Dokument: Kontrolle der Eisen-Homöostase in Corynebacterium glutamicum durch ein hierarchisches regulatorisches Netzwerk
| Titel: | Kontrolle der Eisen-Homöostase in Corynebacterium glutamicum durch ein hierarchisches regulatorisches Netzwerk | |||||||
| Weiterer Titel: | Control of iron homeostasis in Corynebacterium glutamicum by a hierarchical regulatory network | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=6539 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20071214-103413-7 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Prof. Dr. Frunzke, Julia [Autor] | |||||||
| Dateien: |
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| Beitragende: | Prof. Dr. Bott, Michael [Gutachter] Prof. Dr. Wagner, Rolf [Gutachter] | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 570 Biowissenschaften; Biologie | |||||||
| Beschreibung: | Iron is an essential trace element for nearly all organisms as it participates in major biological processes, but on the other hand it poses problems of poor solubility and toxicity. Therefore, many organisms have evolved sophisticated mechanisms to ensure sufficient but not excess levels of intracellular iron. In Corynebacterium diphtheriae the transcriptional regulator DtxR in complex with Fe2+ represses transcription of genes involved in iron acquisition under iron excess. In this work the control of iron homeostasis on the transcriptional level was investigated in the Gram-positive soil bacterium Corynebacterium glutamicum, a non-pathogenic relative of C. diphtheriae.
In C. glutamicum DtxR directly regulates transcription of about 60 genes involved in iron uptake, iron storage and synthesis of iron sulfur clusters in response to iron availability. The majority of these genes are repressed by DtxR and encode high affinity iron uptake systems, such as siderophore ABC transporters, siderophore binding proteins as well as heme transport systems and heme oxygenase. On the other hand, DtxR seems to act as a direct activator of the iron storage proteins ferritin and Dps under conditions of sufficient iron supply. These results clearly emphasize DtxR as the master regulator of iron-dependent gene expression in C. glutamicum. In studies with a dtxR deletion mutant an increased induction rate of the CGP3 prophage was observed. Subsequently, it was shown that this prophage is induced spontaneously not only in this mutant but also in a small fraction of C. glutamicum wild type cells (<5%). Evidence for lysis of cells containing several CGP3 phage DNA molecules was obtained. Three of the genes repressed by DtxR, ripA, cgtR11 and cg0527, encode themselves transcriptional regulators. Under iron limitation the AraC-type regulator RipA acts as a repressor of genes encoding several prominent iron-containing proteins, such as aconitase, succinate dehydrogenase, catalase or nitrate reductase. By the reduced synthesis of these proteins, the cell is probably able to sustain more important iron-requiring processes, like respiration or DNA biosynthesis. CgtR11, the response regulator of the two-component system CgtSR11, directly activates expression of the hmuO gene encoding heme oxygenase in a heme-dependent manner. This enzyme is required for the utilization of heme as an iron source by C. glutamicum, which occurs under iron deprivation. Moreover, strong evidence could be provided that the CgtSR11 two-component system is also involved in the regulation of heme biosynthesis as well as in the production of heme-containing proteins in response to iron and heme availability. The Cg0527 protein is a member of the ArsR family of transcriptional regulators, which are often involved in the adaptation to high concentrations of heavy metal ions, but its exact function is still unknown. Altogether, the four transcriptional regulators DtxR, RipA, CgtR11 and Cg0527 constitute a hierarchical regulatory network controlling iron homeostasis in Corynebacterium glutamicum. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Sonstige Einrichtungen/Externe | |||||||
| Dokument erstellt am: | 13.12.2007 | |||||||
| Dateien geändert am: | 13.12.2007 | |||||||
| Promotionsantrag am: | 26.10.0007 | |||||||
| Datum der Promotion: | 29.11.0007 |
