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Common features of the biosynthetic pathways of lincomycin,some pyrrolo-1,4-benzodiazepines and hormaomycin
Steiningerová, Lucie ; Janata, Jiří (advisor) ; Mašek, Tomáš (referee)
Lincosamides, pyrrolo-1,4-benzodiazepines (PBD) and hormaomycin are biologically active substances differing in their structure and mode of action. Lincosamides lincomycin and clindamycin are clinically used antibiotics, PBD exhibit antitumor activity and hormaomycin is a bacterial hormone. Unusual precursor, 4-propyl-L-proline (PPL) derived from L-tyrosine is incorporated in the lincomycin structure. Surprisingly, structurally and functionally dissimilar hormaomycin and some PBD (tomaymycin, anthramycin, sibiromycin) incorporate L-proline derivative with two- or three- carbon side chain of the same biosynthetic origin. Accordingly, a set of orthologous genes coding for biosynthesis of these structurally similar precursors has been found in appropriate biosynthetic gene clusters. There is a clear evolutionary relationship among the biosynthesis of lincomycin, hormaomycin and some PBD. However, the evolutionary origin of PPL pathway is not known as well as its further development. Only a limited number of naturally occured modifications of the pathway has been described and the history of supposed horizontal gene transfers of biosynthetic genes remains unknown. Answers to these questions are particularly important due to the preparation of new hybrid substances with improved bioactive effects using methods...
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Molecular analysis of resistance gene vga(A)LC identification of key aminoacid residues.
Kroová, Michaela ; Najmanová, Lucie (advisor) ; Vopálenský, Václav (referee)
Protein Vga(A) gives staphylococci resistance to streptogramins A. The recently discovered protein Vga(A)LC differs from Vga(A) only by 7 amino acid residues, but this difference is sufficient for shift of its substrate specificity towards lincosamides. The group of four amino acids in the central part of protein (LGAG in Vga(A) and SVTS in Vga(A)LC) was detected to be crucial for the substrate specificity. In this diploma thesis 5 alternativesets of vga(A)LC gene point mutations were prepared in order to determine the impact of individual amino acids of the aforementioned group on the resistance phenotype. Mutations were prepared in vector pGEM® -T and cloned into shuttle vector pRB374. The prepared constructs were transformed by electroporation into the sensitive strain of Staphylococcus aureus RN4220 and values of minimum inhibitory concentration (MIC) were measured for lincomycin, clindamycin and pristinamycin IIA by the agar dilution method. The transformation was not successful in one of the mutations. Results of setting MIC for the remaining four mutations do not make it possible to specify uniquely the ratio of individual amino acids for determining substrate specificity. Two of the amino acids were found to be important. We anticipate preparation of more mutations.
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Preparation and characterization of LmbX protein involved in lincomycin biosynthesis
Jiráčková, Petra ; Janata, Jiří (advisor) ; Janderová, Blanka (referee)
Lincomycin is an antibiotic used in clinical praxis. It is produced by Streptomyces lincolnensis. Lincomycin is composed of an amino-sugar and an amino-acid moiety linked by an amide bond. The amino-acid precursor is propylproline (PPL), whose biosynthesis undergoes the pathway derived from tyrosine. The modified PPL biosynthesis pathway was also discovered in pyrrolobenzodiazepines (PBD) and hormaomycin. In the biosynthesis of PBD the PPL precursor is further modified by reactions catalysed by specific enzymes missing in the biosynthesis of lincomycin. The genes encoding these enzymes could be transferred to the lincomycin biosynthetic gene cluster. In this way we could get producers of hybrid antibiotics with better properties and even antimalaric effects. Six enzymes participate in PPL biosynthesis, which are encoded in the lincomycin biosynthetic gene cluster. The first two reactions of PPL biosynthesis pathway are proven, therefore, this work focuses on the third reaction that is supposed to be catalysed by protein LmbX according to literature. The proposed function of LmbX is a hydrolysis of C-C bond. However, LmbX belongs to the protein family of isomerases by sequence homology. The protein LmbX was overproduced in this work and its activity was tested in the presence of the expected...
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The effect of aminoacid variability on the resistance phenotype in ARE subfamily of ABC proteins
Lenart, Jakub ; Balíková Novotná, Gabriela (advisor) ; Fišer, Radovan (referee)
ARE subfamily proteins belonging to ABC transporters confers a different degree of resistance to macrolides, linkosamides and streptogramins antibiotics. Among the most clinically ARE subfamily proteins in staphylococci is Vga(A) protein lead to the award resistance to streptogtramins A. In 2006, discovered the new variant called the Vga(A)LC, which in addition to streptogramins A resistance also confers linkosamides. Vga(A) and Vga(A)LC differ in only 7 amino acids, yet confer different resistance phenotypes. In previous experiments it was found that the central role in determining substrate specificity play a 4 amino acid differences that accumulate in the section of 15 amino acids within the linker connecting the two ABC domains (positions 212, 219, 220 and 226). The combination of amino acids LGAG Vga(A) increases resistance to streptogramins A while present in combination SVTS Vga(A)LC increased resistance to linkosamides. Although in this subfamily includes a large number of resistance proteins, the mechanism of resistance has not yet been established with certainty. The aim was to create a new Vga(A) variants that contain specific combinations of amino acids for Vga(A) and Vga(A)LC protein at positions 212, 219, 220 and 226 and compared their ability to grant resistance to linkosamides. We also...
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Antibiotic resistance conferred by members of ARE subfamily of ABC proteins
Veselá, Ludmila ; Balíková Novotná, Gabriela (advisor) ; Borčin, Kateřina (referee)
The main topic of this thesis is the ARE subfamily of ABC transporters. The importance of the proteins of this subfamily lies in the fact that they confer resistance to several classes of clinically important antibiotics: macrolides, lincosamides, streptogramines and pleuromutilines and they do it in significant pathogens, as for example Staphylococcus aureus. Compared to canonical ABC transporters, the structure of ABC proteins lacks the transmembrane domain (TMD) and so far, there where not even found an integrating transmembrane protein. Due to these facts, the mechanism of resistance conferred by these proteins remains unclear. In the thesis, both suggested hypotheses of the mechanism of how these proteins work are discussed. The first hypothesis presumes the active efflux of antibiotics out of the bacteria. The second hypothesis suggests release of antibiotic from its binding site initiated by ARE proteins, followed by its passive diffusion out of the cell. Keywords: ABC proteins, ARE proteins, resistance, MLS, Vga
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Mechanismus rezistence makrolidů a linkosamidů v koaguláze negativních stafylokoků v ČR a nové typy na linkosamid resistentních S. haemolyticus
Novotná, Gabriela ; Janata, Jiří ; Spížek, Jaroslav
Objectives: The aim of this study was to investigate an incidence of different resistance mechanisms to macrolides and lincosamides in methicillin-resistant coagulase-negative staphylococci in the Czech Republic. Methods: Phenotypes were determined by triple-disc diffusion method. The presence of the genes ermA, ermC (resistance by target site alteration) msrA (efflux resistance) and linA (resistance by antibiotic inactivation) was tested by Southern blot analysis. A bioassay for the detection of lincomycin inactivation mechanism was performed in lincosamide-resistant strains, where none of the resistance genes was detected. In these strains also PFGE analysis was done. Results: In 99 clinical isolates in vitro resistant to one of erythromycin, lincomycin or clindamycin, triple-disc diffusion method reveals seven different phenotypes corresponding with resistance mechanisms. The resistance was mainly due to the presence of msrA gene, which was detected in 53 strains. Genes ermC and ermA were detected in 42 strains and the linA was detected in 28 strains. In 15 lincosamides-resistant strains no resistance gene was detected. Lincosamides were not inactivated in those strains indicating a new type of resistance different from inactivation. Conclusion: The dissemination of resistance types differs strongly from the published data. While in other countries cross-resistance to macrolides and lincosamides conferred by ermA and ermC predominates, in the Czech Republic the gene msrA is the most frequent genetic determinant conferring resistance to macrolides only. It follows that one third of macrolide-resistant staphylococci remains lincosamide-sensitive. A homogenous group of lincosamide-resistant S. haemolyticus with unknown resistance mechanism was newly defined.
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