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Sci. STKE, 6 November 2007
Vol. 2007, Issue 411, p. tw407
[DOI: 10.1126/stke.4112007tw407]

EDITORS' CHOICE

Systems Biology Dissecting a Core Oscillator

Beverly A. Purnell

Science, AAAS, Washington, DC 20005, USA

The core circadian oscillator of the cyanobacterium Synechococcus elongatus can be reconstituted in vitro by mixing the proteins KaiA, KaiB, and KaiC, resulting in oscillations in KaiC phosphorylation. The underlying mechanism of this biochemical oscillator has been elusive. Rust et al. (see the Perspective by Poon and Ferrell) now show that phosphorylation of KaiC at two residues is cyclically ordered and that the abundance of each phosphorylated form determines the phase of the oscillator. This sequential phosphorylation of KaiC, combined with negative feedback caused by one of the phosphorylation states, is sufficient to explain stable oscillation.

M. J. Rust, J. S. Markson, W. S. Lane, D. S. Fisher, E. K. O'Shea, Ordered phosphorylation governs oscillation of a three-protein circadian clock. Science 318, 809-812 (2007). [Abstract] [Full Text]

A. C. Poon, J. E. Ferrell Jr., A clock with a flip switch. Science 318, 757-758 (2007). [Summary] [Full Text]

Citation: B. A. Purnell, Dissecting a Core Oscillator. Sci. STKE 2007, tw407 (2007).

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