ATPase activity of KaiC determines the basic timing for circadian clock of cyanobacteria
- Kazuki Terauchi,
- Yohko Kitayama,
- Taeko Nishiwaki,
- Kumiko Miwa,
- Yoriko Murayama,
- Tokitaka Oyama, and
- Takao Kondo*
- Division of Biological Science, Graduate School of Science, Nagoya University, Solution-Oriented Research for Science and Technology, Japan Science and Technology Agency, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
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Edited by Robert Haselkorn, University of Chicago, Chicago, IL, and approved August 17, 2007 (received for review July 5, 2007)
Abstract
Self-sustainable oscillation of KaiC phosphorylation has been reconstituted in vitro, demonstrating that this cycle is the basic time generator of the circadian clock of cyanobacteria. Here we show that the ATPase activity of KaiC satisfies the characteristics of the circadian oscillation, the period length, and the temperature compensation. KaiC possesses extremely weak but stable ATPase activity (15 molecules of ATP per day), and the addition of KaiA and KaiB makes the activity oscillate with a circadian period in vitro. The ATPase activity of KaiC is inherently temperature-invariant, suggesting that temperature compensation of the circadian period could be driven by this simple biochemical reaction. Moreover, the activities of wild-type KaiC and five period-mutant proteins are directly proportional to their in vivo circadian frequencies, indicating that the ATPase activity defines the circadian period. Thus, we propose that KaiC ATPase activity constitutes the most fundamental reaction underlying circadian periodicity in cyanobacteria.
Footnotes
- *To whom correspondence should be addressed. E-mail: kondo{at}bio.nagoya-u.ac.jp
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Author contributions: K.T. and Y.K. contributed equally to this work; K.T., Y.K., and T.K. designed research; K.T., Y.K., T.N., K.M., and Y.M. performed research; K.T., Y.K., T.N., T.O., and T.K. analyzed data; and K.T. and T.K. wrote the paper.
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The authors declare no conflict of interest.
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This article is a PNAS Direct Submission.
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This article contains supporting information online at www.pnas.org/cgi/content/full/0706292104/DC1.
- © 2007 by The National Academy of Sciences of the USA
