Regulation der Aktivität und Lokalisation von Antiterminatorproteinen der BglG-Familie
Regulation of the Activity and Localization of BglG family Antiterminator Proteins
by Fabian Rothe
Date of Examination:2012-03-23
Date of issue:2012-11-12
Advisor:Prof. Dr. Jörg Stülke
Referee:Prof. Dr. Jörg Stülke
Referee:Prof. Dr. Kai Tittmann
Referee:PD Dr. Stephan Seiler
Persistent Address:
http://dx.doi.org/10.53846/goediss-1457
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Abstract
English
The regulation of gene expression is essential for all bacteria and allows adapting to changing life conditions. Different transcription and translation factors have an important impact on gene regulation. The antermination proteins of the BglG/ SacY family are widely spread. They control the expression of genes and operons which are involved in the uptake and utilization of different carbon sources. The substrate and phosphorylation dependent activation of the BglG/ SacY family proteins enable these antiterminators to bind their target RNA and allow proceeding the blocked transcription. The transcription factor BglG of Escherichia coli is equivalent to LicT of Bacillus subtilis. Nobody has yet found out whether these two antitermination proteinsare identical and if they have the same function in both organisms. In contrast to LicT, the activation mechanism of BglG is not fully answered yet. Compared to BglG the localization of active and inactive LicT is also unclear. In this work it was shown that BglG is phosphorylated and activated by HPr or FruB which is a homolog to HPr. Furthermore, the phosphorylation dependent dynamic localization of LicT was detected. In vitro experiments could show that BglG is phosphorylated by HPr (or FruB) and thereby activated at histidine-208. Moreover, fluorescence microscopy detected, that inactive LicT (in the absence of beta-glucosides) is constantly distributed in the cytoplasm and accumulates in the cell poles in its active state (after the addition of beta-glucosides). Mutation analysis of the conserved phosphorylation sites of LicT revealed that the state of phosphorylation has an influence on the dynamic localization of LicT regardless of the LicT activity. The results show that the control mechanism of E. coli BglG is identical to B. subtilis LicT and to the other members of BglG / SacY family. Moreover, it was found that the LicT controlled regulation of gene expression is more than a simple mechanism, but rather a highly dynamic process. These observations suggest that there must be more dynamic localization processes among the many regulatory mechanisms. Further studies may elucidate those factors which influence post-translational modifications and the dynamic protein localization.
Keywords: LicT; BglG; phosphorylation; antiterminator; RNA regulation; Escherichia coli; Bacillus subtilis; dynamic protein localisation; phosphotransferase system; gene regulation; FruB; HPr
Other Languages
Die Regulation der Genexpression ist
essentiell für alle Bakterien und ermöglicht die Anpassung an sich
verändernde Lebensbedingungen. Verschiedene Transkriptions- und
Translationsfaktoren haben bei dieser Regulation eine große
Bedeutung. Die Antiterminationsproteine der BglG/ SacY-Familie sind
in Bakterien weit verbreitet und steuern die Expression von Genen
und Operons, die an der Aufnahme und Verwertung von
Kohlenstoffquellen beteiligt sind. Die substrat- und
phosphorylierungsabhängige Aktivierung der Proteine der BglG/
SacY-Familie erlaubt es ihnen, an ihre Ziel-RNA zu binden und
ermöglicht das Fortschreiten der blockierten Transkription. Der
Transkriptionsfaktor BglG aus Escherichia coli ist
Schlagwörter: LicT; BglG; Phosphorylierung; Antitermination; RNA-Regulation; Escherichia coli; Bacillus subtilis; dynamische Proteinlokalisation; Phosphotransferasesystem; Genregulation; FruB; HPr