title: KaiA-stimulated KaiC phosphorylation in circadian timing loops in cyanobacteria.
abstract: Cyanobacterial clock proteins KaiA and KaiC are proposed as positive and negative regulators in the autoregulatory circadian kaiBC expression, respectively. Here, we show that activation of kaiBC expression by kaiA requires KaiC, suggesting a positive feedback control in the cyanobacterial clockwork. We found that robust circadian phosphorylation of KaiC. KaiA was essential for in vivo KaiC phosphorylation and activated in vitro KaiC autophosphorylation. These effects of KaiA were attenuated by the kaiA2 long period mutation. Both the long period phenotype and the abnormal KaiC phosphorylation in this mutant were suppressed by a previously undocumented kaiC mutation. We propose that KaiA-stimulated circadian KaiC phosphorylation is important for circadian timing.
authors.affiliation: Division of Biological Science, Graduate School of Science, Nagoya University, and Core Research for Evolutional Science and Technology (CREST), Japan. iwasaki@bio.nagoya-u.ac.jp
authors.forename: Hideo
authors.initials: H
authors.lastname: Iwasaki
authors.forename: Taeko
authors.initials: T
authors.lastname: Nishiwaki
authors.forename: Yohko
authors.initials: Y
authors.lastname: Kitayama
authors.forename: Masato
authors.initials: M
authors.lastname: Nakajima
authors.forename: Takao
authors.initials: T
authors.lastname: Kondo
mesh_terms: D000483:Alleles; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D001683:Biological Clocks / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D056925:Circadian Rhythm Signaling Peptides and Proteins; D000458:Cyanobacteria / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D005246:Feedback; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D008163:Luminescent Measurements; D009154:Mutation; D010766:Phosphorylation; D017440:Photoperiod; D011499:Protein Processing, Post-Translational; D013489:Suppression, Genetic
chemical_list: D001426:Bacterial Proteins; D056925:Circadian Rhythm Signaling Peptides and Proteins; C114269:KaiA protein, cyanobacteria; C114271:KaiC protein, cyanobacteria