Detecting KaiC phosphorylation rhythms of the cyanobacterial circadian oscillator in vitro and in vivo

Yong Ick Kim, Joseph S. Boyd, Javier Espinosa, Susan S. Golden

Research output: Chapter in Book/Report/Conference proceedingChapter

20 Scopus citations


The central oscillator of the cyanobacterial circadian clock is unique in the biochemical simplicity of its components and the robustness of the oscillation. The oscillator is composed of three cyanobacterial proteins: KaiA, KaiB, and KaiC. If very pure preparations of these three proteins are mixed in a test tube in the right proportions and with ATP and MgCl2, the phosphorylation states of KaiC will oscillate with a circadian period, and these states can be analyzed simply by SDS-PAGE. The purity of the proteins is critical for obtaining robust oscillation. Contaminating proteases will destroy oscillation by degradation of Kai proteins, and ATPases will attenuate robustness by consumption of ATP. Here, we provide a detailed protocol to obtain pure recombinant proteins from Escherichia coli to construct a robust cyanobacterial circadian oscillator in vitro. In addition, we present a protocol that facilitates analysis of phosphorylation states of KaiC and other phosphorylated proteins from in vivo samples.

Original languageEnglish (US)
Title of host publicationMethods in Enzymology
PublisherAcademic Press Inc.
Number of pages21
StatePublished - 2015
Externally publishedYes

Publication series

NameMethods in Enzymology
ISSN (Print)0076-6879
ISSN (Electronic)1557-7988

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology


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