The molecular clockwork of a protein-based circadian oscillator

Markson, Joseph S.; O’Shea, Erin K.

doi:10.1016/j.febslet.2009.11.021

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Volume 583, Issue 24 , Pages 3938-3947, 17 December 2009

The molecular clockwork of a protein-based circadian oscillator

Edited by Stefan Hohmann

Howard Hughes Medical Institute, Faculty of Arts and Sciences Center for Systems Biology, Department of Molecular and Cellular Biology, Department of Chemistry and Chemical Biology, and Graduate Program in Biophysics, Harvard University, Cambridge, MA 02138, USA

Received 6 October 2009; received in revised form 6 November 2009; accepted 9 November 2009. published online 12 November 2009.

Abstract

The circadian clock of the cyanobacterium Synechococcus elongatus PCC 7942 is governed by a core oscillator consisting of the proteins KaiA, KaiB, and KaiC. Remarkably, circadian oscillations in the phosphorylation state of KaiC can be reconstituted in a test tube by mixing the three Kai proteins and adenosine triphosphate. The in vitro oscillator provides a well-defined system in which experiments can be combined with mathematical analysis to understand the mechanism of a highly robust biological oscillator. In this Review, we summarize the biochemistry of the Kai proteins and examine models that have been proposed to explain how oscillations emerge from the properties of the oscillator’s constituents.

Abbreviations: ADP, adenosine diphosphate, ATP, adenosine triphosphate, P_i, inorganic phosphate, U-KaiC, unphosphorylated KaiC, S-KaiC, KaiC phosphorylated only on serine 431, T-KaiC, KaiC phosphorylated only on threonine 432, ST-KaiC, KaiC phosphorylated on both serine 431 and threonine 432