Related Experiment Video
Updated: Aug 7, 2026

Rapid Analysis of Circadian Phenotypes in Arabidopsis Protoplasts Transfected with a Luminescent Clock Reporter
Published on: September 17, 2016
Cyanobacterial circadian pacemaker: Kai protein complex dynamics in the KaiC phosphorylation cycle in vitro
Hakuto Kageyama1, Taeko Nishiwaki, Masato Nakajima
1Division of Biological Science, Graduate School of Science, Nagoya University and CREST & SORST, Japan Science and Technology Corporation, Furo-cho 1, Chikusa, Nagoya 464-8602, Japan.
Abstract:
KaiA, KaiB, and KaiC are essential proteins of the circadian clock in the cyanobacterium Synechococcus elongatus PCC 7942. The phosphorylation cycle of KaiC that occurs in vitro after mixing the three proteins and ATP is thought to be the master oscillation governing the circadian system. We analyzed the temporal profile of complexes formed between the three Kai proteins. In the phosphorylation phase, KaiA actively and repeatedly associated with KaiC to promote KaiC phosphorylation. High levels of phosphorylation of KaiC induced the association of the KaiC hexamer with KaiB and inactivate KaiA to begin the dephosphorylation phase, which is closely linked to shuffling of the monomeric KaiC subunits among the hexamer. By reducing KaiC phosphorylation, KaiB dissociated from KaiC, reactivating KaiA. We also confirmed that a similar model can be applied in cyanobacterial cells. The molecular model proposed here provides mechanisms for circadian timing systems.
More Related Videos
10:33Flexible Measurement of Bioluminescent Reporters Using an Automated Longitudinal Luciferase Imaging Gas- and Temperature-optimized Recorder (ALLIGATOR)
Published on: December 13, 2017
11:56In Vitro Bioluminescence Assay to Characterize Circadian Rhythm in Mammary Epithelial Cells
Published on: September 28, 2017
Related Concept Videos
Circadian Rhythms and Gene Regulation
Calmodulin-dependent Signaling
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
Positive Regulator Molecules
Positive Regulator Molecules
Biological Clocks and Seasonal Responses
M-Cdk Drives Transition Into Mitosis
Cyclin-dependent kinases, or Cdks, work in concert with cyclins to control cell cycle transitions. M-Cdk, a complex of Cdk1 bound to M cyclin, is a well-known example of this coordinated control that drives the transition from the G2 to the M phase.
M cyclin...