6 results on '"Michaela Fritz"'
Search Results
2. The Binary Clostridium botulinum C2 Toxin as a Protein Delivery System
- Author
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Michaela Fritz, Robert Roebling, Holger Barth, and Klaus Aktories
- Subjects
Toxin ,Clostridium limosum ,Cell Biology ,Biology ,medicine.disease_cause ,Biochemistry ,Fusion protein ,Cytosol ,Fusion Toxin ,Cytoplasm ,medicine ,Clostridium botulinum ,Molecular Biology ,Actin - Abstract
The binary Clostridium botulinum C2 toxin is composed of the enzyme component C2I and the binding component C2II, which are individual and non-linked proteins. Activated C2IIa mediates cell binding and translocation of C2I into the cytoplasm. C2I ADP-ribosylates G-actin at Arg-177 to depolymerize actin filaments. A fusion toxin containing the N-terminal domain of C2I (residues 1–225) transports C3 ADP-ribosyltransferase from Clostridium limosum into cells (Barth, H., Hofmann, F., Olenik, C., Just, I., and Aktories, K. (1998) Infect. Immun. 66, 1364–1369). We characterized the adaptor function of C2I and its interaction with C2IIa. The fusion toxin GST-C2I1–225-C3 was efficiently transported by C2IIa, indicating that C2IIa translocates proteins into the cytosol even when the C2I1–225 adaptor was positioned in the middle of a fusion protein. Amino acid residues 1–87 of C2I were sufficient for interaction with C2IIa and for translocation of C2I fusion toxins into HeLa cells. Residues 1–87 were the minimal part of C2I to bind to C2IIa on the cell surface, as detected by fluorescence-activated cytometry. An excess of C2I1–87(but not of further truncated C2I fragments) competed with Alexa488-labeled C2I for binding to C2IIa. Also, the fragment C2I30–431 and the fusion toxin C2I30–225-C3 competed with C2I-Alexa488 for binding to C2IIa. C2I30–225-C3 did not induce cytotoxic effects on cells when applied together with C2IIa, indicating that amino acid residues 1–29 are involved in translocation of C2I but are not absolutely essential for binding to C2IIa.
- Published
- 2002
3. More than urns: A multi-method pipeline for analyzing cremation burials
- Author
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Lukas Waltenberger, Marjolein D. Bosch, Michaela Fritzl, André Gahleitner, Christoph Kurzmann, Maximilian Piniel, Roderick B. Salisbury, Ladislav Strnad, Hannah Skerjanz, Domnika Verdianu, Christophe Snoeck, Fabian Kanz, and Katharina Rebay-Salisbury
- Subjects
Medicine ,Science - Abstract
Burial rites of archaeological populations are frequently interpreted based on cremated remains of the human body and the urn they were deposited in. In comparison to inhumations, information about the deceased is much more limited and dependent on fragmentation, selection of body regions, taphonomic processes, and excavation techniques. So far, little attention has been paid to the context in which urns are buried. In this study, we combined archaeological techniques with anthropology, computed tomography, archaeobotany, zooarchaeology, geochemistry and isotopic approaches and conducted a detailed analysis on a case study of two Late Bronze Age urns from St. Pölten, Austria (c. 1430 and 1260 cal. BCE). The urns were recovered en-bloc and CT-scanned before the micro-excavation. Osteological and strontium isotope analysis revealed that the cremated remains comprised a young adult female and a child that died at the age of 10–12 years. Both individuals had been subject to physiological stress and were likely local. Animal bones burnt at different temperatures suggested different depositional pathways into the urn and pit as part of the pyre, food offerings, and unintentional settlement debris. Eight wild plant and five crop plant species appeared as part of the local landscape, as food offerings and fire accelerants. Sediment chemistry suggests that pyre remains were deposited around the urns during burial. Multi-element geochemistry, archaeobotany, and zooarchaeology provide insights into the Late Bronze Age environment, the process of cremation, the gathering of bones and final funerary deposition.
- Published
- 2023
4. Characterization of the Enzymatic Component of the ADP-Ribosyltransferase Toxin CDTa from Clostridium difficile
- Author
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Klaus Aktories, Irene Gülke, Gunther Pfeifer, Holger Barth, Michaela Fritz, Jan Liese, and Fred Hofmann
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Clostridium perfringens ,Bacterial Toxins ,Immunology ,medicine.disease_cause ,Microbiology ,Substrate Specificity ,Bacterial Proteins ,Chlorocebus aethiops ,medicine ,Animals ,Cloning, Molecular ,Vero Cells ,Escherichia coli ,ADP Ribose Transferases ,Alanine ,chemistry.chemical_classification ,biology ,Clostridioides difficile ,Toxin ,Molecular Pathogenesis ,Molecular biology ,Enzyme assay ,Infectious Diseases ,Enzyme ,Biochemistry ,chemistry ,Mutagenesis ,ADP-ribosylation ,biology.protein ,Clostridium botulinum ,Parasitology ,Poly(ADP-ribose) Polymerases - Abstract
Certain strains of Clostridium difficile produce the ADP-ribosyltransferase CDT, which is a binary actin ADP-ribosylating toxin. The toxin consists of the binding component CDTb, which mediates receptor binding and cellular uptake, and the enzyme component CDTa. Here we studied the enzyme component (CDTa) of the toxin using the binding component of Clostridium perfringens iota toxin (Ib), which is interchangeable with CDTb as a transport component. Ib was used because CDTb was not expressed as a recombinant protein in Escherichia coli . Similar to iota toxin, CDTa ADP-ribosylates nonmuscle and skeletal muscle actin. The N-terminal part of CDTa (CDTa 1–240 ) competes with full-length CDTa for binding to the iota toxin binding component. The C-terminal part (CDTa 244–263 ) harbors the enzyme activity but was much less active than the full-length CDTa. Changes of Glu428 and Glu430 to glutamine, Ser388 to alanine, and Arg345 to lysine blocked ADP-ribosyltransferase activity. Comparison of CDTa with C. perfringens iota toxin and Clostridium botulinum C2 toxin revealed full enzyme activity of the fragment Ia 208–413 but loss of activity of several N-terminally deleted C2I proteins including C2I 103–431 , C2I 190–431 , and C2I 30–431 . The data indicate that CDTa belongs to the iota toxin subfamily of binary actin ADP-ribosylating toxins with respect to interaction with the binding component and substrate specificity. It shares typical conserved amino acid residues with iota toxin and C2 toxin that are suggested to be involved in NAD-binding and/or catalytic activity. The enzyme components of CDT, iota toxin, and C2 toxin differ with respect to the minimal structural requirement for full enzyme activity.
- Published
- 2001
5. Dominance of the BV17 element in nickel-specific human T cell receptors relates to severity of contact sensitivity
- Author
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Michaela Fritz, Hans Ulrich Weltzien, Anne Dormoy, Corinne Moulon, and Jörg Vollmer
- Subjects
Receptors, Antigen, T-Cell, alpha-beta ,T-Lymphocytes ,Molecular Sequence Data ,Immunology ,Peptide ,Complementarity determining region ,Biology ,Lymphocyte Activation ,Major histocompatibility complex ,Polymerase Chain Reaction ,Cell Line ,HLA Antigens ,Nickel ,medicine ,Humans ,Immunology and Allergy ,Amino Acid Sequence ,DNA Primers ,Dominance (genetics) ,Genetics ,chemistry.chemical_classification ,Base Sequence ,T-cell receptor ,Reproducibility of Results ,DNA ,T lymphocyte ,Human serum albumin ,Molecular biology ,Clone Cells ,Amino acid ,chemistry ,Dermatitis, Allergic Contact ,biology.protein ,medicine.drug - Abstract
Hypersensitivity to nickel (Ni) represents the most common manifestation of contact allergy in humans. The role of metal-specific T cells in this disease is well established, but the molecular interactions involved in their activation are poorly understood. We examined the T cell receptor (TCR) repertoire in T cells activated with either NiSO4 or NiSO4-treated human serum albumin from six allergic patients. For the three most hyperreactive donors, we found a strong over-representation of the TCR BV17 element. TCR sequencing for one of these donors revealed an additional skewing for AV1 as well as a selection for an N region encoded argine at position 95 of the BV17 complementarity determining region (CDR)3. Since Arg is not known to participate in Ni complexing, we suppose that this selection is driven by contacts with peptide rather than nickel. However, the CDR1 of BV17 contains a unique combination of amino acids (HDA) that bears similarities to known motifs in Ni-binding proteins or peptides. We therefore propose that the severe hypersensitivity reactions found in BV17 over-expressors may be the result of Ni2+ ions bridging the germ-line-encoded BV17 CDR1 loop to corresponding sites in the major histocompatibility complex/peptide complex and thereby creating a superantigen-like enhancement of weak TCR-peptide contacts.
- Published
- 1997
6. Temporal expression of adhesion factors and activity of global regulators during establishment of Staphylococcus aureus nasal colonization
- Author
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Andreas Peschel, Marc Burian, Clemens Unger, Wolfgang Hoffmann, Michaela Fritz, Maren Rautenberg, Bernhard Krismer, Christiane Goerke, Christiane Wolz, and Thomas P. Kohler
- Subjects
Staphylococcus aureus ,Virulence ,Biology ,medicine.disease_cause ,Microbiology ,Bacterial Proteins ,Gene expression ,medicine ,Immunology and Allergy ,Animals ,Humans ,Colonization ,Cotton rat ,Sigmodontinae ,Adhesins, Bacterial ,Gene ,Regulation of gene expression ,Antigens, Bacterial ,Reverse Transcriptase Polymerase Chain Reaction ,Gene Expression Regulation, Bacterial ,Staphylococcal Infections ,biology.organism_classification ,Bacterial adhesin ,Disease Models, Animal ,Nasal Mucosa ,RNA, Bacterial ,Infectious Diseases ,Genes, Bacterial ,Trans-Activators - Abstract
The human pathogen Staphylococcus aureus successfully colonizes its primary reservoir, the nasal cavity, most likely by regulatory adaptation to the nose environment. Cotton rats represent an excellent model for the study of bacterial gene expression in the initial phases of colonization. To gain insight into the expression profile necessary for the establishment of colonization, we performed direct transcript analysis by quantitative real-time reverse-transcription polymerase chain reaction on cotton rat noses removed from euthanized animals on days 1, 4, or 10 after instillation of 2 human S. aureus nose isolates. Global virulence regulators (agr, sae) were not active in this early phase, but the essential 2-component regulatory system WalKR seems to play an important role. Accordingly, an elevated expression of walKR target genes (sak, sceD) could be detected. In agreement with previous studies that demonstrated the essential role played by wall teichoic acid (WTA) polymers in nasal colonization, we detected a strongly increased expression of WTA-biosynthetic genes. The expression profile switched to production of the adhesive proteins ClfB and IsdA at later stages of the colonization process. These data underscore the temporal differences in the roles of WTA and surface proteins in nasal colonization, and they provide the first evidence for a regulation of WTA biosynthesis in vivo.
- Published
- 2010
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