Berlin 2008 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 20: Regulation and Signaling
BP 20.3: Vortrag
Donnerstag, 28. Februar 2008, 10:30–10:45, C 243
Links between biochemistry and regulatory network design in a bacterial stress response system — •Georg Fritz1, Christiane Koller2, Korinna Burdack2, Ulrich Gerland1, and Kirsten Jung2 — 1Institute for Theoretical Physics, Universität zu Köln — 2Department of Microbiology, LMU München
The evolutionary driving forces and constraints that have shaped the design of biomolecular networks are poorly understood in general. Here, we focus on a conditional stress response system, the Cad system of E. coli, which is triggered under acidic stress only if lysine is abundant externally. Through lysine import, decarboxylation, and cadaverine export, it effectively expels H+ from the cytoplasm. A salient feature of the Cad system is that its expression is transient, even when the low-pH and high-lysine conditions for its induction persist. The transient behavior is believed to be caused by a negative feedback via external cadaverine.
We have experimentally recorded the dynamics of the Cad system with a high time resolution, and formulated a quantitative model for its function and regulation. Our analysis suggests that the system design is linked to the biochemical properties of a key system component, the antiporter CadB: Limited specificity of the antiporter causes a futile transport cycle at high external cadaverine levels. Interestingly, the external cadaverine threshold for the negative feedback appears quantitatively consistent with the specificity of the antiporter, suggesting that the regulatory feedback and the biochemistry of the antiporter are evolutionarily linked.