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Dissertations / Theses on the topic 'G proteins'

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Published: 4 June 2021

Last updated: 1 August 2024

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1

Pateman, Cassandra Sophie Catherine. "RGS proteins and G protein signalling." Thesis, University of Warwick, 2002. http://wrap.warwick.ac.uk/2367/.

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The work within this thesis is concerned with the creation of a temperature-sensitive Schizosaccharomyces pombe marker protein, and the regulation of the pheromone communication system of Sz. pombe reporter strains by RGS proteins. There are a limited number of marker proteins available for use in the genetic manipulation of Sz. pombe, and the generation of a temperature-sensitive Ura4p was envisaged to expand the scope of carrying out sequential gene disruptions in the fission yeast. PCR-based mutagenesis was used to introduce mutations in the ura4 cassette, and a leucine to proline mutation identified at residue 261 in the ura4 open reading frame conferred a temperature-sensitive requirement for uracil. To demonstrate the use of the Ura4sp marker in gene disruption, the Sz. pombe irpl gene was disrupted with the ura4u cassette, and subsequently, the prkl gene was disrupted with the wild-type ura4 cassette. RGS proteins are a recently discovered family of proteins that negatively regulate G protein-coupled signalling pathways. This thesis describes the ability of mammalian RGS proteins to regulate the pheromone communication system of Sz. pombe reporter strains. Human RGS 1 and human RGS4 displayed the greatest ability to negatively regulate the Sz. pombe pheromone signalling pathway when expressed from multicopy expression vectors. Human RGS2, human RGS3, human RGS9-2 and murine RGS2 displayed lesser, varying abilities. Expression of human RGS 1 from single copy reduced signalling at low pheromone concentrations. Expression of human RGS4 from single copy was incapable of reducing pheromone-independent and pheromone-dependent signalling. This thesis also describes the search for gain-of-function RGS proteins. Two potential gain-of-function szRgslp mutants were previously identified, and these mutants were recreated. The two mutations identified (histidine to arginine at szRgslp residue 171 and valine to isoleucine at szRgslp residue 305) conferred gain-of-function szRgslp phenotypes in an sxa2:: ura4 reporter strain. Hydroxylamine treatment of the human RGS4 open reading frame resulted in the identification of a potential gain-of-function RGS4 mutant. The lysine to arginine mutation at huRGS4p residue 20 conferred a gain-of-function huRGS4p phenotype in an sxa2:: ura4 reporter strain.

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2

Nauli, Sehat. "Folding kinetics and redesign of Peptostreptococcal protein L and G /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/9237.

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3

Nguyen, Giang Huong. "A functional analysis of the human LPA₁G protein coupled receptor." Thesis, Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-06072004-131304/unrestricted/nguyen%5Fgiang%5Fh%5F200405%5Fms.pdf.

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4

Ghimire, Ganga D., ガンガＤ. ギミレ, Kenichiro Imai, 賢一郎今井, Fumitsugu Akazawa, 史嗣赤沢, Toshiyuki Tsuji, et al. "Physicochemical properties of amino acid sequences of G-proteins for understanding GPCR-G-protein coupling." Chem-Bio Informatics Society, 2006. http://hdl.handle.net/2237/9277.

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5

Drinnan, Suzane Loraine. "G proteins in the basal ganglia." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/28981.

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G proteins are alpha-beta-gamma heterotrimers in the resting state, bound to GDP and complexed with the unbound receptor. Once the receptor becomes occupied, the alpha subunit exchanges GDP for GTP, becomes activated, and dissociates from the receptor and can stimulate or inhibit many intracellular activities such as phosphorylation and channel conductance. For example, Gs and Golf alpha subunits stimulate and Gi alpha subunits inhibit adenylyl cyclase. Go alpha subunits are abundant in brain, but are of unknown function. cDNAs for the alpha subunit have been cloned. In order to examine the relative distributions of G proteins in the brain, we used in situ hybridization with radiolabelled synthetic oligonucleotide probes. By using a tyrosine hydroxylase antibody, we found that the dopaminergic neurons of the substantia nigra and the noradrenergic neurons of the locus ceruleus express mRNA for the alpha subunits for each of Gi, Go, and Gs. We noted a paucity of Gs mRNA in the striatum. This was surprising because the basal ganglia contain a dopamine-stimulated adenylyl cyclase activity which has been assumed to be transduced by Gs. Also, immunohistochemistry, immunoblotting, and cholera ADP-ribosylation indicated a very high level of Gs alpha-like protein in the striatum. In order to ascertain which specific G protein we were detecting, we made probes to a new G protein previously identified in the olfactory system. Golf is a stimulatory G protein with size and sequence characteristics similar to those of Gs. The cholera toxin ADP-ribosylation site and C-terminal region to which the antibody was made are identical. We made oligonucloetide probes to the translated and untranslated portions of Golf alpha. High levels Golf mRNA and protein were detected in the striatum and nucleus accumbens, in addition to the expected high levels in the olfactory tubercle. Northern blot studies indicated that Golf transcripts are approximately ten-fold more abundant than Gs alpha transcripts in the striatum. These data indicate that Golf in not an olfactory-specific G protein. It is also the major stimulatory G protein in the basal ganglia. The selective expression of high levels of Golf in dopamine-rich forebrain areas suggest that it may couple DI dopamine receptors to adenylyl cyclase. The role of Golf in dopaminergic neurotransmission and neuropsychiatric disease should be considered.
Medicine, Faculty of
Graduate

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6

Hodson, Elizabeth Anne Marie. "G protein regulation of phospholipase C in vascular smooth muscle." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390487.

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7

Song, Hongman. "The roles of the phosducin family proteins in the regulation of heterotrimeric G proteins in vertebrate photoreceptors." Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10413.

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Thesis (Ph. D.)--West Virginia University, 2009.
Title from document title page. Document formatted into pages; contains vi, 96 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

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8

Brownlie, Zoe. "Regulation of signal transduction by RGS4." Connect to e-thesis, 2007. http://theses.gla.ac.uk/124/.

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Thesis (Ph.D.) - University of Glasgow, 2007.
Ph.D. thesis submitted to the Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, 2007. Includes bibliographical references.

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9

Adhikari, Anirban. "Regulation of guanine nucelotide exchange in inhibitory G protein alpha subunit by activator of G protein signaling 3 and novel regulatory peptides." Embargoed access until after 12/19/2006, 2005. http://www4.utsouthwestern.edu/library/ETD/etdDetails.cfm?etdID=114.

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10

Han, Li. "G protein coupled receptor signaling to phospholipase D1 mediated by G12 type G proteins, LIM kinase and cofilin." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=968929923.

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11

Clyde-Smith, Jodi. "Characterization of ras isoform activation by ras guanine nucleotide exchange factors /." St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16393.pdf.

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12

Tsie, Marlene S. "Cloning and Immunolocalization of G Proteins in the Spionid Polychaete Dipolydora quadrilobata." Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/TsieMS2006.pdf.

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13

Yang, Zhao 1970. "Identification of a novel anti-apoptotic protein and characterization of mammalian regulators of G protein signaling (RGSs) in yeast." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=111875.

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Regulators of G protein signaling (RGSs) are negative regulators of G protein coupled receptors (GPCRs). Our lab has demonstrated that yeast Saccharomyces cerevisiae is a useful system to study RGS and G protein signaling. Mammalian RGSs can be expressed in yeast and favored to interact with mammalian GPCRs as well.
Based on the observation that human RGS1 causes yeast cell growth arrest, I therefore used RGS1 expressing yeast cells to screen a mouse T cell cDNA library in order to find potential interacting proteins. From the screen, I identified a mouse sphingomyelin synthase 1 (SMS1) cDNA. By using a series of different apoptotic stimuli, such as hydrogen peroxide, osmotic stress, exogenous ceramide and its precursors, high temperature etc., SMS1 expression was found to suppress cell growth arrest and prevent viability decline, indicating that SMS1 represents an anti-apoptotic protein that functions by decreasing the intracellular level of pro-apoptotic ceramide.
Gene analysis further indicated that the SMS1 gene consists of 16 exons spread over a 256kb portion of mouse chromosome 19. It is alternatively spliced to produce 4 different transcripts (SMS1alpha1, SMS1alpha2, SMS1beta and SMS1gamma) and encode 3 different proteins (SMS1alpha, SMS1beta and SMS1gamma). Notably, I found that SMS1beta protein does not interfere with SMS1alpha anti-apoptotic function, although both of these two proteins contain the protein-protein interaction domain, sterile alpha motif (SAM), at their N-terminus.
I also carried out a study to examine GPCR-RGS interactions using the yeast expression system. Our lab had noticed that there was an extra RGS5 related protein that was detected by western blot analysis in the protein extracts prepared from yeast and HEK293 cells expressing RGS5. The size of the band was approximately 2 times the molecular weight of RGS5, indicating the possibility that RGS5 forms a dimer. To further examine this hypothesis, I, therefore, performed a series of experiments, included yeast 2 hybrid assays, to demonstrate that RGS5 does interact with itself. This is the first report that RGS can form a dimer. The implications for this finding are discussed in detail.

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14

Lo, Kin Ho. "Activation of signal transducer and activator of transcription 3 (STAT3) by G[alpha]16 and G[alpha]14 via a c-Src/JAK-and ERK-dependent mechanism /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?BICH%202004%20LO.

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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.
Includes bibliographical references (leaves 92-111). Also available in electronic version. Access restricted to campus users.

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15

Hill, Claire Louise. "The use of Schizosaccharomyces pombe to investigate reguator of G protein signalling proteins." Thesis, University of Warwick, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487827.

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16

Barclay, Elaine. "Characterisation of palmitoylation in alpha₂_A adrenoceptor and 5-HT₁_A serotonin receptor-G₀₁α G protein fusion proteins." Thesis, University of Glasgow, 2004. http://theses.gla.ac.uk/4998/.

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Palmitoylation variant GPCR-G protein fusion proteins were created between the porcine u2A-adrenoceptor or the human 5-HT1A-serotonin receptor and the pertussis toxin resistant, Cys35lIle, form of the rat Go1u protein. These palmitoylation-variant fusions were transiently expressed in HEK293T cells prior to analysis of the regulation of palmitoylation and the functional consequences of palmitoylation for both the GPCR and G protein parts of the fusions. When the regulation of palmitoylation was studied for u2A-adrenoceptor-GoluCys35IIle fusion proteins, dynamic palmitoylation and depalmitoylation of both the Cys442residue of the u2A-adrenoceptor and the Cys ' residue of the GoluCys351Ile protein were found to occur. However, only the GOluCys351Ileprotein part of the fusion was found to undergo adrenaline-stimulated regulation of palmitoylation and the effect of adrenaline required G protein activation. Adrenaline regulation proceeded in a concentration-dependent manner correlating with agonist occupancy of the u2A-adrenoceptor. Such agonist effects were found to be, at least in part, due to agonist-stimulation of GOluCys351Ile protein depalmitoylation. The requirements for palmitoylation of the u2A-adrenoceptor and GoluCys351Ile protein elements of the u2A-adrenoceptor-GoluCys35IUe fusion proteins were subsequently assessed for various functional properties. Palmitoylation of neither the U2Aadrenoceptor nor the GoluCys351Ile protein parts of the fusion determined fusion protein expression levels, affinity for the agonist adrenaline, affinity for the antagonist RS- 79948-197, ability to bind or to hydrolyse GTP or their ability to influence the efficiency of RGS 16 protein to accelerate the GTPase reaction. In regulation of palmitoylation studies for 5-HTIA-receptor-GoluCys35IIle fusion proteins, dynamic palmitoylation of the Cys' residue of the GoluCys351Ue protein and the Cys417 residue of the 5-HTIA-receptor was observed as well as a lack of incorporation of palmitate into Cys420 of the 5-HT1A-receptor. Dynamic depalmitoylation was only observed for the Cys' residue of the GoluCys351Ile protein, not for the 5-HT1A-receptor. In the latter case, palmitate once incorporated appeared to remain stably attached. Both the 5-HT1A-receptor and the GoluCys351Ile protein parts of the fusion were found to undergo 8-0H-DPAT-stimulated regulation ofpalmitoylation. 8-0H-DPAT was able to regulate palmitoylation levels of both proteins in a concentration-dependent manner. For the regulation of GoluCys351Ile protein palmitoylation such agonist effects were found likely to be, at least in part, due to an agonist-stimulated rate of depalmitoylation. For the regulation of 5-HT1A-receptor palmitoylation such agonist-stimulated increases in observed palmitoylation levels were only attributable to the addition of palmitate, given that no depalmitoylation of the 5- HT1A-receptor could be detected. The requirements for palmitoylation of the 5-HT1A-receptor and GoluCys351Ile protein elements of the 5-HT1A-receptor-GoluCys351Ile fusion proteins were also assessed for a selection of functional properties. Similar to the results obtained with Go1uCys351Ile protein constrained to the uZA-adrenoceptor, the palmitoylation of the GoluCys351Ile protein did not determine fusion protein expression levels, their affinity for the antagonist WAYI00635, or their ability to bind GTP. Palmitoylation of 5-HT1Areceptor did not alter fusion protein expression levels or their affinity for the antagonist WAYI00635. However, in contrast, it did cause enhanced levels of GTP binding to the 5-HT1A-receptor-GoluCys351Ile fusion proteins. The results of this investigation suggest that there are different requirements for regulation of GPCR and G protein palmitoylation dependent on the GPCR-G protein fusion in question. These requirements may be responsible for the specific functional properties displayed by such fusions. The current study also demonstrates that GPCR-G protein fusion proteins can be successfully used as tools to study both the regulation of palmitoylation and the functional consequences of this modification.

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17

Slessareva, Janna Eugenievna. "Molecular mechanisms of G protein-receptor coupling." Morgantown, W. Va. : [West Virginia University Libraries], 2003. http://etd.wvu.edu/templates/showETD.cfm?recnum=2907.

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Thesis (Ph. D.)--West Virginia University, 2003.
Title from document title page. Document formatted into pages; contains vi, 200 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

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18

Ma, Hongzheng. "Molecular mechanisms of G protein-receptor coupling." Morgantown, W. Va. : [West Virginia University Libraries], 2003. http://etd.wvu.edu/templates/showETD.cfm?recnum=2978.

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Thesis (Ph. D.)--West Virginia University, 2003.
Title from document title page. Document formatted into pages; contains viii, 264 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

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19

Armenta, Blanco Jenny Marcela. "Capillary Electrophoresis of Proteins with Selective On-line Affinity Monoliths." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1594.pdf.

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20

Runne, Caitlin M. "Function and Activation Mechanism of PLEKHG2, A Novel G Beta Gamma-Activated RhoGEF in Leukemia Cells." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/4907.

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The Rho family of GTPases plays a crucial role in the regulation of diverse cellular processes, including proliferation and actin cytoskeletal rearrangement to promote cell migration. However, dysregulation of RhoGTPases has been associated with disease, particularly cancers such as leukemia. Despite this, RhoGTPases are rarely mutated in cancer. Rather, dysregulation of their regulatory proteins through mutation or overexpression contributes to disease pathogenesis. RhoGTPases are activated through Rho guanine nucleotide exchange factors (GEFs). Although over eighty RhoGEFs have been identified that activate the 25 RhoGTPases, the pathological role of the majority of these proteins remains unclear. Further, whereas the majority of RhoGEFs are activated through tyrosine phosphorylation, a small subset can be activated through heterotrimeric G proteins, including through GΒ;Γ; subunits. However, the mechanism by which GΒ;Γ; induces RhoGEF activation remains unclear. PLEKHG2 is a Dbl family RhoGEF that was originally identified as a gene upregulated in a leukemia mouse model, and later shown to be activated by heterotrimeric G protein Β;Γ; subunits. However, its function and activation mechanisms remain elusive. Here we show that, as compared to primary human T cells, the expression of PLEKHG2 is upregulated in leukemia cell lines. Downregulation of PLEKHG2 by siRNAs specifically inhibited GΒ;Γ;-stimulated Rac and Cdc42, but not RhoA activation. Consequently, inhibition of PLEKHG2 blocked actin polymerization, protrusion formation, and leukemia cell migration in response to SDF1alpha;. Additional studies indicate that GΒ;Γ; likely activates PLEKHG2 by binding the N-terminus of PLEKHG2. This interaction results in the release of autoinhibition imposed by the C-terminus within a region encompassing the catalytic DH domain. As a result, overexpressing either the N-terminus of PLEKHG2 that binds GΒ;Γ; or the C-terminus that autoinhibits PLEKHG2 blocked GΒ;Γ;-stimulated Rac and Cdc42 activation and the ability of leukemia cell to form membrane protrusions and to migrate. Together, our results have demonstrated that PLEKHG2 functions as a novel GΒ;Γ; -stimulated RhoGEF that could contribute to chemokine-induced leukemia cell dissemination and leukemia pathogenesis.

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21

Marcotte, Eric R. "G proteins and Parkinson's disease, the role of signal transducing G proteins in mediating dopamine receptor supersensitivity in Parkinson's disease." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0012/NQ42863.pdf.

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22

Zheng, Bin. "RGS proteins : bridging the "GAP"s between G protein signaling and membrane trafficking /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3059905.

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23

Terasmaa, Anton. "Dopamine D2 receptor G protein coupling and its regulation /." Stockholm, 2003. http://diss.kib.ki.se/2004/91-7349-788-6/.

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24

Anderson, David John. "Heterotrimeric G proteins in plant signal transduction : characterisation of tobacco and arabidopsis G ̊subunits /." [St. Lucia, Qld.], 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16840.pdf.

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25

Legate, Kyle R. Andrews D. W. "Characterization of the beta-subunit of the mammalian SRP receptor and its role in assembly of the SRP receptor /." *McMaster only, 2003.

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26

Vasara, Tuija. "Functional analysis of the RHOIII and 14-3-3 proteins of Trichoderma reesei /." Espoo [Finland] : Technical Research Centre of Finland, 2002. http://www.vtt.fi/inf/pdf/publications/2002/P466.pdf.

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27

Ip, Koon-ching. "Role of G[alpha]-interacting protein (GAIP) in modulation of MAPK pathways /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?BICH%202008%20IP.

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28

Poon, Lydia See Wing. "Molecular basis of G[beta][gamma] signaling : dimer formation and interaction with effectors and G[alpha] subunits /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?BICH%202009%20POON.

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29

Bane, Steven Edward. "Expression and characterization of the human neurokinin 1 receptor from Escherichia coli." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 99 p, 2007. http://proquest.umi.com/pqdweb?did=1342742951&sid=1&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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30

Krishnan, Kadalmani. "Characterisation of the G protein controlled tyrosine kinase, ACK1 and its interaction with nucleolar partner proteins." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610698.

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31

Mitchell, Christopher J. "The regulation of polyphosphoinositide synthesis in rat liver." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389879.

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32

Srivastava, Deepak Prakash. "Characterisation of a novel Drosophila G-protein coupled receptor differentially activated by catecholamines and steroids." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614677.

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Damoulakis, George. "The role of RhoG in neutrophil biology." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610225.

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Ferreira, Cláudia Susana da Rosa. "Organelle-specific roles for the Arf-like G proteins Arl5 and Arl8." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609430.

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35

Chan, Pui Wai. "Fhit : a novel interacting partner of G[alpha][subscript q] proteins /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?BICH%202008%20CHAN.

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36

Humphrey, Tania Vivienne. "Characterisation of a putative G-protein coupled receptor and its protein interacting partner in Arabidopsis /." St. Lucia, Qld, 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16260.pdf.

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Bailey, Laura Kate. "Structural and biochemical studies of small G protein effectors." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608914.

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38

McLeman, Elizabeth Rae. "Brain G-proteins in drug dependence, a postmortem study." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0001/MQ45410.pdf.

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39

Lupi, Rosita. "Characterization of post translational modification of heterotrimeric G proteins." Thesis, Open University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343748.

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40

Stanley, R. J. "Mathematical models of signalling through G proteins and phospholipids." Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1472846/.

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G proteins and phospholipids are two major classes of signalling molecule. ey are each-independently and together-involved in diverse 'signalling pathways' - bio- chemical networks through which cells maintain healthy responses to stimuli. A unique 'cross-talk motif' is formed by regulation of the phospholipid-modifying enzymes phospholipase D (PLD) and phosphatidylinositol 4-phosphate 5-kinase (PI4P5K) by the Arf family of small G proteins and-curiously-each other's product. Here, understanding of this inherently complex motif has been strengthened by the development and analysis of mathematical models, specifically systems of ordinary differential equations (ODEs). Construction of simple empirical models suggests asymmetry in the mechanisms of regulation of the enzymes is responsible for production of two distinct outgoing signals from a single input signal, one displaying threshold activation behaviour. Additionally, well-defined quasi-steady-state (QSS) mechanistic models (à la Michaelis- Menten) have been developed for each of: PLD; PI4P5K; and G protein/Arf regula- tion. During this process-due to insufficient pre-existing descriptions-biochemically- plausible assumptions were required for certain regulatory and catalytic interactions. Analysis of the G protein regulation models establishes that-contrary to previous representations-this regulation is best described by a balance/unbalance mechanism, where observed activation absolutely requires the presence of the inactivator. Together, the QSS models can be combined to form a complete model of the Arf/PLD/ PI4P5K motif suitable for computational simulation - preliminary parameters show that this model is capable of displaying physiologically-plausible behaviours ese results give a be er understanding of the signalling role of the Arf/PLD/PI4P5K motif; lead to novel biological hypotheses amenable to later experimental validation; highlight where our current biological understanding of the system is insufficient; and suggest novel methods for the therapeutic control of G proteins.

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41

Coleman, Struan Howard. "The regulation of the rpmB,G operon of Escherichia coli." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260156.

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42

Moon, Hyo-Eun. "Differential G protein activation by fusion proteins between the human #delta#-opioid receptor and Gâ†iâ‚Î±/Gâ†oâ‚Î± proteins." Thesis, University of Glasgow, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366183.

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43

Murphy, Jonathan Paul. "The cloning, expression, and characterisation of Streptoccal protein G." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316402.

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44

Wu, Hoi Ti. "Regulation of the pro-survival AKT signaling cascade : roles of receptor tyrosine kinases, G proteins, and their crosstalks /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?BICH%202006%20WU.

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45

Lai, Chun Wan Jeffrey. "Mechanism of G Protein Beta-Gamma Assembly Mediated by Phosducin-Like Protein 1." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/3190.

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G-protein coupled receptor signaling (GPCR) is essential for regulating a large variety of hormonal, sensory and neuronal processes in eukaryotic cells. Because the regulation of these physiological responses is critical, GPCR signaling pathways are carefully controlled at different levels within the cascade. Phosducin-like protein 1 (PhLP1) can bind the G protein βγ dimer and participate in GPCR signaling. Recent evidence has supported the concept that PhLP1 can serve as a co-chaperone of the eukaryotic cytosolic chaperonin complex CCT/TRiC to mediate G βγ assembly. Although a general mechanism of PhLP1-mediated G βγ assembly has been postulated, many of the details about this process are still missing. Structural analysis of key complexes that are important intermediates in the G βγ assembly process can generate snapshots that provide molecular details of the mechanism beyond current understanding. We have isolated two important intermediates in the assembly process, the Gβ1-CCT and PhLP1-Gβ1-CCT complexes assembled in vivo in insect cells, and have determined their structures by cryo-electron microscopy (cryo-EM). Structural analysis reveals that Gβ1, representing the WD40 repeat proteins which are a major class of CCT substrates, interacts specifically with the apical domain of CCTβ. Gβ1 binding experiments with several chimeric CCT subunits confirm a strong interaction of Gβ1 with CCTβ and map Gβ1 binding to α-Helix 9 and the loop between β-strands 6 and 7. These regions are part of a hydrophobic surface of the CCTβ apical domain facing the chaperonin cavity. Docking the Gβ molecule into the two 3D reconstructions (Gβ1-CCT and PhLP1-Gβ1-CCT) reveals that upon PhLP1 binding to Gβ1-CCT, the quasi-folded Gβ molecule is constricted to a more native state and shifted to an angle that can lead to the release of folded Gβ1 from CCT. Moreover, mutagenesis of the CCTβ subunit suggests that PhLP1 can interact with the tip of the apical domain of CCTβ subunit at residue S260, which is a downstream phosphorylation target site of RSK and S6K kinases from the Ras-MAPK and mTOR pathways. These results reveal a novel mechanism of PhLP1-mediated Gβ folding and its release from CCT. The next important step in testing the PhLP1-mediated Gβγ assembly hypothesis is to investigate the function of PhLP1 in vivo. We have prepared a rod-specific PhLP1 conditional knockout mouse in which the physiological consequences of the loss of PhLP1 functions have been characterized. The loss of PhLP1 has led to profound consequences on the ability of these rods to detect light as a result of a significant reduction in the expression of transducin (Gt) subunits. Expression of other G protein subunits as well as Gβ5-RGS9-1 complexes was also greatly decreased, yet all of this occurs without resulting in rapid degeneration of the photoreceptor cells. These results show for the first time the essential nature of PhLP1 for Gβγ and Gβ5-RGS dimer assembly in vivo, confirming results from cell culture and structural studies.

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46

Venkatakrishnan, Aiveliagaram Jayagopal. "Understanding the principles of structural organisation of G-protein-coupled receptors." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648272.

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47

García-Jiménez, Angela. "G-proteins and adenylyl cyclase in Alzheimer's disease postmortem brain /." Stockholm : [Karolinska institutets bibl.], 2002. http://diss.kib.ki.se/2002/91-7349-103-9.

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48

Onel, Buket, and Buket Onel. "Promoter G-quadruplexes and their Interactions with Ligands and Proteins." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/621857.

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G-quadruplex secondary structures are four-stranded globular nucleic acid structures that form in specific DNA and RNA G-rich sequences with biological significance, such as those found in human telomeres, oncogene promoter regions, replication initiation sites, and 5’- and 3’-untranslated (UTR) regions, which have been identified as novel drug targets. The non-canonical G-quadruplex secondary structures readily form under physiologically relevant ionic conditions, and exhibit great diversity in their topologies and loop conformations depending on the DNA or RNA sequences at hand. The structural diversity of these unique secondary structures is essential to their specific recognition by different regulatory proteins or small molecule compounds. A significant amount of research has been done in this field that provides compelling evidence for the existence, biological significance, and potential druggability of G-quadruplexes. In this dissertation, I explore G-quadruplex formation in the promoters of BCL2, PDGFR-β and c-Myc oncogenes and their interactions with small molecule compounds or proteins. Firstly, I investigated a newly-identified G-quadruplex (P1G4) forming immediately upstream of the human BCL2 gene, which has been found to be overexpressed in several human tumors. In this research, I have found that P1G4 acts as a transcription repressor, and that its inhibitory effect can be enriched by the G-quadruplex-interactive compound, TMPyP4. Both P1G4 and the previously reported Pu39 G-quadruplexes form independently in adjacent regions within the BCL2 P1 promoter, but P1G4 appears to play a more dominant role in repressing transcriptional activity. NMR and CD studies have shown that the P1G4 G-quadruplex appears to comprise a novel dynamic equilibrium of two parallel structures, one regular, with two 1-nt loops and a 12-nt middle loop, and another broken-stranded, with three 1-nt loops and an 11-nt middle loop; both structures adopt a novel hairpin (stem-loop duplex) conformation in the long central loop. This dynamic equilibrium of two closely-related G-quadruplex structures with a unique hairpin loop conformation may provide a specific target for small molecules to modulate BCL2 gene transcription. I also explored the 3’ end G-quadruplex that forms within the core promoter of PDGFR-β, which has also been observed to be present at abnormal levels in a variety of clinical pathologies, including malignancies. The 3′-end G-quadruplex formed in the PDGFR-β promoter NHE appears to be selectively stabilized by an ellipticine analog, GSA1129, which can shift the dynamic equilibrium in the full-length sequence to favor the 3′-end G-quadruplex, and can repress PDGFR-β activity in cancer cell lines. NMR studies in combination with biophysical experiments have shown that in the wild-type extended 3ʼ-end NHE sequences, two novel intramolecular G-quadruplexes can be formed in a potassium solution, one with a 3’-flanking distant guanine inserted into the 3’-external tetrad (3’-insertion G-quadruplex), and another with a 5’-flanking distant guanine inserted into the 5’-external tetrad (5’-insertion G-quadruplex). Further investigation of the elongated PDGFR-β 3′-end sequence containing both the 5’- and 3’- flanking guanine sequences showed the formation of a combination of the two G-quadruplexes existing in equilibrium. Importantly, it was observed that GSA1129 can bind to and increase the stability of each of the end-insertion G-quadruplexes, raising their Tₘ by 25 degrees. This study highlights the dynamic nature of the 3′-end NHE sequence and the importance of identifying the proper sequence for the formation of biologically relevant G-quadruplex structures. Significantly, the dynamic nature of the 3′-end G-quadruplex suggests that it may be an attractive target for drug regulation. I then analyzed two proteins, Nucleolin and NM23-H2, which interact with the c-Myc G-quadruplex structure that forms in the proximal promoter region of the c-Myc gene; this is one of the most commonly deregulated genes in the human neoplasm. Nucleolin is known to be a transcriptional repressor for c-Myc, binding to and stabilizing the c-Myc G-quadruplex, whereas NM23-H2 is known to be a transcriptional activator that unwinds and destabilizes the c-Myc G-quadruplex. An investigation of the molecular mechanisms of the interaction between the c-Myc G-quadruplex and nucleolin showed that the minimal binding domains required for a tight binding of the protein to the c-Myc G-quadruplex are the four RNA binding domains (RBDs) of nucleolin, referred to as Nuc1234, and that the RGG domain is unnecessary for c-Myc G-quadruplex binding. The stable G-quadruplex formed within Pu27 using G-tract runs I, II, IV and V was determined to be the best substrate (Myc1245T) for nucleolin binding, showing the highest affinity. 3D NMR experiments performed on the free protein Nuc1234 and its complex with the Myc1245T G-quadruplex have shown that upon complex formation, only the disordered linker regions of the protein display significant chemical shift changes, whereas most other residues show chemical shift values similar to those of the free protein. The c-Myc G-quadruplex has three loops that flip outward in a solvent containing K⁺, according to its structure. The hypothesis for this association is that nucleolin wraps around the G-quadruplex and interacts specifically with the flipped-outward loop regions of the c-Myc G-quadruplex via its own inter-RBD linker regions, with little structural change in the RBDs themselves. A definitive determination of the 3D molecular structure of nucleolin and its complex with Myc1245T is currently in development. Biophysical and structural studies were then conducted to investigate the interactions of the protein NM23-H2/NDP kinase B with the c-Myc G-quadruplex. NM23-H2 binds to single-stranded guanine- and cytosine-rich sequences, but not to double-stranded DNA in the NHE III₁ region; the binding therefore appears structure-specific, rather than sequence-specific. Moreover, increasing concentrations of the strong G-quadruplex-interactive compound TMPyP4, a porphyrin-based drug, inhibits the binding of NM23-H2 to the NHE III₁ region; this suggests that the stabilization of the G-quadruplex hinders the recognition and remodeling function of the NM23-H2. By conducting Forster Resonance Energy Transfer (FRET) assays in combination with Circular Dichroism (CD) studies, I demonstrated that NM23-H2 can actively resolve the c-Myc G-quadruplex. Taken together, these results show that the use of small molecules to prevent NM23-H2 from binding to and resolving the NHE III₁ region G-quadruplex may have the potential to inhibit c-Myc transcription for cancer therapeutic purposes. This underlines the importance of understanding the mechanism of function operating between NM23-H2 and the c-Myc G-quadruplex. Understanding molecular mechanism between NM23-H2 and c-Myc is under investigation.

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49

Woon, Chee-Wai. "Mutations of the Alpha-Subunit of G-Proteins: A Thesis." eScholarship@UMMS, 1988. http://escholarship.umassmed.edu/gsbs_diss/296.

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Signal transduction by G-proteins (a heterotrimer membrane protein composed of an α, β, and γ subunit) requires that the α-subunit undergoes a transition from a GDP-bound inactive state to an activated GTP-bound state. The exchange of GDP for GTP leads to a conformational change in the α-subunit that results in the loss of affinity for the βγ subunits. We predicted that appropriate genetic manipulation of key regions of the α-subunit could result in the induction of the active conformation that would mimic at least in part the activated GTP-bound state. We have demonstrated that the substitution of the 38 amino acid residue carboxyl termimus of Gαs with the last 36 amino acid residues of Gαi2 resulted in a chimeric Gα-subunit (C4) that exhibits a constitutively active Gαs-like activity. Similarly, the substitution of the amino terminal 61 amino acid residues of Gαs with the first 54 residues of Gαi2 also resulted in a chimeric Gα-subunit that is persistently active (Gs like). We have also generated point mutations in the Gαs subunit that are comparable to the activating mutations in the ras protein. Our results suggest that point mutations in the signature sequence of the A (Val 49) and C (Thr 225) homologous regions that are implicated in regulating the GTPase activity of the molecule also resulted in the activation of the subunit. The present study has identified four key regions of the α-subunit that are critical for the activity and regulation of the Gs protein.

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Casteel, Darren E. "Identification and characterization of G-Kinase I[beta] interacting proteins /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2003. http://wwwlib.umi.com/cr/ucsd/fullcit?p3099538.

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