Characterization of proteins of the Asp23 protein family in Bacillus subtilis

von Dominik Tödter
Dissertation
Datum der mündl. Prüfung:2017-01-24
Erschienen:2017-02-07
Betreuer:Prof. Dr. Jörg Stülke
Gutachter:Prof. Dr. Jörg Stülke
Gutachter:Dr. Fabian Moritz Commichau
Zum Verlinken/Zitieren: http://dx.doi.org/10.53846/goediss-6107

 

 

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The acetyl-CoA carboxylase (ACCase) catalyzes the production of malonyl-CoA, the precursor in fatty acid biosynthesis. In almost all organisms, this is a fundamental process since fatty acids are the main components of membrane lipids and serve as precursor for energy supplying pathways. Especially in organisms like the soil bacterium Bacillus subtilis, that have to deal with different and quickly changing environmental conditions, the control of fatty acid homeostasis is important. Although many examples of ACCase regulation are found in other organisms, nothing is known about the regulation of the acetyl-CoA carboxylase in B. subtilis. The aim of this work was the characterization of the Asp23 protein YqhY. It could be shown that YqhY is able to interact with the AccAD subcomplex or the protease ClpCP. Moreover, cells lacking YqhY acquired suppressor mutations that were often located in the subunits of the acetyl-CoA carboxylase. Further investigations demonstrated that some mutations lead to decreased acetyl-CoA carboxylase activity. Therefore, it was assumed that YqhY regulates the activity of the ACCase by either acting as inhibitor or by promoting the degradation of the subunits. Despite these observations, an inhibitory effect of YqhY on the activity of the ACCase complex could not be proven and unchanged protein amounts of the subunits in the absence of ClpP indicated that they are not subject to proteolysis. However, localization experiments displayed the localization dependency of AccA on YqhY, providing the possibility of YqhY impacting the acetyl-CoA carboxylase activity by delocalization of parts of the complex. It is also conceivable that the absence of YqhY causes the accumulation of malonyl-CoA. This highly active compound could nonspecifically acylate many proteins of different pathways, leading to their inactivity and toxic effects for the cell. Although the precise role of YqhY remains elusive, the results of this work indicate a regulatory function in fatty acid synthesis. They provide possible ways how YqhY could be involved in this pathway and serve as a basis for future investigations.
Keywords: Bacillus subtilis; Acetyl-CoA carboxylase; Asp23 proteins; Fatty acid synthesis
 
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