Dissertations / Theses on the topic 'Histidine'
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Quezada, Cindy Maria Richards John Gray Harry B. "Histidine phosphorylation in bacterial chemotaxis /." Diss., Pasadena, Calif. : California Institute of Technology, 2003. http://resolver.caltech.edu/CaltechETD:etd-05302003-145522.
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Kumar, Amit. "The enantioselective synthesis of histidine analogues." Thesis, Queen Mary, University of London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417598.
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Wang, Liang. "Structural characterisation of Histidine Kinase 2." Thesis, Queen Mary, University of London, 2018. http://qmro.qmul.ac.uk/xmlui/handle/123456789/33933.
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Two-component systems (TCS) are the predominant signal transduction pathways in prokaryotes, being present also in eukaryotic organisms, such as algae, fungi and yeast, and higher plants. TCSs play an important role in environmental signal perception and response, essentially implementing adaptation to the surrounding environment. Histidine Kinase 2 (Hik2) in cyanobacteria is a typical sensor histidine kinase, one component of a TCS, and has been identified to be a homologue protein of Arabidopsis Chloroplast Sensor Kinase (CSK). Previous research has elucidated Hik2 to regulate photosynthetic gene transcription with two response regulators, Rre1 and RppA via phosphorylation. A typical histidine kinase contains a variable sensor domain and a conserved kinase domain. It usually functions as a homodimer. This thesis describes the structural characterisation of Hik2, probing particularly its discovered oligomeric states. Results obtained from size exclusion chromatography, native-PAGE, chemical cross-linking analyses and mass spectrometry, amongst others, have shown a variety of Hik2 structural populations exist, further validated by negative stain transmission electron microscopy coupled to single particle analysis. Hik2 protein exists predominantly as a hexamer in low salt conditions, and adding NaCl dissociates hexamers into tetramers, critical for the autophosphorylation activity of Hik2. Thus, a model is proposed for the constitution change of Hik2 oligomers when salt concentration differs. In addition, the sensor domain is typically responsible for detecting environmental input, however, it is not yet clear how Hik2 and CSK sense signals. In this thesis, the structures of Hik2 and CSK sensor domains were analysed and discussed, to aid our understanding of their mechanism of signal perception and transduction.
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Lindgren, Karin E. "The Histidine-rich Glycoprotein in Reproduction." Doctoral thesis, Uppsala universitet, Institutionen för kvinnors och barns hälsa, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-300769.
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Infertility affects 15% of reproductive-aged couples. The milieu surrounding the growing embryo is of outmost importance, and should be optimised during in vitro fertilisation (IVF). Many biological processes, such as angiogenesis, coagulation, and immune processes need to be well regulated for a pregnancy to occur and progress normally. Histidine-rich glycoprotein (HRG) is a plasma protein that regulates components of these systems by building complexes with various ligands. A single nucleotide polymorphism (SNP) in HRG, denoted HRG C633T, seem to be of importance for IVF treatment outcomes. The aim of this thesis was to further investigate the proposed human fertility effects of the HRG C633T SNP. According to the findings of this thesis, the HRG C633T genotype is associated with primary recurrent miscarriage. Male HRG C633T genotype is associated with semen characteristics in infertile men, and pregnancy rates following IVF. However, the distribution of the HRG C633T SNP does not differ between infertile and fertile couples. We further examined the role of the region surrounding the HRG C633T SNP for regulation of endometrial angiogenesis and human embryo development. The region affects primary endometrial endothelial cell migration, proliferation and tube-formation in vitro but does not appear to affect human embryo development. No effect of the HRG peptide was noted on the secretome of human embryos. However, early embryos secrete proteins into the surrounding culture media and the level of secretion of VEGF-A, IL-6, EMMPRIN and PlGF is greater in embryos of higher developmental stages. In conclusion, the HRG C633T genotype appears to play a role only if infertility is established. The region surrounding HRG C633T SNP is of relevance in vitro for regulation of human endometrial endothelial cell angiogenesis. To predict which embryos to transfer in IVF, we have highlighted a number of proteins of interest for further investigation.
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Hungaro, Jean Bernard. "Etude physico-chimique de la chélation du cuivre (II) par des acides aminés (histidine et ses dérivés 1 et 3 méthylés)." Paris 7, 1992. http://www.theses.fr/1992PA077322.
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DUMAS, FRANCOISE. "Excretion urinaire de la 3 methyl histidine chez l'enfant : application a l'etat nutritionnel des mucoviscidoses : etude preliminaire." Lyon 1, 1988. http://www.theses.fr/1988LYO1M279.
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Martel, Alexandre. "Caractérisation de la position 48 du récepteur phoQ de Salmonella enterica serovar typhimurium." Sherbrooke : Université de Sherbrooke, 2001.
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Montagne, Martin. "Caractérisation des activités catalytiques du récepteur histidine kinase phoQ de Salmonella enterica serovar Typhimurium et des mutants de la position 179." Sherbrooke : Université de Sherbrooke, 2001.
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Souza, Elaine Costa [UNESP]. "Análise da expressão gênica global de mutantes de Xanthomonas citri subsp. citri." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/102819.
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O cancro cítrico é uma das principais doenças da cultura do citros, provocando lesões nas folhas, ramos e frutos, tendo como consequência a queda dos frutos e folhas, o que leva à perdas significativas na produção. A partir do sequenciamento completo do genoma da bactéria gram-negativa Xanthomonas citri subsp. citri (Xac), agente causal do cancro cítrico, abriu-se a possibilidade da utilização de estratégias de análise genômica funcional no estudo da função de genes da bactéria relacionados com a infecção na planta e com o desenvolvimento da doença. Uma das estratégias utilizadas foi a obtenção de mutantes de Xac contendo genes relacionados à patogenicidade e virulência interrompidos pelo método de mutagênese insercional aleatória utilizando o transposon Tn5 (LAIA et al., 2009). No presente trabalho a técnica de microarranjos de DNA foi utilizada para avaliar a expressão global de genes de dois mutantes de Xac 72 h após a infecção in planta. Em um dos mutantes (8B7) o gene interrompido foi o xrvA, um regulador de virulência, e no outro mutante (18D6) o gene interrompido codifica uma histidina quinase híbrida sensora que faz parte de um sistema de transdução de sinal de dois componentes. Os resultados das hibridizações revelaram um total de 553 genes diferencialmente expressos para os dois mutantes estudados quando comparado com o genótipo selvagem (Xac 306), sendo 323 no mutante 8B7 e 230 no mutante 18D6. Esses genes foram divididos em diferentes categorias funcionais e uma análise funcional comparativa revelou que eles podem desempenhar um papel importante no processo de patogenicidade
Citrus canker is a major disease affecting citrus crops worldwide, causing lesions on leaves, branches and fruits that results in the falling of fruit and leaves, leading to significant losses in orange production. The complete genome sequencing of Xanthomonas citri subsp. citri (Xac), a Gram-negative bacteria and the causal agent of citrus canker, allowed the possibility of using functional genomic strategies to study the function of genes related to plant infection and disease development in this bacteria. One strategy was to produce mutants for phatogenicity and virulence genes by random insertional mutagenesis using Tn5 Transposon (LAIA et al., 2009). In the present work DNA microarray analysis was used to evaluate the global gene expression profile of two Xac mutants after 72 hours of plant infection. One mutant (8B7) carry a mutation in the xrvA gene (XAC1495), a virulence regulator, and the other (18D6) carry a mutation in a hybrid histidine quinase sensor of a two-component signal transduction system. The results revealed a total of 553 differentially expressed genes for the two mutant strains compared with Xac wild type, with 323 in the mutant 8B7, and 230 in the mutant 18D6. These genes were allocated into several functional categories and a comparative functional analysis showed that they can play an important role in the pathogenicity and virulence of Xac
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Armstrong, Ellen Pauline. "Peptide histidine isoleucine : radioimmunoassay and immunohistochemical studies." Thesis, Queen's University Belfast, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335983.
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Lohkamp, Bernhard. "Structural studies on histidine metabolism in microorganisms." Thesis, University of Glasgow, 2003. http://theses.gla.ac.uk/9065/.
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Histidine is an important amino acid involved in enzyme catalysis and metal binding in many proteins. Bacteria, fungi and plants synthesise histidine via the 10 step histidine pathway, whereas histidine is an essential amino acid required in the diet of animals. The synthesis of histidine is energetically expensive with about 41 ATP needed to produce one histidine. As a result the histidine biosynthetic pathway is tightly regulated and some microorganisms can consume excess histidine as a nitrogen and carbon source via a histidine utilisation (hut) pathway. The absence of a histidine biosynthetic pathway in mammals makes it a good target for the development of antimicrobial and antifungal drugs as well as herbicides. In addition to an overall regulation of the histidine synthesis by charged histidyl-tRNA and histidyl-tKNA synthetase, the histidine pathway is regulated in various ways by the first enzyme of the pathway ATP-phosphoribosyltransferase (HisG). The enzyme catalyses the condensation of ATP and phosphoribosylpyrophosphate (PRPP) to form phosphoribosyl-ATP (PR-ATP) and is feedback regulated by histidine, the end product of the pathway. Furthermore, HisG is inhibited by its product PR-ATP and also by AMP and ppGpp, reflecting the overall energy status of the cell. Inhibition of HisG coincides with a change in aggregation state, in which the active dimers form inactive hexamers. Some bacterial genomes contain a hisG gene, which lacks about 80 residues at the C-terminus, but have an additional gene, hisZ. This short form of HisG itself is inactive and forms an active complex with HisZ. This thesis describes the solution of the 3-dimensional structures of the hexameric forms of bacterial HisGs by X-ray crystallography. The structure of the Escherichia coli HisG was determined in the presence of the inhibitors AMP and PR- ATP. Additionally, a histidine-bound structure of HisG from the thermophilic bacterium Methanobacteriim thermoautotrophicum has been obtained. The monomer of HisG comprises of three a/p domains. The first two domains show a periplasmic protein-like fold with the active site located in a cleft between the two domains. The C-terminal domain, similar to Pn signal transduction proteins, binds histidine and is mainly involved in the formation of the hexamers. Additionally the structure of HisG represents a new type of phosphoribosyltransferase. The structure of the binary complex with AMP has allowed the identification of the PRPP binding site and explains the competitive inhibition by AMP with respect to both substrates. Furthermore the AMP binary structure and the PR-ATP-complexed structure identified the binding site of the ATP purine ring. The histidine-bound structure explains the histidine inhibition by disruption of the PRPP binding site on the dimer interface by elongation of the dimer and hence the hexanier. A mode of inhibition common to all the inhibitors investigated is the formation of hexamers upon inhibitor binding which buries the active sites in the inside of the hexamer and makes the sites less accessible to the substrates. Mutational and kinetic analysis showed that the extra C-terminal domain in the long form of HisG is not essential for activity. Subsequently, it was demonstrated that the naturally short form of HisG can be activated by thermal energy. This suggests a tense conformation for the short form of the enzyme which can be relaxed and activated by forming an oligomeric complex with HisZ. The structure of an unidentified protein in the histidine utilisation (hut) pathway from Pseudomonas aeruginosa, PAS104, was determined to better than 1 A resolution. Solution of the structure was accomplished by a unique approach combining SIRAS phasing with direct methods (Sayre equation). PAS104 is an all-beta protein with a bicupin fold. One of the P-barrels is open and accommodates a small molecule binding site. A different conformation of PAS 104 was obtained from a second structure solved using a different crystal form. Comparison of the structures and interactions in the active site identifies glutamate or derivatives (intermediates in the hut pathway) as possible substrates, which can induce a conformational change and may give PAS104 a regulatory function.
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DELORME, CHRISTINE. "Polymorphisme de l'operon histidine chez les lactocoques." Paris 7, 1992. http://www.theses.fr/1992PA077048.
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Les souches de l. Lactis subsp. Lactis isolees du milieu laitier ne peuvent pas synthetiser d'histidine a l'inverse des souches isolees de vegetaux. Les genes impliques dans la voie de biosynthese de l'histidine ont ete clones a la fois dans une souche d'origine vegetale et d'origine laitiere. Ces genes sont organises en un operon, comprenant 12 cadres ouverts de lecture dont 8 codent pour des proteines qui presentent de l'homologie avec les enzymes impliquees dans la voie de biosynthese de l'histidine. L'operon non fonctionnel, isole d'une souche de lactocoques laitiers, presente des deletions d'une paire de bases qui conduisent a la synthese de 5 proteines tronquees, ainsi que des substitutions qui expliquent l'auxotrophie des souches laitieres. Une partie de l'operon histidine provenant de l. Lactis subsp. Cremoris, a ete sequence et a revele une zone de forte homologie de 80%, ainsi qu'une zone de faible homologie de 50% par rapport aux autres souches. L'analyse statistique du contenu en bases gc, du biais de codon et la presence de repetitions directes inhabituelles, suggerent que cette region de faible homologie de l'operon histidine aurait evolue plus par un transfert de genes que par une forte derive genetique
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Khatchadourian, Rafael Aharon. "Characterization of histidine-tagged NaChBac ion channels." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116024.
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Imaging tools in cellular and molecular biology have long relied on organic fluorophores to observe microorganisms or various cell constituents. The advent of semiconductor nanoparticles known as quantum dots (QDs) has offered the possibility to use this new class of fluorescent probes with very advantageous optical properties in cell biology. The imaging of transmembrane potential and ionic currents is of significant importance for monitoring the activity of the cell. It remains possible with relatively complicated instruments and methods such as patch clamping. A complementary approach to view the dynamics of ion channels with modern and efficient fluorophores is therefore of great interest to the field of biology in general.We developed a construct based on the FRET signal between QDs and organic fluorescent dyes to monitor the conformational changes of voltage gated sodium channels. The amino acid histidine was used as a "landing platform" for QDs and the bacterial sodium channel NaChBac was chosen for testing. This study focused on the preliminary steps of the project and aimed to characterize the electrophysiological behavior of the histidine-tagged channel. The whole-cell configuration of patch clamping was the tool we used to understand the differences between the wild-type and the histidine-tagged variants of the channels. We also explore the possibility to land QDs on the histidine tag.
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Valer, Luca. "Histidine ligated Iron-Sulfur Proteins and Peptides." Doctoral thesis, Università degli studi di Trento, 2022. https://hdl.handle.net/11572/355641.
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Iron-sulfur clusters play a fundamental role in biology and are believed to be ancient cofactors that could have played a role in early protometabolic systems. Thus far, redox active, prebiotically plausible iron-sulfur clusters have always been obtained through cysteine coordination to the iron ions. However, extant iron-sulfur proteins can be found to exploit other modes of binding, including ligation by histidine residues, as seen with [2Fe-2S] Rieske and MitoNEET proteins. In this thesis, we investigated the ability of cysteine- and histidine-containing proteins and peptides to coordinate mononuclear [1Fe-0S] centers and a [2Fe-2S] clusters. The iron-sulfur peptides were characterized by UV-vis, circular dichroism, and paramagnetic NMR spectroscopies and cyclic voltammetry. Small (≤ 6 amino acids) peptides can coordinate [2Fe-2S] clusters through a combination of cysteine and histidine residues with similar reduction potentials as their corresponding proteins. Such complexes may have been important for early cell-like systems.
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Clair, Bertrand. "Contributions à la compréhension des phénomènes de nucléation induite par laser : applications à la glycine et études préliminaires sur l'histidine et l'acide glutamique." Thesis, Châtenay-Malabry, Ecole centrale de Paris, 2014. http://www.theses.fr/2014ECAP0056/document.
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Le contrôle de la fabrication des structures cristallines des médicaments est un enjeu crucial pour l'industrie pharmaceutique. Plusieurs exemples ont montré qu'une mauvaise maîtrise du polymorphisme conduisait à des situations dramatiques. Récemment, une méthode permettant la maîtrise du polymorphisme de molécule organique dissoute en solution à l'aide de la polarisation d'un faisceau laser a été découverte aux Etats-Unis. Cette thèse étudie l’effet du laser sur des solutions aqueuses de molécules de glycine, L – (+) – histidine, D – (-) – et L – (+) – acide glutamique. Afin de réaliser l’étude, un montage expérimental a été construit permettant le contrôle de nombreux paramètres et une méthode spécifique de travail a été développée afin de limiter fortement l’aléa expérimental. Une étude multi-paramètres incluant l’effet comparé des polarisations linéaire et circulaire dans du H2O et du D2O de la nucléation induite par laser non-photochimique (NPLIN) de la glycine a été menée. Une étude préliminaire de l’effet du laser sur les solutions d'histidine et de l' acide glutamique a également été réalisée. Il est montré que le solvant est un facteur déterminant du contrôle du polymorphisme. Toutefois, la conjonction de la polarisation et de la concentration a une influence sur les polymorphes de glycine obtenus dans le H2O. Les résultats obtenus permettent de contribuer à la compréhension du mécanisme en améliorant l'hypothèse initiale de l'effet KerrPolymorphism control of drug molecules is one the main challenges facing drug companies. Several examples have shown than an uncontrolled polymorphism crystallization could lead to dramatic situation. One the most recent progress in the polymorphism control is the unwanted discovery of polymorphic selective crystallization of organic molecule dissolved in solution based on the laser beam polarization. This thesis deals with the implantation of this method in France for the first time based on a methodology limiting experimental hazard and a special design experimental device dedicated to this study. This work is based on an important review of known results of the field and published for the first time. An important multifactor study was done on glycine, histidine and glutamic acid, which allows to improve knowledges on the putative initial mechanism based on the Kerr effect. It has been established that the solvent is the dominant factor, letting laser polarization as the third factor for polymorphism control after concentration
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Zu, Xin Lin. "Methods for the detection, purification and characterisation of histone H4 histidine kinase and the analysis of protein histidine phosphorylation." University of Western Australia. Biochemistry and Molecular Biology Discipline Group, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0092.
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[Truncated abstract] Protein phosphorylation, one of the most important forms of post-translational modification, has been demonstrated to play crucial roles in regulation of cell function. Phosphorylation of protein serine, threonine and tyrosine residues has been the most thoroughly investigated, taking advantage of the acid-stable character of these phosphohydroxyamino acids. Whereas, the cellular occurrence of acid-labile phosphoamino acids, such as phosphohistidine, phosphoarginine and phospholysine was often underestimated due to the acid treatments employed by most of the traditional phosphoamino acid analysis methods. The biological roles of histidine kinases (HKs) in prokaryotes are well understood in contrast to those of HKs in eukaryotes, especially in mammalian cells. However, the evidence has shown that phosphohistidine comprised 6% of phosphoamino acids of the basic nuclear proteins in eukaryotes (Matthews, 1995) and there was more phosphohistidine than phosphoserine in rat liver mitochondria (Bieber and Boyer, 1966). More significantly, phosphohistidine was revealed to be the major phosphoamino acid in phosphorylated histone H4 in regenerating liver in vivo (Chen et al., 1974) and the Walker-256 carcinosarcoma cells in vitro (Smith et al., 1974). Recently, the histone H4 histidine kinase (HHK) activity of human hepatocellular carcinoma (HCC) tumour tissue was measured to be 400 times higher than the normal liver tissue surrounding the tumour. HepG2 cells (HCC cell line) and PIL-2 cells (a p53 knockout mouse tumorigenic liver progenitor cell line) also displayed high HHK activity (Tan et al., 2004). The above observations suggested that HKs and HHKs are playing important roles in both prokaryotes and eukaryotes, including mammals. One major obstacle in the study of HHK study has been the lack of knowledge of the amino acid sequence of an HHK. Attempts at purifying and identifying the HHK from yeast led to the partial purification of a yeast HHK protein(s) at 32kDa (Huang et al., 1991). However, the amino acid sequence of the HHK has not yet been established. ... The success of the separation was demonstrated by the MALDI-TOF-MS and/or ESI-MS spectra of the RP-HPLC fractions. These achievements suggested that it is possible to detect phosphohistidyl histone H4 in vivo using MS under experimental conditions where phosphohistidine is relatively stable. The study in this thesis represents the progression of HHK research in various aspects, including the yeast HHK purification and identification, mammalian HHK partial purification and the methodological developments in detecting histone H4 histidine phosphorylation using MS. Furthermore, new information regarding the physical characteristics of yeast HHKs and its potential role in cellular biology have been documented. It is anticipated that knowledge generated in these studies will contribute to the insight and the understanding of the biological significance of HHK in yeast and mammalian cells.
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Berton, Juliana. "ESTUDO DO PAPEL DA HISTIDINA, HISTAMINA E ANTAGONISTAS HISTAMINÉRGICOS NA PROGRESSÃO E DIFERENCIAÇÃO CELULAR EM UM MODELO DE MELANOMA MURINO." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2015. http://tede2.uepg.br/jspui/handle/prefix/91.
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Histidine is an important amino acid in the differentiation of some cell types, such as hepatocytes, for example. Histamine is synthesized from histidine is present in many cancer types, including melanoma. This cancer has as characteristics no differentiated cell and the production a high amount of histamine. The purpose of this work was to study the effects of a histidine supplementation on differentiation and tumor progression. In vitro cell viability were performed by neutral red and MTT assays with histidine at 0,01, 0,1, 0,3, 1,0, 3,0, 10 and 20 mM cimetidine at 0,01, 0,1, 0,3, 1,0, 3,0, 10 mM, 10 mM histidine association cimetidine + 0,01 mM and 10 mM cimetidine association + 0,01 mM histidine and evaluated after 24, 48 and 72 hours using B16F10 cells and morphological analysis additionally performed. Histamine at 0,01, 0,1, 1 and 10 mM, terfenadine at concentrations 1, 10, 100 nM and 1 uM and thioperamide at concentrations 1, 10, 100 nM and 1 uM were also assessed by using the MTT cell B16F10. ELISA was performed to quantify histamine with cell culture supernatant treated with histidine, histamine, terfenadine, cimetidine, and thioperamide. For in vivo assays were used C57BL6/J mice underwent implantation of tumor cells and subsequently treated with histidine solution at a dose of 21.4 mg/kg cimetidine 343.3 mg/kg and association between both and evaluated for 11 days as the tumor growth were used. Histological analysis, hematological and biochemical determinations were also performed. Data were analysed by ANOVA One-Way, and Tukey post-test. The results of the MTT viability test, showed cell viability decreased histidine at a concentration of 0,01 mM in 72 hours, cimetidine in concentrations 3 to 10 mM at 48 and 72 hours and cimetidine 10 mM /histidine 0,01 mM association in 48 and 72 hours, results also found in neutral red. Histamine decreased the cell viability of B16F10 cells at 20 mM concentration in 48 h and concentrations 1 and 10 mM at 72 hours, terfenadine decreased cell viability at all concentrations tested at 24 h and stayed up to 10 nM 72 hours and thioperamide decreased the cell viability at all concentrations tested 72 hours MTT assay. In the morphological analysis it was observed that at lower concentrations of histidine discrete cell rounding occurred and the appearance of "blebs" and the highest concentrations of vacuolated cytoplasm. Cimetidine treated cells showed characteristics of apoptosis. The association histidine 0,01 mM/cimetidine 10 mM caused cell death. The histamine ELISA test showed that the treatment with the histamine H1 antagonist may increase or decrease production of histamine and its receiving treatment led to thioperamide produce less or blocking of histamine H3 receptors allows a greater uptake of histamine. In experiments in vivo treatments with histidine and cimetidine inhibited tumor growth by the seventh day of treatment. Biochemical determinations of AST, ALT showed no toxicity after treatment. The histological findings, the group treated with histidine showed necrotic areas and the cimetidine group showed leukocyte infiltration and promoted stimulation of angiogenesis. Metastases were not found in any of the organs analyzed groups. It was concluded that histidine plays an important role in tumor progression and stimulating or inhibitory depending on the dosage/day of treatment.
A histidina é um aminoácido importante fator na diferenciação de alguns tipos celulares, como hepatócitos, por exemplo. A histamina, sintetizada a partir da histidina, está presente em muitos tipos de câncer, entre eles o melanoma. Esse tipo de câncer tem como características a não diferenciação celular e a produção de grande quantidade de histamina. O propósito deste trabalho foi estudar os efeitos de uma suplementação de histidina sobre a diferenciação e progressão tumoral. Os ensaios in vitro de viabilidade celular MTT e vermelho neutro foram realizados com histidina nas concentrações 0,01, 0,1, 0,3, 1,0, 3,0, 10 e 20 mM, cimetidina nas concentrações 0,01, 0,1, 0,3, 1,0, 3,0, 10 mM, associação histidina 10 mM + cimetidina 0,01 mM e associação de cimetidina 10 mM + histidina 0,01 mM e avaliados após 24, 48 e 72 horas utilizando-se células B16F10 e adicionalmente realizada a análise morfológica. Histamina nas concentrações 0,01, 0,1, 1 e 10 mM, terfenadina nas concentrações 1, 10, 100 nM e 1 μM e tioperamida nas concentrações 1, 10, 100 nM e 1 μM também foram avaliadas pelo MTT utilizandose células B16F10. Foi realizado teste de ELISA para quantificação de histamina com sobrenadante de cultura celular tratada com histidina, histamina, terfenadina, cimetidina e tioperamida. Para o ensaio in vivo foram utilizados camundongos C57BL6/J, submetidos ao implante de células tumorais e posteriormente tratados com solução de histidina na dose de 21,4 mg/kg, cimetidina na dose de 343,3 mg/kg e associação entre ambas e avaliados por 11 dias quanto ao crescimento tumoral. Avaliações hematológicas, determinações bioquímicas e análise histológica também foram realizadas. Os dados obtidos foram submetidos à análise estatística ANOVA 1-VIA, e pos-test Tukey. Como resultados no teste de viabilidade MTT, a histidina diminuiu a viabilidade celular na concentração de 0,01 mM em 72 horas, da cimetidina nas concentrações de 3 e 10 mm em 48 e 72 horas e da associação cimetidina 10 mM/histidina 0,01 mM em 48 e 72 horas, resultados também encontrados no vermelho neutro. A histamina diminuiu a viabilidade celular das células B16F10 em 48 h na concentração de 20 mM e em 72 horas nas concentrações de 1 e 10 mM, a terfenadina diminuiu a viabilidade celular em todas as concentrações testadas em 24 h, permanecendo a de 10 nM até 72 horas e a tioperamida diminuiu a viabilidade celular em todas as concentrações testadas em 72 horas no ensaio de MTT. Na análise morfológica observou-se que nas menores concentrações de histidina ocorreu discreto arredondamento celular e aparecimento de “blebs” e nas concentrações maiores vacuolização de citoplasma. As células tratadas com cimetidina apresentaram indícios de apoptose. A associação histidina 0,01 mM/cimetidina 10 mM provocou morte celular. O teste de ELISA para histamina revelou que o tratamento com o antagonista H1 de histamina pode aumentar a produção de histamina ou diminuir sua receptação e o tratamento a tioperamida levou a uma menor produção de histamina ou o bloqueio dos receptores H3 permitindo uma maior recaptação de histamina. Na experimentação in vivo os tratamentos com histidina e cimetidina inibiram o crescimento tumoral até o sétimo dia de tratamento. As determinações bioquímicas das enzimas transaminase oxalacética e transaminase pirúvica revelaram que não houve toxicidade após os tratamentos. Nas avaliações histológicas, o grupo tratado com histidina apresentou áreas necróticas e o grupo cimetidina apresentou infiltrado leucocitário e promoveu estímulo da angiogênese. Metástases não foram encontradas nos órgãos analisados de nenhum dos grupos. Concluiu-se que a histidina tem um papel importante na progressão tumoral sendo inibitório ou estimulante dependendo da dosagem/dias de tratamento.
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Balboa, Marie Sophie. "Monovalent cation effects on histidine kinase CheA activity." Thesis, University of Colorado at Boulder, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1589936.
Full textAbstract:
CheA is a multi-domain histidine kinase believed to be a central component of all bacterial and archaeal chemosensory arrays. The best studied CheA proteins are those of Escherichia coli, Salmonella typhimurium, and Thermotoga maritima. The P4 catalytic domain of CheA is of particular interest due to its role in ATP binding and auto-phosphorylation of the substrate His residue on the P1 substrate domain, a process which involves Mg 2+ in the P4 domain ATP-binding pocket. CheA auto-phosphorylation reaction has also long been known to be sensitive to the monovalent cation composition of the reaction buffer. Recent studies in GHKL superfamily members MutL (from E coli) and BCK (from Rattus norvegicus) demonstrated improved activity in the presence of monovalent K +. Here experimental and computational analyses assess the effect of monovalent cations on the activity of Salmonella typhimurium CheA, and generate a model for a putative monovalent cation binding pocket. The findings show that CheA prefers the physiological K+ ion over the other monovalent cations tested, indicating the site is specific and tuned to possess the appropriate K+ affinity for the cytoplasmic environment.
19
McGinnity, Dermot F. "An essential histidine in bacterial cytochrome C peroxidases." Thesis, University of Edinburgh, 1996. http://hdl.handle.net/1842/30475.
Full textAbstract:
Cytochrome c peroxidase from Paracoccus denitrificans was modified with the histidine-specific reagent diethylpyrocarbonate. The reaction can be followed spectroscopically and, at low excess of reagent, one mol of histidine was modified in the oxidised enzyme. The agreement between the spectrophotometric measurement of histidine modification and radioactive incorporation using a radiolabelled reagent indicated little modification of other amino acids. Modification of this easily modifiable histidine was associated with loss of the enzymes ability to form the active state. With time, the modification reversed and the ability to form the active mixed valence state was recovered. However the reversal of histidine modification observed spectrophotometrically was not matched by loss of radioactivity and a slow transfer of the ethoxyformyl group to another amino acid is proposed. The presence of CN- bound to the active peroxidatic site of the enzyme completely protected the essential histidine from modification. In its active form cytochrome c peroxidase is a dimer, with Ca2+ situated at the interface between the two monomers. Under conditions where the dimer is the dominant species modification of only 0.5 mol histidine abolishes enzyme activity. Limited subtilisin treatment of the native enzyme resulted in cleavage at a single peptide bond. Although the two fragments remain tightly associated, the cleaved enzyme is inactive. Modification with radiolabelled diethylpyrocarbonate and subsequent subtilisin treatment, followed by tryptic digestion of a 9k fragment, showed that radioactivity was located in a peptide containing a single histidine 275. With the benefit of four homologous sequences and the use of secondary structure prediction analysis we can determine that histidine 275 is indeed conserved in the four sequences and is preceded by a remarkably unvaried α-helical region suggestive of functional importance. It is proposed that this conserved residue acts as both a catalytic active site residue and a conduit for intermolecular electron transfer in the active mixed-valence high spin-state.
20
Fujimori, Ko. "Studies on the Histidine Biosynthesis in Arabidopsis thaliana." Kyoto University, 1999. http://hdl.handle.net/2433/157129.
Full textAbstract:
本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものであるKyoto University (京都大学)
0048
新制・論文博士
博士(農学)
乙第10046号
論農博第2216号
新制||農||774(附属図書館)
学位論文||H11||N3232(農学部図書室)
UT51-99-D250
(主査)教授 關谷 次郎, 教授 天知 輝夫, 教授 佐藤 文彦
学位規則第4条第2項該当
21
Chen, Shan. "Histidine-Rich Ca Binding Protein and Cardiac Functions." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1242973363.
Full text
22
Nourbakhsh, Aida. "Molecular Characterization of Inositol Monophosphatase Like Enzymes in Arabidopsis thaliana." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/38695.
Full textAbstract:
myo-Inositol synthesis and catabolism are crucial in many multicellular eukaryotes for production of phosphatidylinositol and inositol phosphate signaling molecules. myo-inositol monophosphatase (IMP) is a major enzyme required for the synthesis of myo-inositol and breakdown of inositol (1,4,5)-trisphosphate (InsP3), a potent second messenger involved in many biological activities. Arabidopsis contains a single canonical IMP gene, which was previously shown in our lab to encode a bifuntional enzyme with both IMP and L-galactose 1-phosphatase activity. Analysis of metabolite levels in imp mutants showed only slight modifications with less myo-inositol and ascorbate accumulation in these mutants. This result suggests the presence of other functional IMP enzymes in plants. Two other genes in Arabidopsis encode chloroplast proteins, which we have classified as IMP-like (IMPL), because of their greater homology to the prokaryotic IMPs such as the SuhB, and CysQ proteins. Prokaryotic IMP enzymes are known to dephosphorylate D-Inositol 1-P (D-Ins 1-P) and other substrates in vitro, however their in vivo substrates are not characterized. A recent study revealed the ability of IMPL2 to complement a bacterial histidinol 1-phosphate phosphatase mutant defective in histidine synthesis, which suggested an important role for IMPL2 in amino acid synthesis. The research presented here focuses on the characterization of IMPL functional roles in plant growth and development. To accomplish this I performed kinetic comparisons of the Arabidopsis recombinant IMPL1 and IMPL2 enzymes with various inositol phosphate substrates and with L-histidinol 1-phosphate, respectively. The data supports that IMPL2 gene encodes an active histidinol 1-phosphate phosphatase enzyme in contrast to the IMPL1 enzyme which has the ability to hydrolyze D-Ins 1-P substrate and may be involved in the recycling of inositol from the second messenger, InsP3. Analysis of metabolite levels in impl2 mutant plants reveals that impl2 mutant growth is impacted by alterations in the histidine biosynthesis pathway. Together these data solidify the catalytic role of IMPL2 in histidine synthesis in plants and highlight its importance in plant growth and development.
âPh. D.
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Pitchairnani, K. "Nuclear Behaviour In Heterokaryons : Genetic And Molecular Analysis Of (his-3+ his-3+) Heterokaryons Of Neurospora Crassa." Thesis, Indian Institute of Science, 2000. https://etd.iisc.ac.in/handle/2005/171.
Full textAbstract:
In contrast to plant and animal cells, the fungal cells are multinucleate. A consequence of their multinucleate condition is heterokaryosis — the occurrence of genetically different nuclei in a common cytoplasm. In nature this condition occurs because of spontaneous mutations in the haploid nuclei in the coenocytic mycelium. Inspite of heterokaryosis being a fundamental aspect of fungal biology, the behaviour and dynamics of nuclei in fungal mycelium are little understood. This study was prompted by the following questions: (1) Why does a fungus need so many nuclei? (2) Are they all active simultaneously? (3) Does the proportion of the different nuclear types in fungal mycelium alter in response to change in conditions of growth? (4) Is the activity of an enzyme related to the dose of nuclei containing the encoding gene?
Experimental approach. The approach taken was to generate heterokaryons in which one of the nuclear types carries a mutant allele for a specific enzyme while the other nuclear type carries the functional allele, introduced by transformation. Because in filamentous fungi, the transforming DNA commonly integrates randomly into the chromosomal DNA, the transformants would be genetic 'variants' in which the ratios of transformed to non-transformed nuclei might be controlled differently. The transformants could thus be useful in investigating the relationship between the frequency of transformed nuclei and the activity of encoded enzyme. In addition the transformants might be useful for studying nuclear behaviour. The availability of developmental information, genetic and molecular methodology, and biochemical mutant in Neurospora crassa made this fungus a material of choice for this investigation.
Strain construction. A histidinol dehydrogenase (his-3) mutant strain was used into which an albino colour marker and a biochemical marker, inositoL were introduced by crossing. The latter two markers served as check against possible laboratory contamination. In addition, a gene mem, was introduced into the strain. In the mem genetic background, the strain has a wild-type morphology on agar medium but when grown in liquid shake culture it produces uninucleate microconidia that are useful in estimating nuclear ratio. Protoplasts of a constructed strain (his-3 al-1; mem; inl) were transformed with a plasmid containing the wild-type his-3 allele, thereby converting the original strain into a heterokaryotic strain having a mixture of transformed (his-3+t) and untransformed (his-3) nuclei. [The superscript +/ is used here to denote an his~3+ allele ectopically introduced by transformation]. Integration of plasmid DNA sequence in three selected transformants, 2T5, 3T3 and 4T12, was confirmed by genomic Southern analysis using the vector DNA as probe. The exponential growth rate of all three transformants was similar (~0.08mgh"1).
Nuclear ratio. Assuming a uniform distribution of nuclei in mycelium, and a correspondence between nuclear ratio in mycelium and conidia, the ratio his-3* {: his-3 was estimated by plating microconidia. In transformant 3T3, the nuclear ratio was 7:1. In 2T5, all nuclei were his-3n. Transformant 4T12 did not produce microconidia. The nuclear ratio in this transformant was therefore estimated by macroconidial plating and found to be 1:5, in favour of his-3 nuclei.
Behaviour of transformants in vegetative and sexual phase. Although the transformants had originally been selected for the expression of his-3+T gene, a majority of macroconidia produced in cultures of 3T3 and 2T5 required histidine to trigger their germination. This condition, referred to as cphenotypic lag', led to a gross underestimation of the proportion of prototrophic macroconidia by the direct plating method and biased the estimation of nuclear ratios. Therefore nuclear ratio was estimated by first germinating macroconidia on histidine supplemented medium before testing colonies in histidine dropout slants and comparing the numbers of auxotrophic and prototrophic mycelia. Phenotypic lag was not observed in 4T12. The variation in the degree of expression of phenotypic lag among the transformants was ascribed to transgene position effect. The transformants differed also in meiotic instability of the transforming DNA — the transforming DNA in 3T3 was passed through unchanged but it was deleted or modified in4T12and2T5.
Experimental alteration of nuclear ratio. The transformants differed with respect to the self-adjusted ratio of transformed to non-transformed nuclei and also to the degree to which their nuclear ratio could be altered by nutritional manipulation of the growth medium, i.e., by growing the transformants in the presence or absence of histidine in the medium. In 3T3, the proportion of his-3+t nuclei progressively decreased by 3.5-fold in the sixth subculture on histidine medium. The change in 4T12 was even more striking: in the sixth serial subculture, the proportion of his-3+t nuclei decreased from 17-20% to -0.05%.However, when it was propagated again in medium that lacked histidine, the frequency of his-3+t nuclei was immediately restored to original level (-17%). That drastic alterations in nuclear ratio occurred upon nutritional manipulation was verified by Southern analysis. The intensity of signal specific for transformed DNA (nuclei) in cultures grown without histidine supplement was strong, but barely detectable in cultures grown with histidine. The signal reappeared when 4T12 was propagated in medium lacking histidine. Histidine induced change in nuclear ratio in 4T12 was further confirmed by three tests: (i) inoculum test using conidia, (ii) hyphal tip analysis, and (iii) genetic test using colour markers.
Nuclear ratio and enzyme activity. Because in 4T12 changes in nuclear ratio could be manipulated, this transformant was used to investigate whether the proportion of his-3+t nuclei is correlated with the levels of encoded enzyme, histidinol dehydrogenase. Surprisingly, the specific activity of histidinol dehydrogenase was the same regardless of the percentage of his-3+t nuclei. This observation suggested that the physiological demand of a metabolite may be satisfied with only a few nuclei carrying the relevant gene. Or in other words the majority of nuclei in the coenocytic mycelium may, perhaps, not be active simultaneously.
Silencing of transforming DNA in nuclei. Two experiments were done to test the possibility that in a majority of nuclei, the transforming DNA is selectively silenced by methylation of cytosine: (1) Southern analysis of chromosomal DNA digested with isoschizomers, and (2) Reactivation by growth of transformants in presence of 5-azacytidine, an inhibitor of methylation. The results suggested that a majority of transformed nuclei may, perhaps, be inactive. The results of Northern analysis suggested that the amount of his-3+t transcript was correlated (but 5-azacytidine experiment
indicated that only few his-3+t nuclei may be active) with the proportion of his-3+t nuclei, but not histidinol dehydrogenase activity. The above results suggested that expression of his-3+t gene was controlled both at the levels of transcription and posttranscription.
Nuclear selection. To study competition between nuclei containing mutant (his-3) nuclei and prototrophic nuclei containing his-3+ gene at its normal chromosomal location or at the ectopic location, heterokaryons were synthesized using strains in which the nuclear types had been marked by non-allelic genetic colour markers, al-1 and al-2. The results suggested that in heteronuclear mixture, the replication rate of the transformed nuclei is affected as compared to the nuclei having the gene in normal chromosomal location.
Major contributions. This study generated (his-3 + his-3+) heterokaryons by transformation. The behaviour of transformants differed in some respects both in the vegetative and sexual phases. It was demonstrated that nuclear ratio could be experimentally altered. However, there was no correlation between nuclear ratio and enzyme activity. The observations imply asynchronous division rate among nuclei and raise the possibility that not all nuclei in the coenocytic mycelium are active simultaneously.
24
Pitchairnani, K. "Nuclear Behaviour In Heterokaryons : Genetic And Molecular Analysis Of (his-3+ his-3+) Heterokaryons Of Neurospora Crassa." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/171.
Full textAbstract:
In contrast to plant and animal cells, the fungal cells are multinucleate. A consequence of their multinucleate condition is heterokaryosis — the occurrence of genetically different nuclei in a common cytoplasm. In nature this condition occurs because of spontaneous mutations in the haploid nuclei in the coenocytic mycelium. Inspite of heterokaryosis being a fundamental aspect of fungal biology, the behaviour and dynamics of nuclei in fungal mycelium are little understood. This study was prompted by the following questions: (1) Why does a fungus need so many nuclei? (2) Are they all active simultaneously? (3) Does the proportion of the different nuclear types in fungal mycelium alter in response to change in conditions of growth? (4) Is the activity of an enzyme related to the dose of nuclei containing the encoding gene?
Experimental approach. The approach taken was to generate heterokaryons in which one of the nuclear types carries a mutant allele for a specific enzyme while the other nuclear type carries the functional allele, introduced by transformation. Because in filamentous fungi, the transforming DNA commonly integrates randomly into the chromosomal DNA, the transformants would be genetic 'variants' in which the ratios of transformed to non-transformed nuclei might be controlled differently. The transformants could thus be useful in investigating the relationship between the frequency of transformed nuclei and the activity of encoded enzyme. In addition the transformants might be useful for studying nuclear behaviour. The availability of developmental information, genetic and molecular methodology, and biochemical mutant in Neurospora crassa made this fungus a material of choice for this investigation.
Strain construction. A histidinol dehydrogenase (his-3) mutant strain was used into which an albino colour marker and a biochemical marker, inositoL were introduced by crossing. The latter two markers served as check against possible laboratory contamination. In addition, a gene mem, was introduced into the strain. In the mem genetic background, the strain has a wild-type morphology on agar medium but when grown in liquid shake culture it produces uninucleate microconidia that are useful in estimating nuclear ratio. Protoplasts of a constructed strain (his-3 al-1; mem; inl) were transformed with a plasmid containing the wild-type his-3 allele, thereby converting the original strain into a heterokaryotic strain having a mixture of transformed (his-3+t) and untransformed (his-3) nuclei. [The superscript +/ is used here to denote an his~3+ allele ectopically introduced by transformation]. Integration of plasmid DNA sequence in three selected transformants, 2T5, 3T3 and 4T12, was confirmed by genomic Southern analysis using the vector DNA as probe. The exponential growth rate of all three transformants was similar (~0.08mgh"1).
Nuclear ratio. Assuming a uniform distribution of nuclei in mycelium, and a correspondence between nuclear ratio in mycelium and conidia, the ratio his-3* {: his-3 was estimated by plating microconidia. In transformant 3T3, the nuclear ratio was 7:1. In 2T5, all nuclei were his-3n. Transformant 4T12 did not produce microconidia. The nuclear ratio in this transformant was therefore estimated by macroconidial plating and found to be 1:5, in favour of his-3 nuclei.
Behaviour of transformants in vegetative and sexual phase. Although the transformants had originally been selected for the expression of his-3+T gene, a majority of macroconidia produced in cultures of 3T3 and 2T5 required histidine to trigger their germination. This condition, referred to as cphenotypic lag', led to a gross underestimation of the proportion of prototrophic macroconidia by the direct plating method and biased the estimation of nuclear ratios. Therefore nuclear ratio was estimated by first germinating macroconidia on histidine supplemented medium before testing colonies in histidine dropout slants and comparing the numbers of auxotrophic and prototrophic mycelia. Phenotypic lag was not observed in 4T12. The variation in the degree of expression of phenotypic lag among the transformants was ascribed to transgene position effect. The transformants differed also in meiotic instability of the transforming DNA — the transforming DNA in 3T3 was passed through unchanged but it was deleted or modified in4T12and2T5.
Experimental alteration of nuclear ratio. The transformants differed with respect to the self-adjusted ratio of transformed to non-transformed nuclei and also to the degree to which their nuclear ratio could be altered by nutritional manipulation of the growth medium, i.e., by growing the transformants in the presence or absence of histidine in the medium. In 3T3, the proportion of his-3+t nuclei progressively decreased by 3.5-fold in the sixth subculture on histidine medium. The change in 4T12 was even more striking: in the sixth serial subculture, the proportion of his-3+t nuclei decreased from 17-20% to -0.05%.However, when it was propagated again in medium that lacked histidine, the frequency of his-3+t nuclei was immediately restored to original level (-17%). That drastic alterations in nuclear ratio occurred upon nutritional manipulation was verified by Southern analysis. The intensity of signal specific for transformed DNA (nuclei) in cultures grown without histidine supplement was strong, but barely detectable in cultures grown with histidine. The signal reappeared when 4T12 was propagated in medium lacking histidine. Histidine induced change in nuclear ratio in 4T12 was further confirmed by three tests: (i) inoculum test using conidia, (ii) hyphal tip analysis, and (iii) genetic test using colour markers.
Nuclear ratio and enzyme activity. Because in 4T12 changes in nuclear ratio could be manipulated, this transformant was used to investigate whether the proportion of his-3+t nuclei is correlated with the levels of encoded enzyme, histidinol dehydrogenase. Surprisingly, the specific activity of histidinol dehydrogenase was the same regardless of the percentage of his-3+t nuclei. This observation suggested that the physiological demand of a metabolite may be satisfied with only a few nuclei carrying the relevant gene. Or in other words the majority of nuclei in the coenocytic mycelium may, perhaps, not be active simultaneously.
Silencing of transforming DNA in nuclei. Two experiments were done to test the possibility that in a majority of nuclei, the transforming DNA is selectively silenced by methylation of cytosine: (1) Southern analysis of chromosomal DNA digested with isoschizomers, and (2) Reactivation by growth of transformants in presence of 5-azacytidine, an inhibitor of methylation. The results suggested that a majority of transformed nuclei may, perhaps, be inactive. The results of Northern analysis suggested that the amount of his-3+t transcript was correlated (but 5-azacytidine experiment
indicated that only few his-3+t nuclei may be active) with the proportion of his-3+t nuclei, but not histidinol dehydrogenase activity. The above results suggested that expression of his-3+t gene was controlled both at the levels of transcription and posttranscription.
Nuclear selection. To study competition between nuclei containing mutant (his-3) nuclei and prototrophic nuclei containing his-3+ gene at its normal chromosomal location or at the ectopic location, heterokaryons were synthesized using strains in which the nuclear types had been marked by non-allelic genetic colour markers, al-1 and al-2. The results suggested that in heteronuclear mixture, the replication rate of the transformed nuclei is affected as compared to the nuclei having the gene in normal chromosomal location.
Major contributions. This study generated (his-3 + his-3+) heterokaryons by transformation. The behaviour of transformants differed in some respects both in the vegetative and sexual phases. It was demonstrated that nuclear ratio could be experimentally altered. However, there was no correlation between nuclear ratio and enzyme activity. The observations imply asynchronous division rate among nuclei and raise the possibility that not all nuclei in the coenocytic mycelium are active simultaneously.
25
Khanna, Rajesh. "L-Histidine ammonia-lyase immobilized by microencapsulation within artifiical cells : enzyme kinetics, stability, and in vitro simulation of histidine depletion for histodinemia." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59405.
Full textAbstract:
L-histidine ammonia-lyase (histidase) was encapsulated within cellulose nitrate artificial cells, and its kinetic parameters were evaluated. Microencapsulated histidase had an apparent activity of approximately 50% of the activity of histidase in solution. Encapsulation did not alter the K$ sb{ rm M}$ of histidase. The K$ sb{ rm M}$ of histidase solution and the K$ sb{ rm M}$ apparent of microencapsulated histidase were both 20mM. Encapsulation of histidase resulted in increased stability of enzymatic activity of storage temperatures of 4$ sp circ$C and 37$ sp circ$C. At 37$ sp circ$C histidase solution reached 50% of its original activity after 9.5 days of storage, while microencapsulated histidase reached the same level after 15 days. At 4$ sp circ$C histidase solution had 63% of its original activity after 21 days of storage, while encapsulated histidase had 95%. In vitro experiments to evaluate the feasibility of microencapsulated histidase for possible experimental therapy in histidinemia were carried out. These experiments evaluated the effectiveness of encapsulated histidase in depleting histidine. Three different volume ratios of histidase loaded artificial cells to substrate solution were tested. A ratio of 1:100 allowed 25% histidine depletion after 120 hours. A 1:50 ratio allowed 35% histidine depletion after 72 hours. A 1:25 ratio allowed 40% histidine depletion after 24 hours.
26
Tusell, Jose Ramon. "Computation of tryptophan fluorescence quenching by amide and histidine." Diss., Montana State University, 2011. http://etd.lib.montana.edu/etd/2011/tusell/TusellJ1211.pdf.
Full textAbstract:
Tryptophan fluorescence quantum yield is widely used to follow protein folding for the villin headpiece subdomain (HP-35) and a synthetic peptide Ac-W-(A) ₃ -H + -NH ₂ (WH5). These biopolymers have a histidine residue, which is a potent quencher of tryptophan fluorescence, positioned four amino acids away from tryptophan. Experiments assumed that when folding occurs the fluorescence of tryptophan will be quenched by histidine due to the formation of an alpha helix. The reliability of folding and unfolding rate constants determined by tryptophan fluorescence has been called into question by several computational studies. A method to calculate the electron transfer matrix element was developed for different donor/acceptor systems. This method shows that the electron transfer matrix element is sensitive to orientation at close distances and that it does not follow a simple exponential decay with distance. This thesis improved the methods developed by Callis and coworker by conducting 100 ns long simulations for single tryptophan proteins and by modifying the calculation of the fluorescence quantum yield to account for heterogeneity in the calculated electron transfer rates. In addition the method was extended to calculate electron transfer rate constants for histidine quenching by conducting 1microsecond long simulations of HP-35 and WH5. Calculated tryptophan fluorescence quantum yields for the single tryptophan proteins show better agreement with experiment than was previously reported. Simulations for HP-35 and WH5 indicate that the ability of histidine to quench the fluorescence of tryptophan is surprisingly controlled by the energy gap dependence on the distance that separates them. The energy gap dependence on this distance arises from water solvation around histidine. At large distances this solvation decreases the ability of histidine to accept an electron from tryptophan. Different tryptophan/histidine rotamers control this distance. Even when HP-35 is completely folded much of the time histidine does not quench tryptophan fluorescence contrary to the idea that histidine is only close when HP-35 is folded. The calculated fluorescence quantum yield is sensitive to the distribution of close and far conformations and the rate of exchange between these two conformations. This sensitivity gives credibility to the folding/unfolding rates derived from tryptophan fluorescence quantum yields.
27
Chen, Zuxu. "Distal Histidine Conformational Flexibility in Dehaloperoxidase from Amphitrite Ornata." NCSU, 2008. http://www.lib.ncsu.edu/theses/available/etd-08192008-155102/.
Full textAbstract:
The enzyme dehaloperoxidase (DHP) from the terebellid polychaete Amphitrite ornata is a heme protein, which has a globin fold, but can function as both a hemoglobin and a peroxidase. As a peroxidase, DHP is capable of converting para-halogenated phenols to the corresponding quinones in the presence of hydrogen peroxide. As a hemoglobin, DHP cycles between the oxy and deoxy states as it reversibly binds oxygen for storage. Herein, we report that the distal histidine shows a large conformational flexibility in the deoxy form. Crystals of deoxy ferrous DHP were obtained by reducing the ferric wild-type DHP in sodium dithionite solution and the structure was determined at 100K to a resolution of 1.22Ã. The heme iron in the deoxy ferrous DHP is five-coordinate and has an out-of-plane displacement of 0.23 Ã for the heme iron relative to the oxy form. The distal histidine, H55 is observed in conformations, which are analogous to the open and closed forms of myoglobin. In the closed conformation, H55 is located inside the distal pocket, but does not penetrate as deeply into the distal pocket as in the metaquo ferric or oxy ferrous structures. This observation is consistent with the hypothesis that H55 interacts with heme iron ligands through hydrogen bonding in the closed conformation. There are two open or solvent-exposed conformations, in which H55 is more than 9.5 Ã away from the heme. The comparison of the deoxy structure with the other structures provides new insight into the correlation between the heme iron ligation and the conformation of distal histidine in the DHP.
28
Livingstone, Emma Kathrine. "Allosteric Regulation of the First Enzyme in Histidine Biosynthesis." Thesis, University of Canterbury. Chemistry, 2015. http://hdl.handle.net/10092/10470.
Full textAbstract:
The ATP-PRTase enzyme catalyses the first committed step of histidine biosynthesis in archaea, bacteria, fungi and plants.1 As the catalyst of an energetically expensive pathway, ATP-PRTase is subject to a sophisticated, multilevel regulatory system.2 There are two families of this enzyme, the long form (HisGL) and the short form (HisGS) that differ in their molecular architecture. A single HisGL chain comprises three domains. Domains I and II house the active site of HisGL while domain III, a regulatory domain, forms the binding site for histidine as an allosteric inhibitor. The long form ATP-PRTase adopts a homo-hexameric quaternary structure.3,4 HisGS comprises a similar catalytic core to HisGL but is devoid of the regulatory domain and associates with a second protein, HisZ, to form a hetero-octameric assembly.5
This thesis explores the allosteric regulation of the short form ATP-PRTase, as well as the functional and evolutionary relationship between the two families. New insight into the mode allosteric inhibition of the short form ATP-PRTase from Lactococcus lactis is reported in chapter two. A conformational change upon histidine binding was revealed by small angle X-ray scattering, illuminating a potential mechanism for the allosteric inhibition of the enzyme. Additionally, characterisation of histidine binding to HisZ by isothermal titration calorimetry, in the presence and absence of HisGS, provided evidence toward the location of the functional allosteric binding site within the HisZ subunit.
Chapter three details the extensive effort towards the purification of the short form ATP-PRTase from Neisseria menigitidis, the causative agent of bacterial meningitis. This enzyme is of particular interest as a potential target for novel, potent inhibitors to combat this disease. The attempts to purify the long form ATP-PRTase from E. coli, in order to clarify earlier research on the functional multimeric state of the enzyme, are also discussed.
Chapter four reports the investigation of a third ATP-PRTase sequence architecture, in which hisZ and hisGS comprise a single open reading frame, forming a putative fusion enzyme. The engineering of two covalent linkers between HisZ and HisGS from L. lactis and the transfer of the regulatory domain from HisGL to HisGS, is also discussed, in an attempt to delineate the evolutionary pathway of the ATP-PRTase enzymes. Finally, the in vivo activity of each functional and putative ATP-PRTase was assessed by E. coli BW25113∆hisG complementation assays.
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Campbell, Samantha Alison. "The second enzyme of histidine biosynthesis from Arabidopsis thaliana." Thesis, University of Glasgow, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325254.
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Yiangou, Yiangos. "Studies on peptide-histidine isoleucine (PHI-27)-like peptides." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47318.
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Pan, Wenlin. "Kinetic Study of Histidine Kinase CheA in Bacterial Chemotaxis." Thesis, University of Missouri - Columbia, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=13877159.
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Histidine kinase CheA is central to signaling in bacterial chemotaxis. This kinase is responsible for the phosphorylation of two response regulators, CheY and CheB. CheY controls flagellar rotation and thus motility. CheB is crucial for sensory adaptation. CheA is dramatically activated, up to 1000-fold, and put under the control of chemoreceptors by formation of the signaling complex. As measured by phosphorylation of CheY, this control modulates the activity of CheA in a range as wide as two orders of magnitude. This change in the activity of CheA is the essence of chemotactic signaling. However, the enzymatic properties altered by kinase incorporation into signaling complexes, chemoreceptor ligand binding or receptor adaptational modification are largely undefined. This dissertation describes the kinetic analysis of kinase CheA. Data are fit to the Michaelis-Menten equation, from which important parameters KM and kcat are obtained. Based on these parameters for CheA at different signaling conditions, important observations and conclusions are made to contribute to better understanding of the control of the activity of kinase CheA, thus the bacterial chemotaxis signaling system.
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Kuo, Wen-Hui Kevin. "Detagging strategies for intensifying poly-histidine tagged protein processing." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609633.
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Hanissian, Silvia H. "Modulation of brain opioid receptors by zinc and histidine /." The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487596807821341.
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Larsen, Andrew. "Growth Studies of the Copper Sensing Histidine Kinase, Cuss." Thesis, The University of Arizona, 2011. http://hdl.handle.net/10150/144570.
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Cochet, Sylvie. "Préparation d'un nouvel échangeur de cations performant et application à la purification automatisée de l'histidine rich glycoprotein plasmatique humaine." Rouen, 1991. http://www.theses.fr/1991ROUEA005.
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Huang, Feijuan, and 黄飞娟. "The histidine-rich proteins in prokaryotes and their biological significance." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/209759.
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Special stretches of sequence with low complexity, highly rich in one certain residue, such as glutamine, asparagines, glutamic acid and histidine, to fulfill certain unique functions, are defined as single-residue-rich sequence (SRRs). Increasing SRRs containing proteins have recently been characterized and some of them have been indentified to be associated with immune system diseases or neuro-degenerative. A systematic and comprehensive analysis on the relationship between the occurrence of histidine-rich motifs (HRMs) and the functions of corresponding proteins have been overlooked.
In this thesis, proteome sequences of 675 prokaryotes including 50 archeae proteome sequences and 625 bacteria were examined and analyzed for HRMs. The HRMs are shown to be extensively distributed in prokaryotic proteomes and the majority (62%) of them is identified to be involved in metal homeostasis. Intriguingly, HRMs are essentially absent from obligate intracellular pathogenic species such as Rickettsiales, Chlamydiae and Tenericutes but are frequently found in the proteomes of Rhizobiales and Burkholderiales, both of which habitat in soils, indicative of environmental habitat-related occurrence of HRMs. Based on the primary sequence to explore the histidine-rich proteins, the present approach could be extended to apply for searching other single-residue-rich proteins, which may shed lights on gaining a further understanding about relationship between the proteins’ sequences and their functions.
A novel group of globally histidine-rich proteins was discovered, among which a histidine-rich protein, bacterioferritin-associated ferredoxin ((BFD)-like [2Fe-2S]) protein from Rhodopseudomonas Palustris BisB18 (termed as BFD shortly) was digged out. The BFD protein consists of a Fe-S cluster domain (FeSD) at the N-terminus and an extremely histidine-rich domain (HRD) at the C-terminus. The intact protein BFD as well as its histidine-rich domain (HRD) was over-expressed, purified and characterized and the effects of metal binding on BFD and HRD were examined in this work.
The intact protein BFD presents as a 20 mer whereas the HRD protein exists as a monomer in solution. However, the CD spectrum of BFD showed the presence of both α-helix and β-sheet in the structure of BFD. The CD spectrum of HRD demonstrated that an extremely large portion of the structure of HRD was random coils, which indicated that the most of the α-helix and β-sheet predominately were located in the Fe-S cluster domain (FeSD) of BFD. It also indicated that HRD adopted a very flexible conformation, which was in good agreement with the results that obtained from the 2D 1H-15N HSQC spectrum of HRD. Isothermal titration calorimetry and equilibrium dialysis revealed that HRD possessed a large binding capacity to divalent metal ions (up to 9 Ni2+, 5 Zn2+ and 4 Co2+ respectively). The E. coli cells over-expressed with the HRD protein showed a significantly evaluated metal resistance to the toxic Ni and Co ions. The amounts of meals in these cells were determined to be approximate 3-5 fold higher than those in the control groups. These results of HRD taken together suggest the characteristics of common globally histidine-rich proteins.published_or_final_version
Chemistry
Doctoral
Doctor of Philosophy
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Mullangi, Vennela Dr. "Development and Application of Histidine Hydrogen Deuterium Exchange Mass Spectrometry." Cleveland State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=csu1388959354.
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Pluta, Radoslaw 1984. "Structural basis of conjugative DNA transfer mediated by MobM, a prototype of the major relaxase family of Staphylococcus aureus." Doctoral thesis, Universitat Pompeu Fabra, 2014. http://hdl.handle.net/10803/346933.
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MobM relaxase from the promiscuous antibiotic resistance plasmid pMV158 is a prototype of the Mob_Pre/MOBV family of relaxases, the major family of relaxases found in Staphylococcus aureus. Staphylococcal infections cause the highest number of lethal cases among antibiotic-resistant bacterial infections. Relaxases initiate the conjugative DNA transfer, a major route for the antibiotic resistance acquisition in bacteria, by nicking their substrate DNA through formation of a covalent DNA-relaxase adduct and terminate the transfer in the recipient cells by rejoining ends of the linearized plasmid. MobM forms a DNA-histidine adduct, unique to MOBV relaxases, instead of a DNA-tyrosine adduct, thus representing a distinct category of relaxases with specialization towards the transfer of short mobile genetic elements in Gram-positive pathogenic bacteria. MobM overall fold resembles the fold of other structurally characterized relaxases, although some important structural differences are present. Molecular basis for the MobM processing of plasmid origin of transfer and active site mechanism are described herein.La relaxasa MobM del promiscuo plásmido de resistencia a antibióticos pMV158 es un prototipo de la familia Mob_Pre/MOBV de relaxasas, la mayor familia de relaxasas se encuentran en Staphylococcu aureus. Las infecciones por estafilococos causan el mayor número de casos mortales entre las infecciones bacterianas resistentes a los antibióticos. Relaxases iniciar la transferencia conjugativa de ADN, una ruta el más frecuente para la adquisición de resistencia a antibióticos por bacterias, por mellar su ADN sustrato mediante la formación de un aducto covalente de ADN-relaxasa y terminan la transferencia en las células receptoras por reincorporarse extremos del plásmido linealizado. MobM forma un aducto de ADN-histidina, único para MOBV relaxases, en lugar de un aducto de ADN-tirosina, lo que representa una categoría distinta de relaxases con especialización hacia la transferencia de elementos genéticos móviles cortos en bacterias patógenas Gram-positivas. MobM estructura general se asemeja a la de otras veces relaxases caracterizan estructuralmente, aunque algunas diferencias estructurales importantes están presentes. Base molecular para el procesamiento de origen del plásmido por MobM y mecanismo de sitio activo se describe en esta thesis.
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Fuchs, R. S. "The purification and characterisation of histidine ammonia-lyase from Klebsiella aerogenes." Thesis, University of Leeds, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384495.
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White, Colleen A. "An investigation into human serum carnosinase." Thesis, Glasgow Caledonian University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301471.
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Lee, Chunsik. "Molecular Mechanisms of Action of Histidine-rich Glycoprotein in Angiogenesis Inhibition." Doctoral thesis, Uppsala University, Department of Genetics and Pathology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7217.
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Angiogenesis, de novo synthesis of blood vessels from the pre-existing vasculature, is required both during embryonic development and in pathophysiological conditions. In particular, tumor growth needs new capillary vessels in order to both deliver oxygen and nutrients and to remove toxin and metabolites. Growth of most solid tumors would be restricted to a microscopic size in the absence of neovascularization. Angiogenesis ensues as a result of a shift in the balance between pro- and anti-angiogenic molecules.
Histidine-rich glycoprotein (HRGP) is a heparin-binding plasma protein. We showed that HRGP inhibits endothelial cell migration and adhesion to vitronectin. As a consequence, HRGP attenuates growth and vascularization of mouse model tumors. The anti-angiogenic effect of HRGP is mediated by the central histidine/proline (His/Pro)-rich domain, which must be released from the parent molecule to exert its effect. A 35-amino acid residue peptide denoted HRGP330, derived from the His/Pro-rich domain, was identified as a minimal active anti-angiogenic domain of HRGP. HRGP330 induces disruption of molecular interactions required for cell motility, such as the integrin-linked kinase/paxillin complex. Moreover, HRGP330 inhibits VEGF-induced tyrosine phosphorylation of α-actinin, a focal adhesion kinase (FAK) substrate. Consequently, the motility of endothelial cells is arrested. By use of a signal transduction antibody array, we identified FAK, paxillin and growth factor receptor-bound 2 (Grb2) as tyrosine phosphorylated in HRGP330-treated cells. We confirmed that HRGP targets focal adhesions in endothelial cells, thereby disrupting the cytoskeletal organization and the ability of endothelial cells to assemble into vessel structures. A critical role of FAK in HRGP-inhibition of angiogenesis was validated using a FAK inhibitor, geldanamycin, which allowed rescue of endothelial cell actin rearrangement.
We identified another potential mechanism in the HRGP/HRGP330 anti-angiogenic effects, exerted through regulation of tumor-associated macrophages (TAMs). HRGP/HRGP330 treatment led to reduced TAM infiltration, which in turn caused a marked decrease in VEGF and MMP-9 levels in the tumor.
Taken together, our present studies show that HRGP/HRGP330 target endothelial cell adhesion, migration, focal adhesions, and furthermore, that HRGP is involved in regulation of macrophage infiltration.
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Thulin, Åsa. "The Role of Histidine-rich Glycoprotein in Angiogenesis and Tumor Growth." Doctoral thesis, Uppsala universitet, Institutionen för medicinsk biokemi och mikrobiologi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-110829.
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Histidine-rich glycoprotein (HRG) is a heparin-binding plasma protein modulating immune, hemostatic and vascular functions. I have studied the antiangiogenic functions of HRG in vitro and in vivo in order to understand the molecular mechanisms of action of HRG as an angiogenesis inhibitor. Angiogenesis is the formation of new blood vessels from the pre-existing vasculature. It is a central rate-limiting step of tumor development and thus a possible target for cancer therapeutics. Previous studies have shown that HRG has antiangiogenic functions in vivo and that the antiangiogenic effects are mediated via the proteolytically released His/Pro-rich domain of HRG. In this thesis we demonstrate that HRG can inhibit endothelial cell migration by interfering with focal adhesion and cytoskeletal turnover. Moreover we have identified the minimal active domain of HRG, a 35 amino acid peptide derived from the histidine- and proline-rich domain of HRG. Analyzing human tumor tissue samples, we have found that a His/Pro-rich fragment of HRG is bound to the vasculature from cancer patients but not to the vasculature from healthy individuals. The fragment is found in association with platelets, and we show that activated platelets can induce a functional microenvironment for the His/Pro-rich fragment. Cancer patients often display an increased coagulation and our data describe a new mechanism to confer specificity of an angiogenesis inhibitor for situations with enhanced platelet activation, as in the tumor. We have further studied the role of HRG in tumor growth by crossing HRG-deficient mice with a transgenic mouse model of pancreatic insulinoma. We show that mice lacking HRG display an elevated “angiogenic switch” and that the total tumor volume is larger in these mice than in wild type mice. HRG is also involved in regulation of platelet function and platelets can stimulate angiogenesis in various ways. We have depleted mice of platelets to study the possible connection between the function of HRG in angiogenesis and platelet regulation. Our data suggest an involvement of platelets in the antiangiogenic activities of HRG.
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Furuta, Kazuyuki. "Regulation of histamine synthesis through post-translational processing of histidine decarboxylase." 京都大学 (Kyoto University), 2006. http://hdl.handle.net/2433/144287.
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Zeng, Yibo, and 曾毅博. "Biophysical characterization hpn-like (HPNL), a histidine- and glutamine-rich protein." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hdl.handle.net/10722/210333.
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Sloane, Rhona Patricia. "Construction, expression, and purification of a histidine-tailed bacteriophage T4 lysozyme." Thesis, University College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243912.
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Stewart, Yvonne Marion. "Function of hybrid histidine kinases in Arabidopsis flagellin-mediated defence responses." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/10669.
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In plants, the first line of microbial recognition relies on the perception of pathogen-associated molecular patterns (PAMPs) allowing plants to detect microorganisms and respond with a set of basal defence responses. The best studied PAMP is flagellin, the main protein component of bacterial flagella. The sensor histidine kinase AHK5 has been shown to play a novel role in mediating flagellin-induced stomatal closure. AHK5 belongs to a family of 9 Arabidopsis hybrid-histidine kinases (HKs). To further investigate the role of such HKs in flagellin-induced signal transduction, physiological responses to the flagellin derived peptide flg22 were examined in available hybrid HK mutant lines. Seedlings of the ethylene insensitive HK ETR1 mutant (etr1-1) showed dramatically reduced flg22 sensitivity as assayed by flg22-mediated seedling growth inhibition. A novel role for the hormone ethylene in flg22-mediated growth inhibition was thus identified. Conversely enhanced sensitivity to low concentrations of flg22 was observed in the AHK2 cytokinin receptor mutant (ahk2-2). However, the absence of flg22-associated growth phenotype in other cytokinin receptor mutants would suggest the role of AHK2 in flg22-mediated seedling growth inhibition may be independent of its role in cytokinin perception. Despite a wild-type sensitivity in aerial plant tissues, distinct flg22-mediated root growth arrest phenotypes were observed in plants defective in the HKs ETR1 and AHK5. Dissection of the mechanisms underlying flg22-mediated root growth inhibition led to the identification of nitric oxide and the ethylene precursor ACC as key secondary messengers. Further characterisation of etr1 mutants showed that, in addition to seedling growth inhibition, ethylene perception is also required for flg22-mediated callose deposition however surprisingly, does not appear to be a requirement for flg22-mediated bacterial immunity. Despite the known requirement for AHK5 in flg22-mediated stomatal closure, flg22-mediated post-invasive bacterial defences were found to be intact in ahk5-1 mutant plants. In summary this study has shown that ethylene perception via the ethylene receptor HK family plays an integral part in flg22-mediated signalling. In addition, organ/tissue specific functions for three of the nine hybrid kinases, AHK2, AHK5 and ETR1 in flg22-mediated signal transduction have been identified.
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Zeng, Yibo. "Biophysical characterization hpn-like (HPNL), a histidine- and glutamine-rich protein." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42841185.
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Lee, Sang Tae Chemistry Faculty of Science UNSW. "Model studies of the cub-histidine-tyrosine centre in cytochrome c oxidase." Awarded by:University of New South Wales. Chemistry, 2005. http://handle.unsw.edu.au/1959.4/33251.
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This thesis reports the synthesis and copper coordination chemistry of covalently-linked aryl-imidazole derivatives designed as models for the crosslinked imidazole-phenol sidechains of the His-Tyr cofactor in the CcO. Three new imidazole- (HL1 - HL3) and three new indole- (HL4 - H2L6) containing tripodal ligands were synthesised. The conjugate addition of an imidazole to activated quinone derivatives was developed as a new route to organic models for the Tyr His cofactor. Two monodentate imidazole-aryl, Im-hq(OH)2 and Im-ArOH, and an imidazole-quinone, Im bq were obtained using this route. The X-ray crystal structure of Im-hq(OH)2.EtOH was determined. The route was also used to give new chelating ligands, H2L10 and HL12, containing a cross-linked imidazole-phenol surrogate for the Tyr244-His240 cofactor. Copper complexes of Im-hq(OH)2, Im-bq, Im-ArOH, H2L10-HL12, and HL1-H2L6 were prepared, and the X-ray crystal structures of [Cu(terpy)(Im-bq)][BF4]2 and five other copper complexes were determined. The physiochemical properties of the copper complexes were characterized by FT-IR, UV-Vis-NIR, EPR and (spectro)electrochemical studies. Key results include: the oxidation of Im-ArO- anion affords the semiquinone radical, Im-sq(4OH)(1O??????), in a hydrous solvent. However, the oxidations of neutral Im-ArOH and [Cu(tpa)(Im-ArOH)]2+ produce the corresponding phenoxy radical species that rapidly and reversibly dimerise to give quinol cyclohexadienone, QCHD, dimers. Significantly [Cu(tpa)(Im-sq(4OH)(1O??????))]2+ was EPR silent, perhaps due to antiferromagnetic coupling between the Cu(II) (S=1/2) and semiquinonyl radical (S=1/2) centres. Deprotonation of the hydroquinone in [Cu(tpa)(Im-hq(OH)2]2+ produces the hydroquinone dianion which reduces the Cu(II) centre. The semiquinone radical is coordinatively labile and dissociates from the Cu(I) centre. The biological implications of these results are mentioned.
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Sitton, N. G. "An investigation into the cause and specificity of low serum histidine in rheumatoid arthritis." Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378869.
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Gibson-Harris, Yvonne C. P. "Studies of the histidine permease of Salmonella typhimurium in Escherichia coli and Methylophilus methylotrophus." Thesis, University of Leicester, 1988. http://hdl.handle.net/2381/33707.
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The broad aim of this project was to investigate the effects of introducing the Histidine permease of S.typhimurium into M.methylotrophus, a Gram negative bacterium with no known protein transport mechanism. This should not only contribute to the elucidation of the mechanism by which these periplasmic permeases operate, but also help in the understanding of M.methylotrophus an organism of commercial importance whose biochemistry is not well characterised. Although the entire operon encoding this permease had recently been sequenced prior to the commencement of this study, the precise identity of the components had not been established; furthermore, since each component is produced in very small amounts, simple identification by electrophoretic techniques was not possible. My initial aim, therefore was to introduce the structural genes of the operon under the control of a strong, but inducible promoter, inorder that each gene product could be identified and the location of the protein within the cell established. The His P protein was identfied in this manner, however discrepencies in overproduction prevented the precise location of this polypeptide within the cell from being established. Induced expression of the hisQ gene also identified an overproduced polypeptide of 30,000 molecular weight, suggesting this to be the His Q protein, however I was unable to establish a precise identification. The construction if these new plasmid vectors assisted in the second stage of this study; the introduction of the histidine permease into M.methylotrophus. Furthermore, with three out of four protein components formally identified in E.coli these could then be confirmed in M.methylotrophus. The results obtained clearly show, not only that at least His J was synthesised, but also apparently processed and localised correctly into the periplasm of M.methylotrophus. Furthermore, the permease system was found to be functional in M.methylotrophus demonstrating active histidine uptake into the cell.