A model for the circadian rhythm of cyanobacteria that maintains oscillation without gene expression.
An intriguing property of the cyanobacterial circadian clock is that endogenous rhythm persists when protein abundances are kept constant either in the presence of translation and transcription inhibitors or in the constant dark condition. Here we propose a regulatory mechanism of KaiC phosphorylation for the generation of circadian oscillations in cyanobacteria. In the model, clock proteins KaiA and KaiB are assumed to have multiple states, regulating the KaiC phosphorylation process. The model can explain 1), the sustained oscillation of gene expression and protein abundance when the expression of the kaiBC gene is regulated by KaiC protein, and 2), the sustained oscillation of phosphorylated KaiC when transcription and translation processes are inhibited and total protein abundance is fixed. Results of this work suggest that KaiA and KaiB strengthen the nonlinearity of KaiC phosphorylation, thereby promoting the circadian rhythm in cyanobacteria.
Kurosawa
Gen
G
Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan. kurosawa@aihara.jst.go.jp
Aihara
Kazuyuki
K
Iwasa
Yoh
Y
D001426:Bacterial Proteins / Q000378:metabolism*; D002940:Circadian Rhythm; D056925:Circadian Rhythm Signaling Peptides and Proteins; D000458:Cyanobacteria / Q000502:physiology*; D003624:Darkness; D015964:Gene Expression Regulation, Bacterial; D008027:Light; D008954:Models, Biological; D010766:Phosphorylation
D001426:Bacterial Proteins; D056925:Circadian Rhythm Signaling Peptides and Proteins; C114269:KaiA protein, cyanobacteria; C114270:KaiB protein, cyanobacteria; C114271:KaiC protein, cyanobacteria