Berlin 2012 – scientific programme

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BP: Fachverband Biologische Physik

BP 9: Focus: Systems Biology of Bacteria (with jDPG)

BP 9.5: Talk

Tuesday, March 27, 2012, 11:30–11:45, E 020

A Plausible Mechanism for the Generation of Ultrasensitivity and Bistability in Bacterial Two-Component Systems — •Ronny Straube — Max Planck Institute for Dynamics of Complex Technical Systems, Magdeburg

Two-component systems are the simplest signal processing units mostly found in bacteria. They consist of a histidine kinase (HK) and a cognate response regulator (RR) which often acts as a transcription factor. Upon stimulation the HK undergoes autophosphorylation and, subsequently, transfers the phosphate group to the RR. In addition, many HKs also exhibit phosphatase activity towards the phosphorylated form of the RR. The relative activity between autophosphorylation, kinase and phosphatase mode is often regulated by small allosteric effectors. Using a simple mathematical model I show that if the kinase and phosphatase activities are regulated in a reciprocal fashion two-component systems can generate highly sigmoidal responses (ultrasensitivity) quite similar to covalent modification systems in eukaryotes [1]. Under proper kinetic conditions the response can even become hysteretic with an intermediate bistable regime. Hence, despite the bifunctional nature of the HK switch-like all-or-none responses could already be generated at the protein-protein level without genetic regulation. [1] Goldbeter A, Koshland, DE Jr. An amplified sensitivity arising from covalent modification in biological systems. Proc. Natl. Acad. Sci USA 78, 6840-6844 (1981).