|
|
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...
|
|
|
Isolation of Quorum Sensing Inhibitory compounds from cyanobacteria
MACHO, Markéta
Overuse of antibiotics has led to the development of resistance in many medically relevant human pathogens, posing a threat to human health. The recent decline in the discovery of novel antibiotics together with development of multi-antibiotic resistant strains demands a search of an alternative approach. Anti-virulence therapy poses significantly lower pressure on developing resistance given its focus on disarming the pathogen rather than eradicating it. Advancement in the field of bacterial cell-to-cell communication (Quorum Sensing, QS) and its molecular mechanism regulating the production of virulence factors in many clinically relevant human pathogens led to the discovery of Quorum Sensing inhibitory (QSI) molecules. Cyanobacteria are recognized as a prolific source of natural bioactive compounds with great pharmacological potential. The aim of this study was to screen cyanobacterial extracts for QSI activity in search of potential anti-virulence drugs. 45 cyanobacterial strains were randomly selected from the in-house culture collection of Centre Algatech, extracted, and fractionated to generate 1575 fractions for QSI evaluation. Strains 3, 16, and 113 exhibited the highest inhibitory potential against both used biosensors, E. coli pSB401 and E. coli pSB1075. The obtained results open a future prospect to isolate and elucidate the lead molecule responsible for QSI activity.
|
|
|
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)...
|
|
|
Melectin analogues: The influence of dendrimerization on antimicrobial and hemolytic activity
Niederhafner, Petr ; Šafařík, Martin ; Ježek, Jan ; Borovičková, Lenka ; Bednárová, Lucie ; Fučík, Vladimír ; Čeřovský, Václav ; Slaninová, Jiřina
Dimers and tetramers of MEP and MEP derivatives were synthesized on Fmoc-Lys(Fmoc)-Rink amide resin, the tetramer was obtained from the dimer C-terminally extended via Cys-Cys linkage. In general, the dendrimerization of MEP led to an increase of haemolytic activity but did not improve substantially its antimicrobial properties.
|
guest ::
