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BP: Fachverband Biologische Physik

BP 2: Protein Structure \& Dynamics

BP 2.3: Vortrag

Montag, 14. März 2011, 11:00–11:15, ZEU 260

Concurrent Enzymatic Reactions as a Source of Bistability in Single Protein Modification Cycles — •Ronny Straube — MPI for Dynamics of Complex Technical Systems, Magdeburg, Germany

It is well known that reversible protein modifications can generate ultrasensitivity when the modifying enzymes operate in saturation [1]. They can also exhibit bistability if the substrate protein is antagonistically modified at multiple sites [2]. However, in the mathematical description of such mechanisms it is often neglected that the activity and/or substrate affinity of the modifying enzymes (e.g. kinase and phosphatase) is often itself regulated through reversible binding of allosteric effectors which can inter convert the respective enzyme species between a high and a low catalytic activity form. Here, I show that the concurrent action of such different activity forms of an antagonistic enzyme pair can generate a bistable system response already at the level of a single protein modification cycle, i.e. without the requirement for multisite modifications. In contrast to other mechanisms [1,2] bistability is predicted to occur even when substrate molecules and enzymes are present in equal amounts. I further show that the same mechanism is also applicable to two component systems which are the most simple signal transduction systems in bacteria. Since the formation of enzyme sub populations is difficult to avoid both in vivo and in vitro concurrent enzymatic reactions might be a ubiquitous source for generating bistability in biological systems. [1] A. Goldbeter and D. E. Koshland Jr. PNAS 78, 6840 (1981). [2] N. I. Markevich, J. B. Hoek and B. N. Kholodenko J. Cell Biol. 164 353 (2004).