KaiB functions as an attenuator of KaiC phosphorylation in the cyanobacterial circadian clock system.
In the cyanobacterium Synechococcus elongatus PCC 7942, the KaiA, KaiB and KaiC proteins are essential for generation of circadian rhythms. We quantitatively analyzed the intracellular dynamics of these proteins and found a circadian rhythm in the membrane/cytosolic localization of KaiB, such that KaiB interacts with a KaiA-KaiC complex during the late subjective night. KaiB-KaiC binding is accompanied by a dramatic reduction in KaiC phosphorylation and followed by dissociation of the clock protein complex(es). KaiB attenuated KaiA-enhanced phosphorylation both in vitro and in vivo. Based on these results, we propose a novel role for KaiB in a regulatory link among subcellular localization, protein-protein interactions and post-translational modification of Kai proteins in the cyanobacterial clock system.
Division of Biological Science, Graduate School of Science, Nagoya University and CREST, Japan Science and Technology Corporation (JST), Furo-cho, Chikusa, Nagoya 464-8602, Japan.
Yohko
Y
Kitayama
Hideo
H
Iwasaki
Taeko
T
Nishiwaki
Takao
T
Kondo
D001426:Bacterial Proteins / Q000378:metabolism / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D056925:Circadian Rhythm Signaling Peptides and Proteins; D000458:Cyanobacteria / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation
D001426:Bacterial Proteins; D056925:Circadian Rhythm Signaling Peptides and Proteins; C114270:KaiB protein, cyanobacteria; C114271:KaiC protein, cyanobacteria