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Development of a fast method for site-directed mutagenesis in Streptococcus zooepidemicus
Černý, Zbyněk ; Španová, Alena (referee) ; Pepeliaev,, Stanislav (advisor)
This diploma thesis is focused on development of a fast method for site-directed gene mutagenesis in Streptococcus zooepidemicus based on the mechanism of natural competence. Several genes were selected based on experimental data which highly probably influence hyaluronic acid synthesis. The deletion of the selected genes from genomic DNA was performed as proof of concept, and the resulting recombinant strains were characterized regarding changes of hyaluronic acid precursor concentrations (glucuronic acid and N-acetylglucosamin) in time of cultivation and the end production of hyaluronic acid.
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Identification of residues of acylated domain of RTX toxins involved in acyltransferase binding
Grobarčíková, Michaela ; Mašín, Jiří (advisor) ; Černý, Ondřej (referee)
Both adenylate cyclase toxin (CyaA) and α-hemolysin (HlyA) are members of Repeats in ToXins (RTX) cytolysins that play key roles in the virulence of Bordetella pertussis and Escherichia coli, respectively. Bacterial RTX toxins represent a growing group of proteins produced by gram- negative bacteria. These pore-forming RTX toxins share several notable common features: (1) they require post-translational activation by attachment of fatty acid chains to two lysine residues; (2) they contain a hydrophobic domain that forms cation-selective pores in target cell membranes; (3) they are secreted by a type I secretion system; (4) after secretion, they become biologically active by binding of Ca2+ to the nonapeptide glycine- and aspartate-rich repeats. CyaA translocates a unique AC enzyme to the cytosol of phagocytes and subverts their bactericidal functions by unregulated conversion of ATP to cAMP. CyaA and HlyA also permeabilize the cell membrane of eukaryotic cells through cation-selective pores. Both toxins preferentially bind to cells expressing β2 integrins but can also interact with a variety of cells that do not express integrins or with naked lipid membranes. Both toxins are activated from protoxin form by post- translational acylation mediated by a specific acyltransferase. CyaA is activated by...
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Role of Arginine 717 in insulin receptor respective Arginine 704 in IGF-1 receptor for the interaction with ligands
Kertisová, Anna ; Selicharová, Irena (advisor) ; Ryšlavá, Helena (referee)
Insulin and insulin-like growth factor 1 (IGF-1) are peptide hormones that are important regulators of cellular metabolism, proliferation and apoptosis. Disruptions in signalling pathways may cause a whole range of diseases from diabetes mellitus type 1 and type 2 to cancer or neurodegenerative diseases. The cellular response to these hormones is mediated by insulin (IR) and IGF-1 receptors (IGF-1R) with a tyrosin-kinase activity. Receptors are created as hetero-tetramers of two extracellular α-subunits and two intracellular β-subunits. Studies of receptor structures try to elucidate the basic principles of the interaction of receptors with their ligands. However, the role of some amino-acid residues in binding remains unclear. It was suggested that the arginine 704 of IGF-1R may interact with Glu58 IGF-1. In comparison with IGF-1R, the equivalent arginine 717 IR was not associated with an important role in insulin binding in previous studies. This thesis is focused on clarifying the role of Arg704 IGF-1R and for comparison analogically on Arg717 IR isoform A (IR-A) in ligand binding to the receptors. Therefore, mutant variants of IGF-1R in positions His697 and Arg704 and variants IR-A in positions His710 and Arg717 were created. The role of histidines 697 IGF-1R and 710 IR was already elucidated...
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Preparation of mutant variants of Kingella kingae RtxA cytotoxin for membrane topology research
Lichvárová, Michaela ; Osičková, Adriana (advisor) ; Malý, Petr (referee)
Kingella kingae is a facultative anaerobic, β-hemolytic, gram-negative bacterium. It has been shown, that K. kingae is an important cause of invasive infections in young children, especially between 6 to 36 months of age. The most common diseases caused by K. kingae are septic arthritis, osteomyelitis, bacteremia and infective endocarditis. The key virulence factor of K. kingae is the secreted RtxA toxin, which belongs to the RTX toxins family (Repeats in ToXin). These are divided into two categories, hemolysins and leukotoxins, based on the cellular specificity of their action. The broad specificity of the RtxA toxin indicates that RtxA can be classified as a cytolytic RTX hemolysin. RtxA molecules are inserted into the host cell membrane and form cation-selective membrane pores that trigger cation flux. This disrupts normal cell physiology and eventually leads to cell lysis. The aim of this bachelor thesis was to prepare mutant variants of the K. kingae RtxA cytotoxin with lysine substitutions in the pore-forming domain for future study of the membrane topology of the toxin using biotin binding to the lysine residues. In order to observe the topology of the RtxA toxin in the host cell membrane, the toxin must be able to insert to the cell membrane. Therefore, another objective was to determine...
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Study of function and molecular architecture of fungal nitrilases applicable in biocatalysis
Veselá, Alicja Barbara ; Martínková, Ludmila (advisor) ; Macek, Tomáš (referee) ; Teisinger, Jan (referee)
Nitrilases are enzymes which catalyze the hydrolysis of a nitrile into the corresponding carboxylic acid and ammonia. These enzymes are potentially applicable in biocatalysis and bioremediation because of their advantages over the conventional (chemical) methods of nitrile hydrolysis (lower demand for energy, safety, simplicity, high yields, selectivity). In this work, genome mining was used to search for the sequences of hypothetical nitrilases from filamentous fungi. The amino acid sequences of previously characterized fungal nitrilases were used as the templates. Then the new synthetic genes together with other genes from our nitrilase library were expressed in E. coli and the substrate specificities of the enzymes thus produced were compared. Significant attention was focused on the relationships between the sequence of the enzyme and its substrate specificity. The arylacetonitrilases from Arthroderma benhamiae (NitAb) and Nectria haematococca (NitNh) were purified and characterized. Their substrate specificities, kinetic parameters, pH and temperature profiles and subunit and holoenzyme size were assessed. NitAb and NitNh together with other recombinant fungal nitrilases were employed in the hydrolysis of high concentrations of (R,S)-mandelonitrile in a batch or fed-batch mode. Nitrilase from...
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Processing peptidases of M16B family and their evolutionary relationships
Hanušová, Iva ; Stiborová, Marie (advisor) ; Šulc, Miroslav (referee)
The theoretical part of this bachelor thesis deals with the group of processing peptidase of the M16B family. The main focus is on the structure and the evolution of mitochondrial and hydrogenosomal processing peptidase and also the hypothetical peptidase from the bacterium Rickettsia prowazekii. In the practical part of this work, the constructs coding the α-subunit of hydrogenosomal processing peptidase (α-HPP) with the substituted tryptophan residue in the position 236 for phenylalanine and tyrosine were prepared using the site-directed mutagenesis. Subsequently, the new reporter tryptophan residue was introduced in α-HPP in positions 256, 260, 267 or 271 in the so-called glycine-rich loop.
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Expression and characterization of recombinant capsid protein from HIV and its mutants: towards inhibition of virus assembly
Sivá, Monika ; Konvalinka, Jan (advisor) ; Maloy Řezáčová, Pavlína (referee)
Human immunodeficiency virus infection has been a threat to the world for the last thirty years. It causes a condition called acquired immunodeficiency syndrome leading to complete collapse of immune system and death if not treated. There are many anti-HIV drugs that are part of the combined antiretroviral treatment but they only slow down the progress of the infection. Although the success of all the 31 antiviral agents is remarkable, the cure is not efficient enough. The research of potencial new HIV drugs is now focusing on new targets of viral inhibition. The capsid protein is a potential target of virion assembly and maturation inhibitors due to its multimerization features. The N-terminal domains of six capsid proteins create hexamers. These are connected to each other by dimers of the C-terminal domains according to X-ray and NMR studies. There are inhibitors that bind to the C-terminal domain, alter its conformation and weaken the protein-protein interaction of the dimer. Protein calorimetry is a method that could detect and quantify protein-protein interactions and thus capsid protein dimerization and its inhibition. We expressed and purified recombinant wild-type capsid protein and its C-terminal domain that both dimerize in solution and crystals. Their dimerization constant was determined by...
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Development of a fast method for site-directed mutagenesis in Streptococcus zooepidemicus
Černý, Zbyněk ; Španová, Alena (referee) ; Pepeliaev,, Stanislav (advisor)
This diploma thesis is focused on development of a fast method for site-directed gene mutagenesis in Streptococcus zooepidemicus based on the mechanism of natural competence. Several genes were selected based on experimental data which highly probably influence hyaluronic acid synthesis. The deletion of the selected genes from genomic DNA was performed as proof of concept, and the resulting recombinant strains were characterized regarding changes of hyaluronic acid precursor concentrations (glucuronic acid and N-acetylglucosamin) in time of cultivation and the end production of hyaluronic acid.
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