KaiA-stimulated KaiC phosphorylation in circadian timing loops in cyanobacteria
- Division of Biological Science, Graduate School of Science, Nagoya University, and Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Corporation (JST), Furo-cho, Chikusa, Nagoya 464-8602, Japan
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Edited by Robert Haselkorn, University of Chicago, Chicago, IL, and approved September 12, 2002 (received for review August 5, 2002)
Abstract
Cyanobacterial clock proteins KaiA and KaiC are proposed as positive and negative regulators in the autoregulatory circadian kaiBC expression, respectively. Here, we show that activation of kaiBC expression by kaiA requires KaiC, suggesting a positive feedback control in the cyanobacterial clockwork. We found that robust circadian phosphorylation of KaiC. KaiA was essential for in vivo KaiC phosphorylation and activated in vitro KaiC autophosphorylation. These effects of KaiA were attenuated by the kaiA2 long period mutation. Both the long period phenotype and the abnormal KaiC phosphorylation in this mutant were suppressed by a previously undocumented kaiC mutation. We propose that KaiA-stimulated circadian KaiC phosphorylation is important for circadian timing.
Footnotes
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↵ * H.I. and T.N. contributed equally to this work.
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↵ † To whom correspondence should be addressed. E-mail: iwasaki{at}bio.nagoya-u.ac.jp or kondo{at}bio.nagoya-u.ac.jp.
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This paper was submitted directly (Track II) to the PNAS office.
- Abbreviations:
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λPPase, λ phosphatase
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LL, continuous illumination
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CBB, Coomassie brilliant blue
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- Copyright © 2002, The National Academy of Sciences
