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dc.contributor.advisor Stülke, Jörg Prof. Dr.
dc.contributor.author Weiß, Martin
dc.date.accessioned 2019-07-26T08:31:01Z
dc.date.available 2019-07-26T08:31:01Z
dc.date.issued 2019-07-26
dc.identifier.uri http://hdl.handle.net/21.11130/00-1735-0000-0003-C177-D
dc.language.iso eng de
dc.relation.uri http://creativecommons.org/licenses/by-nc-nd/4.0/
dc.subject.ddc 570 de
dc.title A protein in search of a function: The c-di-AMP-binding protein DarA of Bacillus subtilis de
dc.type doctoralThesis de
dc.contributor.referee Stülke, Jörg Prof. Dr.
dc.date.examination 2019-01-17
dc.description.abstracteng Adaptation to changing environmental conditions is crucial for any organism to thrive in nature. Bacteria like the Gram-positive model organism Bacillus subtilis have evolved so-called second messengers to facilitate signal transduction processes. An important and unique second messenger is cyclic di-AMP (c-di-AMP) which has been discovered ten years ago. This small molecule has attracted much attention as it is essential for many bacteria that produce it but also can become toxic upon accumulation. Accordingly, it has been coined “essential poison”. In B. subtilis an essential function of c-di-AMP is the regulation of potassium homeostasis and the second messenger is nonessential when the cation is scarce. More advances in the last years refined the essential role of c-di-AMP as it becomes dispensable in several different bacteria under very specific growth conditions or by accumulation of suppressor mutations. It seems that the superordinate function of the small molecule is the adjustment of the cellular turgor by interaction with a plethora of targets. One major target is the PII-like protein DarA. PII proteins form one of the largest families of signal transduction proteins and are nearly ubiquitous in bacteria. These proteins bind low-molecular weight effectors and interact with a variety of targets to control nitrogen metabolism. DarA structurally resembles these classical PII proteins but binds c-di-AMP instead of ATP, ADP or 2-oxoglutarate. DarA is conserved in almost all c-di-AMP-producing firmicutes. Despite extensive efforts prior to this work the function of DarA has remained enigmatic. In this work, we conducted a large unbiased phenotype screening, but this did not reveal the function of DarA to us. However, we could show that DarA is interacting with a cytosolic target. Furthermore, we provide and discuss evidence that DarA is involved in glutamate metabolism and that apo-DarA is toxic for a c-di-AMP-free strain on rich medium. Apo-DarA most likely promotes a metabolic flux towards glutamate and arginine synthesis which is revealed in B. subtilis cells experiencing extreme potassium limitation. These cells accumulate positively charged amino acids derived from glutamate like ornithine, citrulline or arginine to compensate the lack of sufficient intracellular K+ amounts. Surprisingly, DarA is needed for this compensatory mechanism. Our results show that DarA has to act on a target that feeds into the arginine biosynthesis. Structurally and rationally the glutamate synthase GltAB is the most promising interaction partner of DarA. Although unambiguous evidence for an interaction with GltAB is still pending, the established connection of DarA to glutamate metabolism will be crucial for further investigation. The results are especially interesting since the homeostases of c-di-AMP, K+ and glutamate are somehow intricately intertwined but no target of c-di-AMP has been reported to be involved in the homeostasis of glutamate until this thesis. In addition, we show that c-di-AMP is not only dispensable at low K+ concentrations, as reported before, but also when the cation is highly abundant. This contributes to a model of cellular turgor regulation by c-di-AMP. Although the interaction partner of DarA has escaped detection, we have linked DarA to glutamate metabolism which might aid the elucidation of c-di-AMP and glutamate homeostasis interconnections in the future. de
dc.contributor.coReferee Commichau, Fabian Prof. Dr.
dc.contributor.thirdReferee Ficner, Ralf Prof. Dr.
dc.contributor.thirdReferee Klumpp, Stefan Prof. Dr.
dc.contributor.thirdReferee Daniel, Rolf Prof. Dr.
dc.contributor.thirdReferee Lüder, Carsten Prof. Dr.
dc.subject.eng Bacillus subtilis de
dc.subject.eng c-di-AMP de
dc.subject.eng DarA de
dc.subject.eng c-di-AMP-binding protein de
dc.subject.eng protein-protein interaction de
dc.subject.eng signal transduction de
dc.subject.eng PII-like de
dc.identifier.urn urn:nbn:de:gbv:7-21.11130/00-1735-0000-0003-C177-D-4
dc.affiliation.institute Göttinger Graduiertenschule für Neurowissenschaften, Biophysik und molekulare Biowissenschaften (GGNB) de
dc.subject.gokfull Biologie (PPN619462639) de
dc.identifier.ppn 1672306906

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