Nucleotide binding and autophosphorylation of the clock protein KaiC as a circadian timing process of cyanobacteria

Taeko Nishiwaki, Hideo Iwasaki, Masahiro Ishiura, Takao Kondo

Research output: Contribution to journalArticle

142 Citations (Scopus)


A negative feedback control of kaiC expression by KaiC protein has been proposed to generate a basic oscillation of the circadian clock in the cyanobacterium Synechococcus sp. PCC 7942. KaiC has two P loops or Walker's motif As, that are potential ATP-/GTP-binding motifs and DXXG motifs conserved in various GTP-binding proteins. Herein, we demonstrate that in vitro KaiC binds ATP and, with lower affinity, GTP. Point mutation by site- directed mutagenesis of P loop 1 completely nullified the circadian rhythm of kaiBC expression and markedly reduced ATP-binding activity. Moreover, KaiC can be autophosphorylated in vitro. These results suggest that the nucleotide-binding activity of KaiC plays important roles in the generation of circadian oscillation in cyanobacteria.

Original languageEnglish
Pages (from-to)495-499
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number1
Publication statusPublished - 2000 Jan 4


ASJC Scopus subject areas

  • General

Cite this