In vitro regulation of circadian phosphorylation rhythm of cyanobacterial clock protein KaiC by KaiA and KaiB

Edited by Jesus Avila

Received 25 September 2009; received in revised form 29 December 2009; accepted 8 January 2010. published online 14 January 2010.

Abstract

Biochemical circadian oscillation of KaiC phosphorylation, by mixing three Kai proteins and ATP, has been proven to be the central oscillator of the cyanobacterial circadian clock. In vivo, the intracellular levels of KaiB and KaiC oscillate in a circadian fashion. By scrutinizing KaiC phosphorylation rhythm in a wide range of Kai protein concentrations, KaiA and KaiB were found to be “parameter-tuning” and “state-switching” regulators of KaiC phosphorylation rhythm, respectively. Our results also suggest a possible entrainment mechanism of the cellular circadian clock with the circadian variation of intracellular levels of Kai proteins.

Keywords: Circadian clock, Cyanobacterium, KaiC phosphorylation rhythm, Entrainment

Division of Biological Science, Graduate School of Science, Nagoya University and CREST, Japan Science and Technology Agency (JST), Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan

Corresponding author. Fax: +81 52 789 2963.

1 These authors contributed equally to this work.

2 Present address: Laboratory for Systems Biology, RIKEN Center for Developmental Biology, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan.

3 Present address: Division of Advanced Sciences, Ochadai Academic Production, Ochanomizu University, 2-1-1 Ohtsuka, Bunkyo-ku, Tokyo 112-8610, Japan.

PII: S0014-5793(10)00035-9

doi:10.1016/j.febslet.2010.01.016

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