ATPase activity and its temperature compensation of the cyanobacterial clock protein KaiC

Genes Cells. 2008 Apr;13(4):387-95. doi: 10.1111/j.1365-2443.2008.01174.x.


KaiA, KaiB and KaiC constitute the circadian clock machinery in cyanobacteria. KaiC is a homohexamer; its subunit contains duplicated halves, each with a set of ATPase motifs. Here, using highly purified KaiC preparations of the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1 produced in Escherichia coli, we found that the N- and C-terminal domains of KaiC had extremely weak ATPase activity. ATPase activity showed temperature compensation in wild-type KaiC, but not in KaiC(S431A/T432A), a mutant that lacks two phosphorylation sites. We concluded that KaiC phosphorylation is involved in the ATPase temperature-compensation mechanism-which is probably critical to the stability of the circadian clock in cyanobacteria-and we hypothesized the following temperature-compensation mechanism: (i) The C-terminal phosphorylation sites of a KaiC hexamer subunit are phosphorylated by the C-terminal domain of an adjacent KaiC subunit; (ii) the phosphorylation suppresses the ATPase activity of the C-terminal domain; and (iii) the phosphorylated KaiC spontaneously dephosphorylates, resulting in the recover of ATPase activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / chemistry
  • Adenosine Triphosphatases / genetics
  • Adenosine Triphosphatases / metabolism*
  • Amino Acid Substitution
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Circadian Rhythm
  • Circadian Rhythm Signaling Peptides and Proteins
  • Cyanobacteria / genetics
  • Cyanobacteria / metabolism*
  • Kinetics
  • Models, Molecular
  • Mutagenesis, Site-Directed
  • Protein Structure, Tertiary
  • Protein Subunits
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Temperature


  • Bacterial Proteins
  • Circadian Rhythm Signaling Peptides and Proteins
  • KaiA protein, cyanobacteria
  • KaiC protein, cyanobacteria
  • Protein Subunits
  • Recombinant Proteins
  • Adenosine Triphosphatases