Physical interactions among circadian clock proteins KaiA, KaiB and KaiC in cyanobacteria

Hideo Iwasaki, Yasuhito Taniguchi, Masahiro Ishiura, Takao Kondo

Research output: Contribution to journalArticle

131 Citations (Scopus)


The kai gene cluster, which is composed of three genes, kaiA, kaiB and kaiC, is essential for the generation of circadian rhythms in the unicellular cyanobacterium Synechococcus sp. strain PCC 7942. Here we demonstrate the direct association of KaiA, KaiB and KaiC in yeast cells using the two-hybrid system, in vitro and in cyanobacterial cells. KaiC enhanced KaiA-KaiB interaction in vitro and in yeast cells, suggesting that the three Kai proteins were able to form a heteromultimeric complex. We also found that a long period mutation kaiA1 dramatically enhanced KaiA-KaiB interaction in vitro. Thus, direct protein-protein association among the Kai proteins may be a critical process in the generation of circadian rhythms in cyanobacteria.

Original languageEnglish
Pages (from-to)1137-1145
Number of pages9
JournalEMBO Journal
Issue number5
Publication statusPublished - 1999 Mar 1
Externally publishedYes



  • Circadian rhythm
  • Kai genes
  • Protein-protein interaction
  • Synechococcus

ASJC Scopus subject areas

  • Genetics
  • Cell Biology

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