Membrane attachment of ephrin ligands plays an important role in Eph receptor activation. Membrane anchorage is thought to provide a clustering effect to ephrins that is necessary for stimulation of Eph receptor kinase activity. The presence of soluble A-type ephrin in conditioned media of numerous cultured cancer cell lines and normal endothelial cells prompted me to question the purpose of ephrin release. In this thesis I show that ephrin A1, a potent angiogenic factor, is released from several cancer cell lines and is a substrate for tissue transglutaminase, a multifunctional enzyme with the ability to form covalent crosslinks between substrate proteins. I show that tissue transglutaminase crosslinking primes soluble ephrin A1 to promote Eph A2 activity. These results suggest a role for soluble A-type ephrins in promoting Eph receptor activity at distant sites and also indicate that ephrin A1 may be acting as a soluble angiogenic factor during tumor neovascularization.

Title: Dynamical behaviour of matrix proteins from Mason-Pfizer Monkey Virus Author: Pavel Srb Department: Department of Low temperature physics Supervisor: doc. RNDr. Jan Lang, PhD. Abstract: We studied the oligomeric properties of betaretroviral nonmyristoylated ma- trix protein (MA) and its R55F mutant from the Mason-Pfizer monkey virus in solution by means of NMR spectroscopy. We have proven that the wild- type (WT) MA forms oligomers in solution. The final model of oligomeriza- tion of the WT MA was derived by concerted use of chemical shift mapping and diffusion-ordered spectroscopy measured on a set of protein samples with varying concentrations. We found that the Mason-Pfizer monkey virus WT MA exists in a monomer-dimer-trimer equilibrium in solution. Further a combination of NMR relaxation measurements and advanced analysis of molecular dynamics simulation trajectory provided an unprecedentedly de- tailed insight into internal mobility of matrix proteins of the Mason-Pfizer monkey virus. Strong evidence have been obtained that the oligomerization capacity of the wild-type matrix protein is closely related to the enhanced dynamics of several parts of its backbone on a nanosecond time scale. In- creased flexibility has been observed for two regions: the loop between he- lices α2 and α3 and the C-terminal...

Les données de séquençage des génomes ont révélé une nouvelle famille de protéines UPF0079, comprenant des protéines de fonction inconnue qui sont exclusivement et largement présentes chez les bactéries et qui possèdent un motif A de Walker dans leur séquence. La caractérisation biochimique et l'élucidation du rôle physiologique de cette famille contribueront à élargir nos connaissances en biologie fondamentale, et sont également un préalable vers le développement de nouveaux composés antimicrobiens. Notre étude sur YdiB, un archétype de cette famille chez Bacillus subtilis a révélé à la fois l‟autophosphorylation de YdiB et son activité de protéine kinase. L‟activité kinase de double spécificité Ser/ Thr et Tyr de YdiB semble nécessiter son oligomérisation et semble être stimulée par des molécules basiques telles que des polyamines naturelles ou la poly-L-lysine. Les 10 résidus les plus conservés chez cette famille ont été étudiés afin de mieux comprendre le mécanisme moléculaire de YdiB. Concernant la caractérisation fonctionnelle de la phosphorylation liée à YdiB, l‟étude de l‟opéron ydiA-B-C-D-E de B. subtilis nous a permis de montrer que YdiB et YdiC fonctionnent comme un couple de protéine kinase/phosphatase de deux protéines substrats dont les fonctions seraient liées aux ribosomes, YdiD et YdiE. Une co-localisation partielle entre YdiB et les ribosomes a été observée. En outre, YdiB est capable de phosphoryler des protéines ribosomiques appartennant aux deux sous-unités 50S et 30S, ainsi que deux GTPases impliquées dans la biogénèse des ribosomes, EngA et EngB. Nous avons également démontré que EngA phosphorylée par YdiB est un substrat in vitro de la phosphatase YdiC. Enfin, basé sur le phosphoprotéome de Bacillus subtilis, des peptides mimant des sites de phosphorylation in vivo ont été utilisés. Certains entre eux sont phosphorylés in vitro par YdiB. Deux de ces peptides appartiennent à la superoxyde dismutase, SodA, dont l'activité in vitro et après purification est régulée positivement via la phosphorylation par YdiB. Nous avons ensuite constaté que les cellules de B. subtilis dépourvues du gène ydiB sont plus sensibles aux agents oxidants tels que le paraquat ou la norfloxacine. Nous proposons que, in vivo, YdiB fonctionne comme une protéine kinase impliquée dans l‟activité et/ou la stabilité des ribosomes dans des conditions physiologiques normales, et YdiB contribuerait à protéger les cellules contre les dommages du stress oxydatif. / Genome sequencing data has revealed genes encoding uncharacterized protein family UPF0079 which are exclusively found in bacteria; broadly distributed in this kingdom and possess an ATP-binding motif in their sequences. Biochemical characterization and physiological role elucidation of UPF0079 will undoubtedly increase our fundamental biology knowledge, and also remain a prerequisite towards the development of new antimicrobial compounds. Our investigation on YdiB, an archetype of this family in Bacillus subtilis revealed both autophosphorylating and protein phosphotransferase activities. The dual-specificity Ser/Thr and Tyr kinase activity of YdiB seems to require oligomerization is upregulated by basic molecule activators such as natural polyamines or poly-L-lysine. The 10 most conserved residues were studied to gain insights into molecular mechanism of the kinase YdiB. To characterize the function of phosphorylation events linked to YdiB, starting with the B. subtilis ydiA-B-C-D-E operon we showed that YdiB and YdiC function as cognate protein kinase/phosphatase towards two ribosome-related protein substrates YdiD and YdiE. Some co-localization between YdiB and ribosomes were observed. Furthermore, YdiB is capable of phosphorylating both ribosomal 50S and 30S subunits as well as two ribosome-binding GTPases EngA and EngB. We also demonstrated that phosphorylated EngA by YdiB is an in vitro substrate of the phosphatase YdiC. Finally, based on the phosphoproteome pf Bacillus subtilis, peptides mimicking the in vivo phosphorylation sites were used. Some of them were found to be phosphorylated in vitro by YdiB, including two peptides which belongs to the superoxide dismutase SodA. The activity of purified SodA was then shown to be upregulated via phosphorylation by YdiB. We furthermore found that B. subtilis cells lacking ydiB become more sensitive to oxidative stress-causing agents such as paraquat or norfloxacin. We propose that in vivo, YdiB functions as a protein kinase involved in ribosome function in normal condition; and in protecting cells from oxidative stress damage.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Glycerol is a by-product of the biodiesel obtaining process and is highlighted due to its availability in the market and its high chemical functionality, presenting itself as a possible forerunner of a number of value-added compounds, e.g., their oligomers (di- and triglycerol). The characteristics of heterogeneous catalysts favor the transformation of glycerol valorization processes in even more sustainable routes. In this context, this paper proposes to evaluate the use of dolomite and eggshell as heterogeneous catalysts in the solventless oligomerization of glycerol. The materials were tested as catalysts in natural and calcined forms. The thermal process has modified the structure and morphology of the materials and their textural properties. Calcination was effective in increasing their catalytic activity. The calcined dolomite showed better catalytic performance, being capable of producing glycerol conversion around 97% with selectivity to diglycerol about 6,7% by reactions with a catalyst/glycerol mass ratio of 0,02; at 220  C, nitrogen flow and 24 hours. Using eggshells the best conditions were catalyst/glycerol mass ratio of 0,01 at 220  C and 24 hours, obtaining a conversion of approximately 75% and selectivity of 10,9 %. In both cases, there was formation of a high molecular weight product with non-newtonian and pseudoplastic fluid rheological behavior. Dolomite reusing tests pointed to its dissolution in the reaction product with consequent appearance of Ca and Mg in the samples, detected by ICP. There was a significant change in conversion and selectivity to diglycerol with two reuse cycles. The reaction conditions found are less severe than those reported in the literature with the use of synthetic catalysts, which added to the low cost of the material make its utilization promising in the glycerol oligomerization process. / O glicerol, subproduto do processo de obtenÃÃo do biodiesel, encontra-se em evidÃncia dada sua alta disponibilidade no mercado e por possuir alta funcionalidade quÃmica, apresentando-se como possÃvel precursor de uma sÃrie de compostos de valor agregado, por exemplo, seus oligÃmeros (di e triglicerol). As caracterÃsticas dos catalisadores heterogÃneos favorecem a transformaÃÃo dos processos de valorizaÃÃo do glicerol em rotas ainda mais sustentÃveis. Neste contexto, este trabalho propÃe-se a avaliar o uso da dolomita e da casca de ovo como catalisadores bÃsicos heterogÃneos na oligomerizaÃÃo do glicerol na ausÃncia de solvente. Os materiais foram testados como catalisadores nas formas natural e calcinada. O processo tÃrmico modificou a estrutura e a morfologia dos materiais bem como suas propriedades texturais. A calcinaÃÃo foi efetiva no aumento da atividade catalÃtica dos mesmos. A dolomita calcinada mostrou melhor desempenho catalÃtico permitindo a obtenÃÃo de conversÃo do glicerol em torno de 97 % com seletividade ao diglicerol de cerca de 6,7 %, em reaÃÃes com 2 % de catalisador, 220 ÂC, fluxo de nitrogÃnio e 24 horas de duraÃÃo. Quanto à casca de ovo as melhores condiÃÃes foram: carga de catalisador de 1 %, 220 ÂC e 24 horas, obtendo-se uma conversÃo de aproximadamente 75 % e seletividade de 10,9 %. Em ambos casos, houve a formaÃÃo de um produto de elevada massa molecular e comportamento reolÃgico nÃo-newtoniano e pseudoplÃstico. Os testes de reuso da dolomita apontaram para a dissoluÃÃo da mesma no produto reacional, com consequente aparecimento de teores de Ca e Mg nas amostras, detectados por ICP. Houve significativa alteraÃÃo da conversÃo e da seletividade ao diglicerol com 2 ciclos de reuso. As condiÃÃes reacionais encontradas sÃo menos severas que as reportadas na literatura com o uso de catalisadores sintÃticos, o que somado ao baixo custo do material tornam promissora sua aplicaÃÃo no processo de oligomerizaÃÃo do glicerol.

Escherichia coli transporter protein AcrB and its homologues are the inner membrane components of the Resistance-Nodulation-Division (RND) family efflux pumps in Gram-negative bacteria. It is well accepted that soluble proteins are only marginally stable, but such insight is missing for membrane proteins. The lack of stability data, including thermodynamic stability and oligomer association affinity is a result of intrinsic difficulties in working with membrane proteins. In addition, the degradation of soluble proteins in E. coli has been extensively studied whereas the degradation process of membrane proteins remains unclear. A focus of my thesis is the validation and development of methods used to measure the thermo- and oligomeric- stability of membrane proteins. I investigated the mechanism of a popular thermal-stability assay developed specifically for the study of membrane proteins uses a thiol-specific probe, 7-diethylamino-3-(4-maleimidophenyl)-4-methylcoumarin (CPM). I found that, contrary to current understanding, the presence of a sulfhydryl group was not a prerequisite for the CPM thermal stability assay. The observed fluorescence increase is likely caused by binding of the fluorophore to hydrophobic patches exposed upon protein unfolding. I then applied these methods in the study of three projects. In the first project, I investigated how suppressor mutations restore the function of AcrBP223G, in which the Pro223 to Gly mutation compromised the function of AcrB via disrupting AcrB trimerization. The results suggested that the function loss resulted from compromised AcrB trimerization could be restored through various mechanisms involving the compensation of trimer stability and substrate binding. In the second project, I created two AcrB fusion proteins, with C-terminal yellow fluorescence protein (YFP) and cyan fluorescence protein (CFP), respectively. YFP and CFP form a fluorescence resonance energy transfer (FRET) pair. Using this pair of fusion proteins, I studied AcrB assembly both in detergent micelles and in lipid bilayers. A positive cooperativity was observed in kinetic studies of association of AcrB trimer. Reconstitution experiment revealed that the association showed a higher FRET efficiency and faster association rate in liposome than in DDM. In the last project, I developed a fluorescence method to study the degradation of AcrB-ssrA by the ClpXP system. Comparing to the degradation of GFP-ssrA, degradation of AcrB-CFP-ssrA showed a lower maximum velocity and tighter binding to the enzymes with a positive cooperativity.

Depuis quelques années la demande en gazole dépasse la production des raffineries européennes et inversement pour les essences. L'objectif de cette thèse est de valoriser l'excédent d'essences et de satisfaire la demande en diesel en utilisant le procédé d'oligomérisation des oléfines. Nous nous sommes intéressés à l'oligomérisation du pentène qui, au contact d'un catalyseur solide acide, s'oligomérise en molécules plus lourdes de 10 à 25/30 atomes de carbone. Nous avons choisi les zéolithes et la mordénite en particulier comme catalyseur de la réaction. Afin d'améliorer le transport des molécules aux sites actifs nous avons modifié la texture des mordénites par la création d'un réseau secondaire de mésopores au sein de leurs cristaux, en utilisant deux traitements post-synthèse différents : la dessilication et la recristallisation. La dessilication génère des mésopores intra et inter-cristallins (de 10 nm à 100 nm de diamètre) par dissolution partielle de la zéolithe en présence d'une solution basique. La recristallisation conduit à une mésoporosité organisée et monodispersée en taille (petits mésopores de 4 nm) grâce à l'utilisation d'un agent structurant sous conditions hydrothermiques. Nous avons ainsi obtenu des mordénites micro-mésoporeuses de texture, porosité et acidité différentes en fonction du traitement appliqué. Finalement, après l'élaboration du micro-pilote expérimental, nous avons comparé les performances de nos catalyseurs optimisés de mordénites micro-mésoporeuses à celles des catalyseurs de référence (conversion, stabilité, sélectivité, rendement en oligomères C15-C20+, degré de branchement des produits) afin d'établir les relations structure-acidité-performances catalytiques. Nous avons mis en évidence l'impact positif de l'insertion de mésopores dans le catalyseur sur la conversion, la stabilité et le rendement en oligomères C15-C20+. Une méthodologie de caractérisation du degré de branchement des produits de réaction a également été mise au point pour compléter l'analyse des performances catalytiques. / Recently the demand in diesel has been exceeding the production of European refineries and, inversely for gasoline. The objective of this thesis is to increase the value of the gasoline excess and meet the demand in diesel using the olefin oligomerization process. We focused on the oligomerization of pentene, which can transform into heavier molecules from 10 to 25/30 carbon atoms in contact with a solid acid catalyst . We chose zeolites as catalysts and more specifically mordenite. To improve the molecular transport to the active sites we have modified the mordenite texture by creating a secondary mesoporous framework inside the crystals, using two different post-synthesis treatments: desilication and recrystallization. Desilication treatment generates intra and inter-crystalline mesopores (from 10 nm to 100 nm diameter) by partial dissolution of the zeolite in the presence of a basic solution. Recrystallization creates a well-organized mesoporosity with a uniform diameter (small mesopores of 4 nm) due to the use of an organic template of mesopores under hydrothermal conditions. Starting from the same parent mordenite we obtained micro-mesoporous mordenites with different textures, porosity and acidity properties depending on the treatment. Finally, after the development of the experimental pilot, we compared the performance (conversion, stability, selectivity, yield in oligomers C15-C20+, branching degree of the products) of our optimized catalysts of micro-mesoporous mordenite with some reference catalysts in order to establish relations between structure-acidity and catalytic performance. We highlighted the positive impact of the introduction of mesopores in the catalyst on the conversion, stability and yield in oligomers C15-C20+. A methodology to characterize the branching degree of the products has also been developed for completing the analysis of catalytic performances.

Les maladies amyloïdes sont des affections sévères caractérisées par la présence de dépôts extracellulaires fibreux susceptibles de toucher un ou plusieurs tissus du corps humain. Au cours de ma thèse, je me suis intéressée au peptide β amyloïde (Aβ), impliqué dans la maladie d’Alzheimer, ainsi que l’amyline ou Islet Amyloid PolyPeptide (IAPP), impliqué dans le diabète de type 2. Le mécanisme de formation des fibres a été décrit comme un processus en deux étapes : la nucléation, conduisant à la formation d’oligomères et la phase d’élongation conduisant à la formation des fibres. La première partie de ma thèse est consacrée à l’étude des premières étapes d’oligomérisation d’IAPP. Ce projet, qui a fait appel à différentes techniques biophysiques, a permis de montrer que le mécanisme d’oligomérisation d’IAPP était coopératif et caractérisé par l’absence d’espèces de faible poids moléculaire en solution. Ensuite, je me suis intéressée au rôle de l’histidine 18 d’IAPP et l’effet de la charge globale du peptide sur ses propriétés d’oligomérisation. Pour cela, une étude mutationnelle a été réalisée et l’analyse biophysique des mutants en présence de modèles lipidiques a été effectuée à pH 5,5 et à pH 7,4. Les résultats de cette étude ont montré que la substitution du résidu 18 ralentissait la formation des fibres et que le pH acide était globalement défavorable à l’oligomérisation. Enfin, j’ai étudié les interactions entre les peptides amyloïdes et des inhibiteurs potentiels d’origine synthétique ou naturelle. Différents modes d’action de ces inhibiteurs ont ainsi pu être caractérisés, selon leur interaction avec les monomères ou les oligomères des peptides étudiés. / Amyloid diseases, including Alzheimer's (AD), Parkinson's, Prion diseases and type 2 diabetes mellitus (T2DM), are characterized by the accumulation of insoluble fibrillar aggregates in tissues. These diseases are the result of the aberrant folding of proteins that constitute the main component of the fibrils. My thesis project focused on two amyloid peptides: β-amyloid peptide, a 40/42 residue peptide involved in AD, and Islet Amyloid PolyPeptide (IAPP), a 37 residue peptide linked with T2DM. Although the mechanism of oligomerization is still unclear, it is known to be a stepwise process that includes a nucleation phase, where the peptides are mainly monomeric and slowly form aggregates, followed by an elongation phase, characterized by the formation of large prefibrillar oligomers leading to mature fibrils. A first part of my project focused on the early stages of fibrillation of IAPP, using a set of complementary biophysical techniques. This study showed that the oligomerization pathway of IAPP involved no or short time lived oligomers favoring the formation of large aggregates. In a second step, I investigated the effect of residue 18 and global charge of IAPP by a mutational analysis of residue His18 and biophysical analysis at pH 5.5 and 7.4. The results showed that (1) the substitution of His18 slowed down the kinetics of fibrillation of IAPP by affecting the interactions between monomers, (2) acidic pH was unfavorable for the process. Finally, we examined the interaction of amyloid peptides with potential inhibitors of synthetic (sugar or fluor-based peptides) or natural origin (epigallocatechingallate). Different mechanisms of action could be characterized.

Catalytic ethylene oligomerization is a well understood industrially viable process. The large majority of scientific literature and patents concerning this process has been developed with the use of chromium catalysts. Commercial systems producing selective tri/tetramerization, non-selective oligomerization and polymerization are all based on this metal with the exception of a few systems based on other transition metals (Zr, Ti, Ni etc.). This versatility raises interesting questions about chromium’s unique behaviour. Essentially, selective or non-selective oligomerization and polymerization processes could be regarded as belonging to the same category of C-C bond forming reactions, though different mechanisms are involved. The first part of this thesis explores a variety of chromium complexes for ethylene oligomerization purposes. In order to gather further information about the unique behaviour of chromium, we have explored a variety of nitrogen and phosphorus containing ligands. We started with a simple bi-dentate anionic amidophosphine (NP) ligand and assessed the role of the ligand’s negative charge and number of donor atoms in determining the type of catalytic behaviour in relation to the metal oxidation state. This ligand proved capable of generating a series of chromium dimeric, tetrameric or polymeric and even heterobimetallic chromium-aluminate complexes in different valence states. This allowed us to isolate a “single component” self activating Cr(II) complex as well as a rare example of mixed valence Cr(I)/Cr(II) species. Additionally, each of these species acted as switchable catalyst depending on the type of co-catalyst

La conversion du méthanol par les zéolithes est l'une des applications les plus prometteuses pour l'obtention d'hydrocarbures (oléfines, essences, gasoils) à partir de sources alternatives au pétrole (gaz naturel, charbon, biomasse). Dans cette thèse, un procédé catalytique multi-étapes permettant la conversion du méthanol en hydrocarbures à longue chaîne a été imaginé.Le méthanol est converti en oléfines légères par différents catalyseurs zéolithiques dans un réacteur à lit fixe sous flux continu et en phase gazeuse. L'utilisation de la ferrierite dessilicatée, de la chabazite désaluminée, de la MCM-22 et de la MCM-36 est détaillée. Les oléfines inférieures sont ensuite oligomérisées. L'oligomérisation de l'éthylène catalysée par des solides mésoporeux de type MCM-41 échangés au nickel et la co-oligomérisation des oléfines inférieures par catalyse acide sur H-MCM-41 ont été étudiées. Ces réactions ont été mises en oeuvre dans un autoclave semi-continu de type slurry. / Methanol conversion into hydrocarbons (olefins, gasoline and diesel fuel) over zeolites is one of the most promising applications involving non-oil based sources (natural gas, coal, and biomass). In this thesis, a multi-step catalytic process for converting methanol into long-chain hydrocarbons has been designed.Methanol was converted into light olefins by different zeolitic catalysts in a fixed bed reactor under continuous flow in gas phase. The use of dessilicated ferrierite, dealuminated chabazite, MCM-22 and MCM-36 has been investigated. Then, the lower olefins were oligomerized. The oligomerization of ethylene catalyzed by nickel exchanged mesoporous MCM-41 and co-oligomerization of lower olefins by H-MCM-41 acid catalyst were studied. These reactions were performed in a gas-slurry reactor operating in semi-batch mode.

Orientadores: Marcelo Menossi Teixeira, Ricardo Aparicio / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-27T14:13:51Z (GMT). No. of bitstreams: 1 Soares_JoseSergiodeMacedo_D.pdf: 4995080 bytes, checksum: ad3458f447f7044749e0ee6cb95f4315 (MD5) Previous issue date: 2013 / Resumo: O agronegócio da cana de açúcar movimenta cerca de R$ 40 bilhões por ano no Brasil. A cadeia produtiva da cana de açúcar como atividade na economia é responsável por 1,5% do produto interno bruto (PIB) nacional e um dos principais componentes econômicos é a quantidade de sacarose acumulada nos colmos. No entanto, a síntese de sacarose e sua acumulação em plantas superiores é o resultado do produto de uma extensa rede de interações. Quando descarregada nas células do parênquima de armazenamento, a sacarose é metabolizada por diferentes enzimas, sendo a UDP-glucose pirofosforilase (UGPase) uma das enzimas responsáveis pela síntese de sacarose em cana de açúcar. O objetivo deste trabalho foi avaliar o padrão de expressão do gene ScUGPase-1 e os mecanismos regulatórios que controlam a atividade da proteína UGPase de cana de açúcar. Análises por RT-qPCR revelaram que a expressão do gene ScUGPase-1 diminui ao longo da maturação dos colmos e o gene é mais expresso nos entrenós em comparação com o tecido de folha. Porém, nenhuma diferença de expressão significativa foi observada entre dois cultivares contrastantes em teor de sacarose. In vivo, a localização subcelular da proteína ScUGPase-1 indicou uma associação à membrana nos tecidos de folha e colmo. Utilizando anticorpo primário fosfo-específico, observamos a fosforilação da proteína ScUGPase-1 apenas na fração solúvel e microssomal do tecido de folha. In vitro, a proteína ScUGPase-1 formou um complexo com a proteína recombinante caseína quinase 1 (CK1) e sua atividade foi afetada por agentes óxido-redutores. Para complementar os dados de óxido-redução, análises de espalhamento de luz a baixo ângulo (SAXS) forneceram o primeiro modelo estrutural do dímero da proteína ScUGPase-1 em solução, destacando que a interface de dimerização está localizada na região C-terminal. Os dados indicam que a fosforilação, interação protéica e oligomerização podem exercem um papel importante na regulação da proteína ScUGPase-1 durante a síntese de sacarose em cana de açúcar. / Abstract:The sugarcane agribusiness generates around R$ 40 billion per year in Brazil, while the entire supply chain of sugarcane is responsible for 1.5% of the gross domestic product (GDP). Sugarcane productivity is mainly determined by the accumulation of sucrose in the culms. However, the synthesis and accumulation of sucrose in plants is the result of an extensive network. When sucrose is unloaded in the storage parenchyma cells, it is metabolized by different enzymes, and UDP-glucose pyrophosphorylase (UGPase) is one of the enzymes responsible for the synthesis of sucrose in sugarcane. The objective of this work was to gain insights on the ScUGPase-1 expression pattern and the regulatory mechanisms that control protein activity. ScUGPase-1 transcript levels were negatively correlated with sucrose content in the internodes and only a slight difference in the expression pattern was observed between two cultivars that differ in their sucrose content. The intracellular localization of ScUGPase-1 indicated association with membranes in both leaves and internodes. Using a phospho-specific antibody, we observed that ScUGPase-1 was phosphorylated in vivo in the soluble and membrane fractions from leaves, but not from internodes. In vitro, the purified recombinant enzyme interacted with recombinant protein casein kinase 1 and its activity was affected by redox modification. To complement the redox data, Small-Angle X-ray Scattering provided the first structural model of the dimer of sugarcane UGPase in solution, highlighting that the dimer interface is located at the C-terminal. The data indicated that phosphorylation, protein interaction and oligomerization may play an important role in the regulation of ScUGPase-1 activity / Doutorado / Genetica de Microorganismos / Mestre em Genética e Biologia Molecular