| 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.identifier.uri | http://dx.doi.org/10.53846/goediss-7577 | |
| dc.language.iso | eng | de |
| dc.rights.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 | |