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Elucidation of the properties and structure of the pore-forming domain of colicin U produced by bacterium Shigella boydii.
Dolejšová, Tereza ; Fišer, Radovan (advisor) ; Krůšek, Jan (referee) ; Osička, Radim (referee)
Colicin U is a protein produced by bacterium Shigella boydii. It belongs to the group of pore-forming colicins. These colicins interact with receptors in the outer membrane of bacteria closely related to a producing colicinogenic strain. After interaction with the receptor, colicin is translocated across the outer membrane and periplasm to the cytoplasmic membrane where it forms pores. Consequently, the pore formation leads to membrane depolarization and cell death. In this thesis I decided to study the pore-forming properties of colicin U and its membrane topology. It is shown that colicin U pores are formed by only one colicin molecule and they are voltage dependent. Using measurements with nonelectrolytes we estimated a theoretical inner profile of the pore and its inner diameter to be between 0.7 and 1 nm. Above that, a membrane topology of colicin U pore-forming domain (PFD) is studied. BLM measurements with biotinylated colicin U showed that a significant part of colicin's PFD was translocated to the opposite side of the membrane after the pore opening. The segment between substituted amino acids F463 and D486 was evidenced to be on the trans side of the membrane after the pore opening. Additionally, properties of peptide H1, which reflects a significant part of the first α- helix of colicin...
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Structure-function relationship of Kingella kingae RtxA toxin.
Růžičková, Eliška ; Osička, Radim (advisor) ; Šulc, Miroslav (referee)
Kingella kingae is a pediatrically significant, facultative pathogen. It asymptomatically colonizes the oropharynx of young children, where it is a part of the normal microflora. However, if it penetrates the respiratory epithelial barrier and begins to spread throughout the body, it can cause serious infectious diseases. Thanks to today's advanced diagnostic methods, K. kingae is included among important human pathogens, and in pediatric patients, K. kingae is reported as a frequent cause of osteoarticular infections, such as osteomyelitis and septic arthritis, bacteremia, and endocarditis. The key virulence factor of this bacterium, the cytotoxin RtxA, belongs to the RTX (Repeats in ToXin) toxin family. This family of toxins shares several characteristic features: (i) the presence of a hydrophobic pore-forming domain in the N-terminal part of the molecule containing several predicted transmembrane α-helices (ii) the inactive protoxin is activated by different types of fatty acids bound to specific lysine residues in the acylated domain, (iii) the presence of nonapeptide repeat sequences, rich in glycine and aspartate residues, that are important for the binding of calcium ions, (iv) the presence of a C-terminal secretion signal that is recognized by the type I secretion system (T1SS), and (v)...
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Structure and function of RTX toxins of Gram-negative bacteria
Zhuk, Karyna ; Osička, Radim (advisor) ; Šulc, Miroslav (referee)
RTX toxins (Repeats in ToXin) are produced by Gram-negative bacteria, most of which are important human or animal pathogens. The polypeptide chain of each RTX toxin consists of four conserved regions. An N-terminal hydrophobic domain, which is important for insertion of the RTX toxin into the host cell membrane and pore formation. The hydrophobic domain is followed by an acylated segment containing conserved lysine residues, at which the toxin is acylated and thus activated. The C-terminal portion of each RTX toxin contains a repeat domain to which calcium ions bind. The C-terminus of the toxin contains a secretion signal that is recognized by the type I secretion system, which transports the toxin from the bacterial cytosol to the external environment. After secretion, RTX toxins interact with the cell surface via specific β2 integrins and/or glycosylated structures such as glycoproteins and gangliosides or membrane components such as sphingomyelins and cholesterol. Once bound to the cell, RTX toxin monomers insert into the membrane and oligomerize to form pores. The uncontrolled flow of ions through these pores can lead to disruption of bactericidal functions of myeloid phagocytes, stimulation or suppression of the release of pro-inflammatory cytokines, modulation of various signaling and...
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Current approaches in the development of vaccines against infectious viral diseases
Vargová, Soňa ; Malý, Petr (advisor) ; Osička, Radim (referee)
Vaccination remains one of the most successful biomedical interventions for preventing viral diseases. While early vaccines were developed by attenuating the infectious agent in cell cultures or by inactivation, new delivery platforms are on the rise thanks to the advent of genetic engineering. The COVID-19 pandemic stimulated the rapid adoption and a massive deployment of these platforms. Viral vector vaccines elicit antigen expression within cells and induce a robust cytotoxic T cell response, unlike protein subunit vaccines conferring mainly humoral immunity. mRNA vaccines also deliver the antigen inside the cells while offering more manageable and faster manufacturing possibilities. Unlike DNA-based vaccines, mRNA does not enter the nucleus, and thus, the probability of disrupting gene expression in the recipient cell is diminished. This thesis aims to offer an overview of current approaches in vaccinology and discuss the various platforms in use. The thesis will also present recent advances in the development of prophylactic vaccines against infections with human immunodeficiency virus-1 (HIV-1) and hepatitis C virus (HCV) and also will focus on a recently proposed strategy for vaccine development based on non-cognate ligands mimicking epitopes recognised by broadly neutralising antibodies...
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Modulation of interactions of cytokines and their receptors
Kolářová, Lucie ; Schneider, Bohdan (advisor) ; Rozbeský, Daniel (referee) ; Osička, Radim (referee)
Protein-protein interactions and interactions with other molecules including DNA and RNA, play an important role in a range of biological activities and processes in all living cells. Understanding of protein-protein interactions, new approaches, and tools for their modulations are valuable for medicine, biotechnology, and drug development. We used the interleukin-10 family of cytokines as a model system for our research of biological interactions and modulation of their functions. A key prerequisite to study biological processes and a detailed understanding of biomolecular interactions is a recombinant protein that is stable under a broad range of conditions. Recombinant protein expression in sufficient yield and quality is often a challenging task. Therefore, we aimed at developing new approaches in protein design and production. In the first part of our study, we modified IL-24, a member of the IL-10 family to increase its expression and stability. We demonstrated that protein engineering is a powerful tool in research of difficult protein targets. In the second part of our study, we adopted new approaches in designing new protein scaffolds suitable for use in the ribosome and yeast display techniques. Protein scaffolds have become promising alternatives to antibodies in protein drug...
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Molecular epidemiology and characteristics of bacterial pathogens on lung infection in patients with cystic fibrosis
Vošahlíková, Šárka ; Nemec, Alexandr (advisor) ; Melter, Oto (referee) ; Osička, Radim (referee)
Cystic fibrosis is the most abundant inherited autosomal recessive disease in Caucasian population. Cystic fibrosis is caused by a dysfunction of a transport channel which is responsible for the transport of chloride ions on the apical side of the plasma membrane. Despite the fact that the dysfunction of the transport channel is present in several organs, the most severely affected one is the respiratory system. Because of the ion imbalance, thick sticky mucus is produced on the surface of the airways which then prevents the removal of dust particles and bacteria. The main complications of cystic fibrosis are the bacterial infections of the respiratory system which become chronic during the patient's life and thus are the most common causes of the respiratory failure and premature death. The most important agents causing these infections are Pseudomonas aeruginosa and Burkholderia cepacia (Bcc). Infections caused by those bacteria are practically untreatable and serious complications arise from the existence of epidemic strains which can be transfered from patient to patient. Precise and fast diagnostics of pathogenic strains is a critical step to avoid spreading bacterial infections as well as strictly followed anti- epidemic strategies mainly based on isolation of cystic fibrosis patients according to...
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Proteins mimicking epitopes of broadly neutralizing HIV-1 antibodies
Zosinčuková, Tereza ; Malý, Petr (advisor) ; Osička, Radim (referee)
HIV-1 is a dangerous retrovirus which represents one of the world's leading health problems. HIV-1 infection is incurable and without proper treatment by antiretroviral therapy it leads to death within several years. Despite intensive research, no HIV vaccine is currently available. This thesis presents a new and unique approach which has not been used for vaccine development yet. The promising strategy is based on small binding proteins that can elicit broadly neutralizing HIV-1 antibodies by mimicking their epitopes. The aim of this project was to select and characterize small binding proteins that can successfully mimic the surface of viral envelope glycoproteins that is recognized by the broadly neutralizing HIV-1 antibodies PGT121 and PGT126. Proteins were selected from a highly complex combinatorial protein library derived from a new type of scaffold called Myomedin. Firstly, the extent of the protein library was narrowed down using the ribosome display. Then the direct sandwich ELISA screening was applied to select scaffold variants that interact with the target antibodies. In total over 200 variants were tested and several promising candidates were found. These Myomedin variants were purified, biochemically and biophysically characterised and the best ones were used to immunize mice....
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Molecular epidemiology and characteristics of bacterial pathogens on lung infection in patients with cystic fibrosis
Vošahlíková, Šárka ; Nemec, Alexandr (advisor) ; Melter, Oto (referee) ; Osička, Radim (referee)
Cystic fibrosis is the most abundant inherited autosomal recessive disease in Caucasian population. Cystic fibrosis is caused by a dysfunction of a transport channel which is responsible for the transport of chloride ions on the apical side of the plasma membrane. Despite the fact that the dysfunction of the transport channel is present in several organs, the most severely affected one is the respiratory system. Because of the ion imbalance, thick sticky mucus is produced on the surface of the airways which then prevents the removal of dust particles and bacteria. The main complications of cystic fibrosis are the bacterial infections of the respiratory system which become chronic during the patient's life and thus are the most common causes of the respiratory failure and premature death. The most important agents causing these infections are Pseudomonas aeruginosa and Burkholderia cepacia (Bcc). Infections caused by those bacteria are practically untreatable and serious complications arise from the existence of epidemic strains which can be transfered from patient to patient. Precise and fast diagnostics of pathogenic strains is a critical step to avoid spreading bacterial infections as well as strictly followed anti- epidemic strategies mainly based on isolation of cystic fibrosis patients according to...
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Application potential of modification approaches (chemical agents, photo-nanoprobes) and mass spectrometry to study protein structure and protein-protein interaction
Ptáčková, Renata ; Šulc, Miroslav (advisor) ; Levová, Kateřina (referee) ; Osička, Radim (referee)
A comprehensive understanding of physiological role of proteins requires knowledge of their three-dimensional structure, dynamics and protein-protein interactions. Chemical cross-linking in combination with mass spectrometry represents an alternative approach to standard methods for protein structure elucidation (X-ray crystalography, NMR spectroscopy) and enables characterization of interaction interface within protein complexes in their native states. The presented thesis is mainly focused on novel cross-linking methodology based on the in vivo incorporation of methionine analog with photo-reactive functional group (photo-Met) into the sequence of studied protein (so called protein photo-nanoprobe). Interaction between two molecules of 14-3-3zeta protein was used as a model to test and optimize the protein photo-nanoprobe production. The findings confirmed usefulness of this approach for mapping the protein-protein interactions. The photo-initiated cross-linking was used to detect the heterooligomeric membrane structures of cytochromes P450 2B4 and b5 and the molar ratio of cytochromes within individual complexes was assessed. The chemical cross-linking in combination with mass spectrometry was employed to characterize the interaction of their catalytic domains and two mutual orientations of...
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