylated in-vitro in pollen membranes as well as in-vivo. The presence of style extract resulted in dephosphorylation of the RLK, although no species specificity was observed. This data implies a role for at least one RLK in pollination events following pollen germination. However, a transgenic plant analysis of the RLK's comprising overexpression, dominant-negative and anti-sense constructs failed to provide answers on their role in pollination. While genetic effects on some of the plants were observed in both the Israeli and American labs, no clear functional answers were obtained. An alternative approach to addressing function was pursued by screening for an artificial ligand for the receptor domain using a peptide phage display library. An enriched peptide sequence was obtained and will be used to design a peptide-ligand to be tested for its effect o pollen germination and tube growth. Self-incompatibility (SI) in citrus was studied on 3 varieties of pummelo. SI was observed using fluorescence microscopy in each of the 3 varieties and compatibility relations between varieties was determined. An initial screen for an S-RNase SI mechanism yielded only a cDNA homologous to the group of S-like RNases, suggesting that SI results from an as yet unknown mechanism. 2D gel electrophoresis was applied to compare pollen and style profiles of different compatibility groups. A "polymorphic" protein band from style extracts was observed, isolated and micro-sequenced. Degenerate primers designed based on the peptide sequence date will be used to isolate the relevant genes i order to study their potential involvement in SI. A study on SI in the apple cultivar Top red was initiated. SI was found, as previously shown, to be complete thus requiring a compatible pollinator variety. A new S-RNase allele was discovered fro Top red styles and was found to be highly homologous to pear S-RNases, suggesting that evolution of these genes pre-dated speciation into apples and pears but not to other Rosaceae species. The new allele provides molecular-genetic tools to determine potential pollinators for the variety Top red as well as a tool to break-down SI in this important variety.

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Chen, Yona, Jeffrey Buyer e Yitzhak Hadar. Microbial Activity in the Rhizosphere in Relation to the Iron Nutrition of Plants. United States Department of Agriculture, ottobre 1993. http://dx.doi.org/10.32747/1993.7613020.bard.

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Iron is the fourth most abundant element in the soil, but since it forms insoluble hydroxides at neutral and basic pH, it often falls short of meeting the basic requirements of plants and microorganisms. Most aerobic and facultative aerobic microorganisms possess a high-affinity Fe transport system in which siderophores are excreted and the consequent Fe complex is taken up via a cognate specific receptor and a transport pathway. The role of the siderophore in Fe uptake by plants and microorganisms was the focus of this study. In this research Rhizopus arrhizus was found to produce a novel siderophore named Rhizoferrin when grown under Fe deficiency. This compound was purified and its chemical structure was elucidated. Fe-Rhizoferrin was found to alleviate Fe deficiency when applied to several plants grown in nutrient solutions. It was concluded that Fe-Rhizoferrin is the most efficient Fe source for plants when compared with other among microbial siderophores known to date and its activity equals that of the most efficient synthetic commercial iron fertilizer-Fe EDDHA. Siderophores produced by several rhizosphere organisms including Rhizopus Pseudomonas were purified. Monoclonal antibodies were produced and used to develop a method for detection of the siderophores produced by plant-growth-promoting microorganisms in barley rhizosphere. The presence of an Fe-ferrichrome uptake in fluorescent Pseudomonas spp. was demonstrated, and its structural requirements were mapped in P. putida with the help of biomimetic ferrichrome analogs. Using competition experiments, it was shown that FOB, Cop B and FC share at least one common determinant in their uptake pathway. Since FC analogs did not affect FOB or Cop-mediated 55Fe uptake, it could be concluded that these siderophores make use of a different receptor(s) than FC. Therefore, recognition of Cop, FOB and FC proceeds through different receptors having different structural requirements. On the other hand, the phytosiderophores mugineic acid (MA and DMA), were utilized indirectly via ligand exchange by P. putida. Receptors from different biological systems seem to differ in their structural requirements for siderophore recognition and uptake. The design of genus- or species-specific drugs, probes or chemicals, along with an understanding of plant-microbe and microbe-microbe relationships as well as developing methods to detect siderophores using monoclonal antibodies are useful for manipulating the composition of the rhizosphere microbial population for better plant growth, Fe-nutrition and protection from diseases.

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Epel, Bernard, e Roger Beachy. Mechanisms of intra- and intercellular targeting and movement of tobacco mosaic virus. United States Department of Agriculture, novembre 2005. http://dx.doi.org/10.32747/2005.7695874.bard.

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To cause disease, plant viruses must replicate and spread locally and systemically within the host. Cell-to-cell virus spread is mediated by virus-encoded movement proteins (MPs), which modify the structure and function of plasmodesmata (Pd), trans-wall co-axial membranous tunnels that interconnect the cytoplasm of neighboring cells. Tobacco mosaic virus (TMV) employ a single MP for cell- cell spread and for which CP is not required. The PIs, Beachy (USA) and Epel (Israel) and co-workers, developed new tools and approaches for study of the mechanism of spread of TMV that lead to a partial identification and molecular characterization of the cellular machinery involved in the trafficking process. Original research objectives: Based on our data and those of others, we proposed a working model of plant viral spread. Our model stated that MPᵀᴹⱽ, an integral ER membrane protein with its C-terminus exposed to the cytoplasm (Reichel and Beachy, 1998), alters the Pd SEL, causes the Pd cytoplasmic annulus to dilate (Wolf et al., 1989), allowing ER to glide through Pd and that this gliding is cytoskeleton mediated. The model claimed that in absence of MP, the ER in Pd (the desmotubule) is stationary, i.e. does not move through the Pd. Based on this model we designed a series of experiments to test the following questions: -Does MP potentiate ER movement through the Pd? - In the presence of MP, is there communication between adjacent cells via ER lumen? -Does MP potentiate the movement of cytoskeletal elements cell to cell? -Is MP required for cell-to-cell movement of ER membranes between cells in sink tissue? -Is the binding in situ of MP to RNA specific to vRNA sequences or is it nonspecific as measured in vitro? And if specific: -What sequences of RNA are involved in binding to MP? And finally, what host proteins are associated with MP during intracellular targeting to various subcellular targets and what if any post-translational modifications occur to MP, other than phosphorylation (Kawakami et al., 1999)? Major conclusions, solutions and achievements. A new quantitative tool was developed to measure the "coefficient of conductivity" of Pd to cytoplasmic soluble proteins. Employing this tool, we measured changes in Pd conductivity in epidermal cells of sink and source leaves of wild-type and transgenic Nicotiana benthamiana (N. benthamiana) plants expressing MPᵀᴹⱽ incubated both in dark and light and at 16 and 25 ᵒC (Liarzi and Epel, 2005 (appendix 1). To test our model we measured the effect of the presence of MP on cell-to-cell spread of a cytoplasmic fluorescent probe, of two ER intrinsic membrane protein-probes and two ER lumen protein-probes fused to GFP. The effect of a mutant virus that is incapable of cell-to-cell spread on the spread of these probes was also determined. Our data shows that MP reduces SEL for cytoplasmic molecules, dilates the desmotubule allowing cell-cell diffusion of proteins via the desmotubule lumen and reduces the rate of spread of the ER membrane probes. Replicase was shown to enhance cell-cell spread. The data are not in support of the proposed model and have led us to propose a new model for virus cell-cell spread: this model proposes that MP, an integral ER membrane protein, forms a MP:vRNAER complex and that this ER-membrane complex diffuses in the lipid milieu of the ER into the desmotubule (the ER within the Pd), and spreads cell to cell by simple diffusion in the ER/desmotubule membrane; the driving force for spread is the chemical potential gradient between an infected cell and contingent non-infected neighbors. Our data also suggests that the virus replicase has a function in altering the Pd conductivity. Transgenic plant lines that express the MP gene of the Cg tobamovirus fused to YFP under the control the ecdysone receptor and methoxyfenocide ligand were generated by the Beachy group and the expression pattern and the timing and targeting patterns were determined. A vector expressing this MPs was also developed for use by the Epel lab . The transgenic lines are being used to identify and isolate host genes that are required for cell-to-cell movement of TMV/tobamoviruses. This line is now being grown and to be employed in proteomic studies which will commence November 2005. T-DNA insertion mutagenesis is being developed to identify and isolate host genes required for cell-to-cell movement of TMV.

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