KaiA-stimulated KaiC phosphorylation in circadian timing loops in cyanobacteria

Hideo Iwasaki*, Taeko Nishiwaki, Yohko Kitayama, Masato Nakajima, Takao Kondo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

232 Citations (Scopus)


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 KaiAstimulated circadian KaiC phosphorylation is important for circadian timing.

Original languageEnglish
Pages (from-to)15788-15793
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number24
Publication statusPublished - 2002 Nov 26
Externally publishedYes

ASJC Scopus subject areas

  • General


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