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Preparation of expression construct and purification of xNEIL3 glycosylase
Landová, Barbora ; Obšil, Tomáš (advisor) ; Hlouchová, Klára (referee)
DNA glycosylases are important enzymes responsible for the recognition and removal of base DNA damage. These DNA lesions are formed spontaneously or as an effect of environmental agents. NEIL3 (Endonuklease VIII - like 3) enzyme belongs to a Fpg/Nei family of glycosylases implicated in the DNA repair of oxidative bases, abasic sites. Recently, it has been shown that these enzymes are capable of removal of one type of interstrand crosslink by so unknown repair pathway. Unrepaired DNA crosslinks block DNA replication and may lead to cell death or sever chromosomal damage and later even cancer. This thesis is focused on revealing molecular mechanisms of the interstrand DNA- DNA cross-link repair by NEIL3 glycosylase. (In Czech)
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Selection approaches in directed evolution of binding proteins
Huličiak, Maroš ; Malý, Petr (advisor) ; Hlouchová, Klára (referee)
Artificial binding proteins derived from small protein domains attract attention as a promising alternative to monoclonal antibodies and can be used in many kinds of applications. They are useful in diagnosis of human diseases, seem to be a clue for more efficient vaccine development preventing from global diseases such as AIDS, can exhibit a therapeutic potential or improve purification techniques. For the selection of protein variants with desired properties such as high specificity and binding affinity, more than 10 different selection techniques have been developed. So called display techniques such as phage display, yeast display, retroviral display or baculovirus display are based on protein expression from different vectors. Contrary that, ribosome display, mRNA display and CIS display are cell-free systems based on in vitro translation. Development of different selection approaches allows production of post- translationally glycosylated, phosphorylated and acetylated proteins, increased yield of the produced binders and improved their binding properties. The submitted work provides an overview of current selection techniques, compare their parametres regarding to combinatorial libraries, describes their advantageous properties and limitations, and focus on a practical utilization of...
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The effect of Ca2+ ion on the enzymatic activity of human glutamate carboxypeptidase II
Nedvědová, Jana ; Bařinka, Cyril (advisor) ; Hlouchová, Klára (referee)
Human glutamate carboxypeptidase II (GCPII, EC 3.4.17.24) is a homodimeric membrane glycoprotein. GCPII has been studied as a marker of prostate carcinoma and a therapeutic target of neurodegenerative disorders. The extracellular region of the protein is composed of three domains, apical, protease and C-terminal. There are two zinc ions in the active site that are essential for the enzymatic activity. A calcium ion is located between apical and protease domains near the dimeric interface approximately 20 Å away from the active site. Consequently, the Ca2+ ion in unlikely to participate in substrate hydrolysis. The aim of this thesis is to elucidate the function of Ca2+ in GCPII using a combination of molecular-biological, biochemical and biophysical approaches. To this end we prepared series of GCPII variants with mutations in calcium-coordinating amino acids. The mutant constructs were expressed in insect S2 cells and purified by combination of affinity and size exclusion chromatography. Enzymatic activity and thermostability of the mutants were decreased significantly. Furthermore, mutated proteins were aggregation prone and formed a monomeric GCPII species. Our results thus show that Ca2+ ion plays an essential role in proper GCPII folding as well as the formation of a homodimer molecule that is...
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Cell-free expression of protein libraries made of different amino acid repertoires
Neuwirthová, Tereza ; Hlouchová, Klára (advisor) ; Míšek, Jiří (referee)
This bachelor thesis is an introduction to a project dealing with the influence of genetic code evolution (and the consequentamino acid repertoire in proteins) on the evolution of protein structure and function. The initial amino acid alphabet was apparently only half the size of the present alphabet and according to available metaanalyses it included only about 10 prebiotically present amino acids derived from potential exogenous or endogenous sources. This work includes mRNA transcription and cell-free expression of five randomized protein libraries (containing approximately 1011 variants). These libraries differ in their amino acid composition and reflect individual predicted stages of genetic code evolution. The main goal is to convert libraries from DNA to protein form to provide a source for library purification and their subsequent biophysical (occurrence of secondary and tertiary structure) and functional analyses. The whole research could theoretically contribute to a few basic questions not only in the fields of protein evolution but also in areas of synthetic biology or protein engineering. Keywords: Cell-free expression, proteins, genetic code evolution This thesis is written in Czech.
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Never Born Proteins: Occurence and characterization of secondary structure motifs
Treťjačenko, Vjačeslav ; Hlouchová, Klára (advisor) ; Kopecký, Vladimír (referee)
An experimental study on randomly generated protein sequences can provide important insights into the origin and mechanism of secondary structure formation and protein folding. In this study we bring biophysical characterization of five protein sequences selected from the in silico generated library of random chains. The sequences were selected on the basis of bioinformatic analysis in order to find the candidates with the maximum potential to possess secondary structure. This study shows that the random polypeptide sequences form stable secondary structures and in some show the signs of tertiary structure, such as hydrophobic core formation and distinctive oligomerization pattern. While the work presented in this thesis is work in progress on a larger study, the data already demonstrate that unevolved protein sequence space provides a lot of potential for secondary and tertiary structure formation that awaits its characterization. Powered by TCPDF (www.tcpdf.org)
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Vascular Endothelial Growth Factor Expression and its Application in Vascular Tissue Engineering
Mikulová, Barbora ; Konvalinka, Jan (advisor) ; Hlouchová, Klára (referee)
This paper deals with the expression of vascular endothelial growth factor (vascular endothelial growth factor, VEGF) and its use in tissue engineering of vascular wall. During the work interaction of endothelial cells with the modified fibrin-based biomaterial into which vascular endothelial growth factor (VEGF-A121) has been incorporated was monitored. This modification supported the adhesion and growth of endothelial cells. Vascular endothelial growth factor VEGF-A121 is signal glycoprotein that activates transmembrane receptors on endothelial cells. VEGF-A121 is a key regulator in vasculogenesis, angiogenesis, proliferation, migration and survival of endothelial cells. In this work, this protein was heterologously expressed at a thioredoxin fusion partner in an expression system of E. coli Origami B (DE3). Recombinant VEGF-A121 was additionally coexpressed with bacterial chaperones GroEL/GroES for potential increase of its solubility and biological activity. In the next part of this work thin fibrin network was prepared by catalytic action of thrombin on the polystyrene-bound monolayer of fibrinogen. This network has been further enriched by vascular endothelial growth factor (VEGF-A121), which was covalently incorporated in it by enzyme activity of transglutaminase (factor XIIIa). The last...
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The role of iron in the metabolism of the amoeba Naegleria gruberi
Ženíšková, Kateřina ; Konvalinka, Jan (advisor) ; Hlouchová, Klára (referee)
Iron is a biogenic trace element that is vital for all organisms on the planet Earth. This element occurs in biological systems in the form of Fe3+ and Fe2+. These two forms are often incorporated in heme structures or iron-sulfur clusters. Proteins containing iron ions have a wide range of functions in organisms. The main functions include the transport of electrons in the respiratory chain (Rieske's proteins, cytochromes), DNA synthesis (ribonucleotide reductase) and the participation in the Krebs' cycle (aconitase, succinate dehydrogenase). Naegleria gruberi is a nonpathogenic amoeba known for its pathogenic relative Naegleria fowleri. This organism causes the primary amoebic meningoencephalitis. An interesting fact about Naegleria gruberi genome is that it contains genes for both aerobic and anaerobic metabolisms. The purpose of my bachelor work was to investigate the effect of availability of iron ions on metabolism in Naegleria gruberi. Changes in the activities of enzymes from different metabolic pathways were studied including lactate dehydrogenase, isocitrate dehydrogenase, Fe- hydrogenase, aconitase and fumarase. The most significant changes were observed in the activities of alcohol dehydrogenase and Fe-hydrogenase. Key words: Iron, heme, iron-sulfur clusters, availability of iron ions,...
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Expression and characterization of selected never-born proteins
Šimonová, Johana ; Hlouchová, Klára (advisor) ; Pavlíček, Jiří (referee)
This bachelor thesis deals with the study of random polypeptide sequences and occurence of secondary structure in random sequence space. Sequences for experimental characterization were selected from library containing 104 random sequences on the basis of (i) either predictions of secondary structure and disorder occurence and prediciton of solubility or (ii) a completely random selection. Eight proteins studied in this thesis belong to the second option - i.e. they were selected from the in silico generated library completely randomly. First, expression and solubility was analysed for these eight proteins. In addtion, one of the proteins was selected for further analysis. The thesis involves optimization of its expression and purification as well as its detailed biophysical characterization. (In Czech) Key words: protein evolution, protein structure, random sequences
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LacZ-alpha complementation peptide as a tool for molecular evolution studies
Ptáčková, Barbora ; Hlouchová, Klára (advisor) ; Vaněk, Ondřej (referee)
Proteins are the key structural and functional molecules of living organisms. Although the last decades have brought a lot of knowledge about their structural and functional characteristics, science still lacks very basic answers about how these properties evolved. Current predominant opinions suggest that early genetic code contained only a subset of today's canonical amino acids. Both exogenous and endogenous sources of prebiotic amino acids imply that even though the prebiotic amino acid repertoire was very broad, only about half of the proteinogenic amino acids were present. It follows that the ''evolutionary new'' amino acids were added to the genetic coding system only after the evolution of their biosynthetic pathways. From the current scientific knowledge it is unclear whether proteins composed of "evolutionary old" amino acids could serve basic metabolic functions and if today's proteins could be "reversely-evolved" to be composed of only such a subset of amino acids while maintaining their structural and functional integrity. These questions lie at the core of this study. This thesis aims to test a starting methodology that would randomize "new" amino acid positions by "old" amino acids in the sequence of LacZ-alpha peptide. This peptide was selected as a target model protein because it...
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Preparation of expression vectors for NKp65 and KACL, new members of human NK cell receptor family
Mikulová, Barbora ; Vaněk, Ondřej (advisor) ; Hlouchová, Klára (referee)
Natural killer cells create an important part of innate immune system. Their importance lies in their ability to recognize and kill abnormal cells, especially tumour cells and virally infected ones, without previous activation. To recognize their targets, NK cells use a wide variety of surface receptors, both activating and inhibitory. If a ligand binds to an NK receptor, immune response is triggered. Examples of such ligand-receptor pairs are NKp80-AICL and NKRP1-LLT1 on human lymphocytes. Another ligand-receptor system of this kind is NKp65 and KACL, two recently discovered lectin receptors on human immunocytes. KACL is the last and most recently characterized member of CLEC2 receptor family in humans. Its expression is almost exclusively restricted to skin. NKp65, a close relative of NKp80, is a glycoprotein which stimulates NK92MI cell cytotoxicity upon KACL engagement. NKp65 has been shown to bind to KACL with a fairly high affinity by surface plasmon resonance measurement. This thesis aims at describing the cloning of expression vectors coding for NK cell receptors NKp65 and KACL, expression of these proteins in HEK293T cell line and their purification. Keywords: NKp65, KACL, NK cell, lectin, receptor, plasmid (in Czech)
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