Dresden 2009 – scientific programme

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BP: Fachverband Biologische Physik

BP 18: Regulation and Signaling

BP 18.3: Talk

Thursday, March 26, 2009, 10:30–10:45, HÜL 186

Perfect robust network design of the KaiABC circadian clock — •Christian Brettschneider and Markus Kollmann — Institut für theoretische Biologie, Humboldt Universität zu Berlin

The simple circadian oscillator found in cyanobacteria can be reconstituted in vitro using three proteins - KaiA, KaiB, KaiC. It has been shown that four forms of KaiC differing in their phosphorylation state appear in an ordered pattern. Importantly, it has been revealed that phase, frequency and amplitude of the oscillations do not change under concerted severalfold over- and underexpression of its components. Consequently, the circadian clock is invariant with respect to concerted fluctuations in total protein concentrations of all Kai proteins. This observation is a strong constraint for modeling the circadian clock.

We will present the first quantitative model that includes the ordered pattern of the four KaiC states as well as the measured invariance of concerted variations. The model is systematically developed from intrinsic KaiC autokinase and autophosphatase rates that are modulated by KaiA and KaiB. A formal description shows that the invariance of concerted variations can be achieved by inactivation. In this case, inactivation of KaiA leads to a negative feedback oscillator, that in turn causes synchronization between different KaiC as well as high amplitudes.