KaiB functions as an attenuator of KaiC phosphorylation in the cyanobacterial circadian clock system

Yohko Kitayama, Hideo Iwasaki, Taeko Nishiwaki, Takao Kondo

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202 Citations (Scopus)


In the cyanobacterium Synechococcus elongatus PCC 7942, the KaiA, KaiB and KaiC proteins are essential for generation of circadian rhythms. We quantitatively analyzed the intracellular dynamics of these proteins and found a circadian rhythm in the membrane/cytosolic localization of KaiB, such that KaiB interacts with a KaiA-KaiC complex during the late subjective night. KaiB-KaiC binding is accompanied by a dramatic reduction in KaiC phosphorylation and followed by dissociation of the clock protein complex(es). KaiB attenuated KaiA-enhanced phosphorylation both in vitro and in vivo. Based on these results, we propose a novel role for KaiB in a regulatory link among subcellular localization, protein-protein interactions and post-translational modification of Kai proteins in the cyanobacterial clock system.

Original languageEnglish
Pages (from-to)2127-2134
Number of pages8
JournalEMBO Journal
Issue number9
Publication statusPublished - 2003 May 1



  • Circadian clock
  • Cyanobacteria
  • KaiB
  • KaiC phosphorylation
  • Localization

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)

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