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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
661

Infrastruktur och miljöpåverkan från tunga transporter vid ett slutförvar av kärnavfall i Oskarshamns kommun

Nilsson, Anneli January 2008 (has links)
<p>Denna rapport utreder översiktligt regional och kommunal infrastruktur ochmiljöpåverkan från transporter av bergmassor, bentonit och lera vid ett slutförvar avkärnavfall eller om det inte blir ett slutförvar i Oskarshamns kommun. Strategin harvarit att utefter de regionala miljökvalitetsmålen begränsad klimatpåverkan, frisk luftsamt det länsegna målet fossilbränslefri zon år 2030 undersöka hur olika lastbärare(lastbil, tåg och fartyg) bidrar till måluppfyllelse. Slutsatsen är att det mest troligascenariot med transporterna är olika transportalternativ beroende på vart materialetskall någonstans och vad det skall användas till. Oavsett om det blir ett slutförvar ellerej i Oskarshamns kommun, kommer infrastrukturen att bli förändrad, speciellt för deboende i Misterhults socken. Fossilbränslefrizon år 2030 är det målet som inte skullenå måluppfyllelse ifall enbart lastbärare med fossilt bränsle skulle användas vidtransporterna.</p><p>2008:Nr 3 Teknik</p>
662

Acides aminés et cancer : LAT1, un transporteur essentiel à l’activité mTORC1 et la croissance tumorale / Amino acids and cancer : LAT1, a transporter essential for mTORC1 activity and tumor growth

Cormerais, Yann 22 July 2016 (has links)
Dans le but de maintenir leur métabolisme et leur prolifération exacerbée, les tumeurs sont dépendantes d’un apport accru en acides aminés. Afin d'optimiser cet apport, les tumeurs surexpriment certains transporteurs clés tels que l'hétérodimère multifonctionnel CD98/LAT1. CD98 (SLC3A2) agit comme co-récepteur des intégrines β et amplifie leur signalisation régulant ainsi la migration et l'adhésion cellulaire. La protéine LAT1 (SLC7A5) est quant à elle responsable du transport des acides aminés (AA) essentiels. Des études antérieures ont suggéré que la fonction CD98/intégrines du complexe est essentielle à la croissance tumorale, alors que LAT1 aurait un rôle mineur dans ce contexte. Cependant, les besoins nutritifs accrus des cellules tumorales nous ont conduit à émettre l’hypothèse contraire selon laquelle l’avantage prolifératif donné par ce complexe serait en réalité supporté par l’activité du transporteur LAT1 et non pas par l’interaction CD98/intégrine. Dans ce contexte, j’ai montré que l’invalidation génétique ou pharmacologique de LAT1 dans différentes lignées tumorales entraine une suppression totale du transport de la leucine, sodium-indépendant. Ceci entrainant une perte d’homéostasie des AA avec l’activation de la voie de stress GCN2, l’inhibition de mTORC1 et la suppression de la croissance tumorale. De plus, l’invalidation génétique de CD98 ne s’est traduite par aucun phénotype visible. Cependant, la suppression de l'activité résiduelle de LAT1 de ces cellules est suffisante pour abolir leur potentiel tumoral. Ainsi, mes résultats démontrent le rôle clé de LAT1 dans la croissance tumorale en faisant ainsi une cible thérapeutique prometteuse. / Tumours rely on external amino acids (AA) uptake to maintain their exacerbated metabolism and proliferation. To optimize AA uptake, tumors overexpress key carriers such as the multifunctional CD98/LAT 1 heterodimer. CD98 (SLC3A2) acts as a co-receptor of β integrins and enhances signaling that promotes cellular migration and invasion. LAT1 (SLC7A5) is responsible for the transport of essential AA. Previous studies have suggested that the CD98/integrin axis of the complex is essential for tumour growth, while LAT1 activity is dispensible. However, the increased nutritional requirements of tumor cells led us to hypothesize that the proliferative advantage given by this complex is in fact supported by the AA transporter activity of LAT1 and not by the CD98/integrin activity. In this context, I have shown that genetic or pharmacological invalidation of LAT1 in various tumor cell lines leads to a complete removal of the sodium-independent leucine transport. This leads to a loss of AA homeostasis with activation of the GCN2 stress pathway, inhibition of mTORC1 and supression of tumour growth. In addition, genetic invalidation of CD98 did not result in any detectable phenotype. However, inhibition of the residual activity of LAT1 in CD98 knockout cells is sufficient to abolish their tumorigenicity. Thus, my results clearly demonstrate the fundamental role of LAT1 in tumour growth and advocate the pharmacology development of LAT1 transporter inhibitors as very promising anticancer agents.
663

Inhibition of Aryl Hydrocarbon Receptor (AhR) Activity Decreases ABCG2 Expression and Activity

Williams, Stanley J 21 May 2018 (has links)
The androgen receptor’s (AR) resurgence following treatment leads to castration resistant prostate cancer (CRPC). Studies show that the aryl hydrocarbon receptor (AhR) regulates AR signaling, is constitutively active, and enhances AR signaling in CRPC. AhR has ligands with carcinogenic properties and interacts with phytochemicals with anti-tumorigenic properties. Curcumin inhibits AhR activity and multidrug transporter ABCG2 activity, which mediates substrates out of the cell. Elevated ABCG2 expression causes resistance to anticancer drugs. AhR transcriptionally activates ABCG2 and our hypothesis is that inhibition of AhR activity by curcumin will decrease ABCG2 expression and activity in CRPC cells. C4-2 cells were treated with increasing concentrations of curcumin (0, 10, 25, 50µM) and CH223191 (50µM). Results show that curcumin decreases AhR, CYP1B1 and ABCG2 gene expression. Higher concentrations of curcumin diminish AhR and ABCG2 protein expression, ABCG2 activity, and cell proliferation. These results will help reveal a role for AhR in drug resistance.
664

How Does ATP Regulate Erythrocyte Glucose Transport?: a Dissertation

Leitch, Jeffry M. 05 June 2007 (has links)
Human erythrocyte glucose sugar transport displays a complexity that is not explained by available models. Sugar transport was examined in resealed red cell ghosts under equilibrium exchange conditions (intracellular [sugar] = extracellular [sugar]). Exchange 3-O-methylglucose (3MG) import and export are monophasic in the absence of cytoplasmic ATP but are biphasic when ATP is present. Biphasic exchange is observed as the rapid filling of a large compartment (66% cell volume) followed by the slow filling of the remaining cytoplasmic space. Two models for biphasic sugar transport are presented in which 3MG must overcome a sugar-specific, physical (diffusional) or chemical (anomerization) barrier to equilibrate with cell water. The anomerization model was rejected through several lines of direct experimental investigation. 1) The sizes of the fast and slow phases of sugar transport do not correlate with the equilibrium anomer distributions of all GLUT1 sugar substrates. 2) Increasing the rate of anomerization by addition of exogenous intracellular mutarotase has no effect on biphasic transport kinetics. 3) Direct measurement of initial rates of sugar uptake or exchange demonstrates that GLUT1 shows no anomer preference. The physical barrier model was further refined by the use of the counterflow condition (intracellular [sugar] >> extracellular [sugar]). The presence of a physical barrier alone was unable to explain the complex counterflow time courses observed. As a result, the model was modified to include the action of a specific sugar export that is compartmentalized from rapidly equilibrating, GLUT1-mediated uptake and exit.
665

Expressão gênica em complexos cumulus-oócito bovinos selecionados pela atividade da glicose-6-fosfato desidrogenase / Genetic expression in bovine cumulus oocyte complexes selected by activity of glucose-6-phosphate dehydrogenase

Lopes, Eliana Franco January 2013 (has links)
O objetivo desse trabalho foi avaliar a expressão de genes envolvidos no transporte de monocarboxilatos (Mct1, Mct2, Mct3 e Mct4) e de genes específicos da oogênese (Bmp15, Gdf9 e Has2) em complexos cumulus-oócito (CCOs) selecionados pelo teste BCB. Após seleção morfológica com base no grau de compactação das células do cumulus (CCs) e no grau de homogeneidade do citoplasma, os CCOs foram corados com 26 μM BCB (azul cresil brilhante) por 90 min e divididos em dois grupos: BCB+, que apresentavam o ooplasma corado de azul, e BCB-, com ooplasma não corado. Foram utilizados dois grupos controles não expostos ao BCB: o grupo holding foi submetido às mesmas condições que os grupos corados e o outro grupo controle foi diretamente submetido à maturação in vitro (MIV), após a seleção morfológica dos CCOs. A expressão gênica relativa foi determinada por RT-PCR em CCOs coletados antes e ao final da maturação. A expressão também foi avaliada, separadamente, em oócitos desnudos (ODs) e células do cumulus (CCs) antes e após a maturação. A análise dos transcritos demonstrou que houve aumento significativo (p < 0,05) na expressão relativa de Gdf9 e Bmp15 nos grupos BCB+, BCB- e holding antes da MIV, enquanto Has2 teve aumento significativo (p < 0,01) após a MIV apenas no grupo controle. Os outros genes analisados (Mct1, Mct2 e Mct4) mantiveram-se estáveis durante a maturação. O aumento na abundância relativa de alguns transcritos durante a MIV pode ser atribuído as condições de incubações durante o teste BCB. Nossos resultados demonstraram, pela primeira vez, a expressão de Mct1, 2 e 4 em CCOs bovinos. Enquanto o mRNA de Mct1 e Mct4 estava presente em ODs e em CC, o Mct2 foi detectado somente em CCs. Não detectamos a expressão de transcritos de Mct3 em CCOs. As diferenças na expressão dessas três isoformas sugerem um papel único para esses transportadores durante a maturação. / The aim of this study was to determine the relative expression of genes involved in transport of monocarboxylates (Mct1, Mct2, Mct3 e Mct4) and oogenesis specific genes (Bmp15, Gdf9 and Has2) in immature and mature bovine cumulus-oocyte complexes (COC) after selection by BCB. Immature COCs underwent morphological selection and were stained with 26 mM BCB for 90 min. Based on ooplasm staining, oocytes were distributed in two groups BCB+ (blue color) and BCB- (non-stained). The holding control group was exposed to the same incubation conditions as stained COCs, but without BCB. Control group was submitted to in vitro maturation (IVM) immediately after morphological selection. mRNA expression was investigated by RT-PCR in COCs before and after IVM. No relationship was observed in the relative expression of Has2, Gdf9, Bmp15 or Mct1, 2 and 4 transcripts between BCB- and BCB+ COCs. Transcripts analysis showed that Gdf9 and Bmp15 in BCB+, BCB- and holding groups were upregulated (p < 0.05) before IVM, while Has2 was up-regulated (p < 0.01) after IVM in the control group. Others genes remained stable during maturation (Mct1, 2 and 4). The increase in relative abundance of some transcripts during IVM may be attributed to incubation conditions during the BCB test. Our results showed, for the first time, Mct1, 2 and 4 expression in bovine COCs. Mct1 and Mct4 transcripts were present in denuded oocytes and cumulus cell, while Mct2 was detected only in cumulus cells. These differences between the three isoforms in localization suggest unique roles for each in monocarboxylate transport during maturation.
666

Avaliação da Densidade do Transportador Dopaminérgico utilizando [99MTc]-TRODAT-1 E SPECT em pacientes com movimentos periódicos das pernas após teste de esforço máximo

Cavagnolli, Daniel Alves [UNIFESP] 26 January 2011 (has links) (PDF)
Made available in DSpace on 2015-07-22T20:49:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-01-26 / Objetivo: O objetivo do presente estudo foi avaliar o perfil da densidade do transportador dopaminérgico utilizando SPECT em pacientes com Movimento Periódico das Pernas (MPP) e a influência do exercício físico agudo na concentração do DAT após um teste de esforço máximo (TEM). Métodos: Para isso 16 pacientes (8 grupo CTRL e 8 grupo Experimental) realizaram uma polissonografia (PSG) basal para a avaliação do padrão de sono e do índice do MPP. Após a PSG basal foi realizado o SPECT basal. Posteriormente os voluntários realizaram um TEM no período da manhã, após 2 horas, um novo exame de SPECT, e na mesma noite uma PSG para avaliar o efeito do exercício físico agudo no DAT e no padrão do sono. Resultados: Os resultados encontrados demonstraram que o grupo experimental apresentou valores menores no perfil da densidade do DAT no momento basal na região do estriado (p=0,03), foi demonstrado também uma redução do índice de MPP no grupo experimental (p=0,01) e um aumento da porcentagem do estagio 1 do sono NREM em ambos os grupos após o TEM (p=0,02). O estagio 2 do sono (p=0,02) e sono de ondas lentas (p=0,01) apresentaram diferenças entre os grupos no momento basal. Conclusão: Nossos resultados mostram que pacientes com MPP apresentaram uma menor densidade de DAT na região do putâmen esquerdo comparado ao grupo CTRL e uma sessão de exercício físico agudo (TEM) não alterou este perfil. Esses achados sugerem que alterações na densidade do DAT, talvez estejam relacionados a prática de exercício físico crônico. / Restless legs syndrome and periodic leg movement are sleep-related movement disorders and studies have shown changes in striatal dopaminergic activity in patients with these disorders. Physical exercise has been shown to improve the symptoms of restless legs syndrome and periodic leg movement, as has treatment with dopamine agonists. However, the mechanism by which physical exercise acts as a nonpharmacological treatment in improving symptoms of restless legs syndrome and periodic leg movement remains unknown. We evaluated dopamine transporter density profiles in 16 sedentary patients (control and experimental - with periodic leg movement, groups) and the influence of acute physical exercise on its concentration after a maximal exercise test. Each patient underwent baseline polysomnography to evaluate sleep patterns and periodic leg movement index values. After obtaining the polysomnography baseline, the single photon emission computer tomography baseline was determined. Subsequently, the volunteers performed a maximal exercise test in the morning, followed by a single photon emission computer tomography two hours later and polysomnography that night, to assess the effect of acute physical exercise on dopamine transporter and sleep patterns. The results showed significant lower dopamine transporter baseline densities in the striatum region for the experimental group. The results also showed a significant reduction in the periodic leg movement rate in the experimental group and a significant increased percentage of stage-1 non-REM sleep in both groups after maximal exercise test. Significant differences between the groups were only observed for Stage 2 sleep and slow wave sleep. Our results show that patients with periodic leg movement had a lower dopamine transporter density in the left putamen region compared to the control group and an acute physical exercise (maximal exercise test) did not alter this profile, providing evidence that this improvement is the result of chronic physical exercise. / TEDE / BV UNIFESP: Teses e dissertações
667

Identificação e caracterização dos genes abcCl1 e cypCl1 que codificam um transportador ABC e um citocromo P450 no fitopatógeno Colletotrichum lindemuthianum / Identification and characterization of the genes abcCl1 and cypCl1 that codify an ABC transporter and a cytochrome P450 in phytopathogen Colletotrichum lindemuthianum

Oliveira, Maycon Campos 20 February 2009 (has links)
Made available in DSpace on 2015-03-26T13:51:45Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1393738 bytes, checksum: a972ec00e49dcfa2c5d44a8c6f9480a0 (MD5) Previous issue date: 2009-02-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The plants produce antifungous proteins and specialized antibiotics (phytoanticipins and phytoalexins) in order to defend from phytopathogenic fungus. Only the pathogens able to avoid those defensive plant responses at the initial stages of the infection are able to cause disease. The fungus Colletotrichum lindemuthianum (Sacc. & Magnus) Briosi & Cavara is the etiological agent of the anthracnose in the common bean plant (Phaseolus vulgaris L.), that is an important disease contributing to reduce the productivity of the bean plant crop in Brazil. The genes abcCl1 and cypCl1 were isolated from this phytopathogen and their deduced aminoacid sequences have high similarity with ABC transporters and cytochromes P450, respectively. Those genes are found in unique copy and clustered in genome of the fungus, as revealed by either the sequencing of one DNA 8,4 kb fragment from the genomic library of C. lindemuthianum and the hybridization profile. Those genes also show an increased expression in response to different toxic compounds, mainly when the fungus is grown at the presence of eugenol, hygromycin and pisatin phytoalexin. Therefore, besides their genes to be physically linked, the proteins ABCCl1 and CYPCl1 can also be involved in the same functional process: the fungus resistance to the toxic compounds produced by plants or antagonistic microorganisms. In the functional analysis of the gene abcCl1, the mutants abcCl1&#8722; showed reduction in their virulence to the leaf of the common bean plant, compared with the wild line of C. lindemuthianum. Those results indicate the gene abcCl1 to codify an ABC transporter that is necessary to pathogenicity of C. lindemuthianum, probably because providing the fungus with the ability to overcome the defense mechanism of the plant. The cytochrome P450, that is codified by the gene cypCl1, can represent a complementary detoxification mechanism used by this fungus during the establishment of the disease. / Para se defenderem de fungos fitopatogênicos, as plantas produzem proteínas antifúngicas e antibióticos especializados (fitoanticipinas e fitoalexinas). Somente patógenos que conseguem evitar estas respostas defensivas da planta nos estágios iniciais da infecção são capazes de causar doença. O fungo Colletotrichum lindemuthianum (Sacc. & Magnus) Briosi & Cavara é o agente etiológico da antracnose do feijoeiro comum (Phaseolus vulgaris L.), uma importante doença que contribui para redução da produtividade da cultura do feijoeiro no Brasil. Neste fitopatógeno foram isolados dois genes, abcCl1 e cypCl1, cujas sequências de aminoácidos deduzidas possuem alta similaridade com transportadores ABC e citocromos P450, respectivamente. Estes genes estão presentes em cópia única e agrupados no genoma do fungo, conforme revelado no sequenciamento de um fragmento de DNA de 8,4 kb da biblioteca genômica de C. lindemuthianum, bem como no perfil de hibridização. Estes genes também apresentam aumento de expressão em resposta a diferentes compostos tóxicos, principalmente quando o fungo é crescido na presença de eugenol, higromicina ou fitoalexina pisatina. Assim, além de seus genes estarem ligados fisicamente, as proteínas ABCCl1 e CYPCl1 podem, também, estarem envolvidas em um mesmo processo funcional: a resistência do fungo a compostos tóxicos produzidos por plantas ou microrganismos antagonistas. Na análise funcional do gene abcCl1, foi observado que mutantes abcCl1&#8722; apresentam redução na virulência a folhas de feijoeiro comum, em comparação com a linhagem selvagem de C. lindemuthianum. Estes resultados indicam que o gene abcCl1 codifica um transportador ABC, que é necessário para a patogenicidade de C. lindemuthianum, provavelmente por conferir ao fungo a capacidade de superar algum mecanismo de defesa da planta. O citocromo P450, codificado pelo gene cypCl1, pode representar um mecanismo complementar de destoxificação empregado por este fungo durante o estabelecimento da doença.
668

Expressão gênica em complexos cumulus-oócito bovinos selecionados pela atividade da glicose-6-fosfato desidrogenase / Genetic expression in bovine cumulus oocyte complexes selected by activity of glucose-6-phosphate dehydrogenase

Lopes, Eliana Franco January 2013 (has links)
O objetivo desse trabalho foi avaliar a expressão de genes envolvidos no transporte de monocarboxilatos (Mct1, Mct2, Mct3 e Mct4) e de genes específicos da oogênese (Bmp15, Gdf9 e Has2) em complexos cumulus-oócito (CCOs) selecionados pelo teste BCB. Após seleção morfológica com base no grau de compactação das células do cumulus (CCs) e no grau de homogeneidade do citoplasma, os CCOs foram corados com 26 μM BCB (azul cresil brilhante) por 90 min e divididos em dois grupos: BCB+, que apresentavam o ooplasma corado de azul, e BCB-, com ooplasma não corado. Foram utilizados dois grupos controles não expostos ao BCB: o grupo holding foi submetido às mesmas condições que os grupos corados e o outro grupo controle foi diretamente submetido à maturação in vitro (MIV), após a seleção morfológica dos CCOs. A expressão gênica relativa foi determinada por RT-PCR em CCOs coletados antes e ao final da maturação. A expressão também foi avaliada, separadamente, em oócitos desnudos (ODs) e células do cumulus (CCs) antes e após a maturação. A análise dos transcritos demonstrou que houve aumento significativo (p < 0,05) na expressão relativa de Gdf9 e Bmp15 nos grupos BCB+, BCB- e holding antes da MIV, enquanto Has2 teve aumento significativo (p < 0,01) após a MIV apenas no grupo controle. Os outros genes analisados (Mct1, Mct2 e Mct4) mantiveram-se estáveis durante a maturação. O aumento na abundância relativa de alguns transcritos durante a MIV pode ser atribuído as condições de incubações durante o teste BCB. Nossos resultados demonstraram, pela primeira vez, a expressão de Mct1, 2 e 4 em CCOs bovinos. Enquanto o mRNA de Mct1 e Mct4 estava presente em ODs e em CC, o Mct2 foi detectado somente em CCs. Não detectamos a expressão de transcritos de Mct3 em CCOs. As diferenças na expressão dessas três isoformas sugerem um papel único para esses transportadores durante a maturação. / The aim of this study was to determine the relative expression of genes involved in transport of monocarboxylates (Mct1, Mct2, Mct3 e Mct4) and oogenesis specific genes (Bmp15, Gdf9 and Has2) in immature and mature bovine cumulus-oocyte complexes (COC) after selection by BCB. Immature COCs underwent morphological selection and were stained with 26 mM BCB for 90 min. Based on ooplasm staining, oocytes were distributed in two groups BCB+ (blue color) and BCB- (non-stained). The holding control group was exposed to the same incubation conditions as stained COCs, but without BCB. Control group was submitted to in vitro maturation (IVM) immediately after morphological selection. mRNA expression was investigated by RT-PCR in COCs before and after IVM. No relationship was observed in the relative expression of Has2, Gdf9, Bmp15 or Mct1, 2 and 4 transcripts between BCB- and BCB+ COCs. Transcripts analysis showed that Gdf9 and Bmp15 in BCB+, BCB- and holding groups were upregulated (p < 0.05) before IVM, while Has2 was up-regulated (p < 0.01) after IVM in the control group. Others genes remained stable during maturation (Mct1, 2 and 4). The increase in relative abundance of some transcripts during IVM may be attributed to incubation conditions during the BCB test. Our results showed, for the first time, Mct1, 2 and 4 expression in bovine COCs. Mct1 and Mct4 transcripts were present in denuded oocytes and cumulus cell, while Mct2 was detected only in cumulus cells. These differences between the three isoforms in localization suggest unique roles for each in monocarboxylate transport during maturation.
669

Modulace centrální cholinergní neurotransmise. / Modulation of central cholinergic neurotransmission

Valušková, Paulína January 2017 (has links)
Introduction: Central cholinergic system plays a key role in control of different brain functions such as learning, memory, attention, locomotion and rewards. Disrupted integrity, regulation or capacity of cholinergic signalling is closely connected with cognitive symptoms of several neurodegenerative and neuropsychiatric diseases, as Alzheimer disease, Parkinson disease, attention deficit hyperactivity disorder (ADHD), depression, schizophrenia and increased distractibility. The major neurotransmitter of cholinergic neurons is acetylcholine (ACh) and regulation of ACh levels is main pharmacotherapeutic approach to the treatment of diseases associated with central cholinergic system. The aim of the thesis was to study the changes of central cholinergic neurotransmission with respect to various aspects of modulation of ACh levels in the brain by controlling its release through M4 muscarinic receptors (MR), its hydrolysis by acetylcholinesterase (AChE) or butyrylcholinesterase (BChE) and after hydrolysis in the synapse, regulation of the uptake of metabolite choline by high affinity choline transporter (CHT). Methods: Here we used telemetry to measure locomotor activity and body temperature in mice with selective deletion of M4 MR (M4KO) and their wild type (M4WT) controls under the basal conditions...
670

Études structurales et fonctionnelles de protéines impliquées dans l’assimilation du fer chez les bactéries Gram-négatives / Structural and functionnal studies of proteins involved in iron uptake in Gram-negative bacteria

Brillet, Karl 11 April 2013 (has links)
Le fer est un élément essentiel à la vie car il possède un rôle clé dans de nombreux processus biologiques.Malgré son abondance au niveau de la croûte terrestre, le fer est très faiblement biodisponible. Pour contourner ce problème, la majorité des micro-organismes a développé différents systèmes particulièrement efficaces pour l’acquisition de cet élément. Le mécanisme le plus répandu implique la production et la sécrétion de petites molécules chélatrices ayant une forte affinité pour le fer. Après sécrétion dans le milieu extracellulaire, ces composés chélatent le Fe3+ et le transportent ensuite au travers de la membrane externe via des transporteurs TonB-dépendants (TBDT). Durant cette thèse, nous avons mis en place un protocoleefficace permettant d’aller rapidement du clonage à la cristallisation de ces cibles afin d’étudier la structure tridimensionnelle de cette famille de protéines. Ainsi, nous avons pu résoudre et étudier la structure de plusieurs TBDT, de bactéries Gram-négatives. Ainsi nous avons mis en évidence un mouvement du domaine de signalisation en présence du ligand, proposé un mécanisme de transporteur de la molécule d’hème par le système shu chez Shigella dysenteriae. Chez les bactéries du genre Pseudomonas, nous avons élucidé et caractérisé au niveau structural les mystères de l’énantiosélectivité des pyochélines. En parallèle, nous nous sommes intéressé au devenir du ferri-sidérophore au niveau du périplasme, chez P. aeruginosa, ainsi qu’au transport du fer au travers de la membrane interne grâce à un transporteur ABC FpvCDEF ayant laparticularité de posséder deux protéines périplasmiques associées capables d’interagir avec le sidérophore. / Iron is essential for life because it has a key role in many biological processes. Despite its abundance in the earth's crust, iron is poorly bioavailable. To circumvent this problem, most micro-organisms have developed different systems particularly effective for the acquisition of this element. The most common mechanism involves the production and secretion of small chelating molecules having high affinity for iron. After secretion into the extracellular medium, these compounds chelate and transport ferric iron through the outer membrane via TonB-dependent transporters (TBDTs). In this thesis, we have developed an efficient protocol to easily go from cloning to crystallization of these targets and then studied the three-dimensional structure of this protein family. Thus, we were able to solve and study the structure of several TBDT of Gram-negative bacteria. We have identified a movement of the signaling domain in the presence of ligand. We proposed a mechanism for heme translocation through the shu system, in Shigella dysenteriae. In Pseudomonas species, we elucidated and characterized at the structural level the mysteries of the pyochelin enantioselectivity. In Pseudomonas aeruginosa, we studied the ferri-siderophore become in the periplasmic space, as well as iron transport across the inner membrane by an ABC transporter, named FpvCDEF, with the particularity of having two periplasmic proteins associated able to interact with the siderophore.

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