title: Circadian formation of clock protein complexes by KaiA, KaiB, KaiC, and SasA in cyanobacteria.
abstract: Physical interactions among clock-related proteins KaiA, KaiB, KaiC, and SasA are proposed to be important for circadian function in the cyanobacterium Synechococcus elongatus PCC 7942. Here we show that the Kai proteins and SasA form heteromultimeric protein complexes dynamically in a circadian fashion. KaiC forms protein complexes of approximately 350 and 400-600 kDa during the subjective day and night, respectively, and serves as a core of the circadian protein complexes. This change in the size of the KaiC-containing complex is accompanied by nighttime-specific interaction of KaiA and KaiB with KaiC. In various arrhythmic mutants that lack each functional Kai protein or SasA, circadian rhythms in formation of the clock protein complex are abolished, and the size of the protein complexes is dramatically affected. Thus, circadian-regulated formation of the clock protein complexes is probably a critical process in the generation of circadian rhythm in cyanobacteria.
authors.affiliation: Division of Biological Science, Graduate School of Science, Nagoya University, Japan.
authors.forename: Hakuto
authors.initials: H
authors.lastname: Kageyama
authors.forename: Takao
authors.initials: T
authors.lastname: Kondo
authors.forename: Hideo
authors.initials: H
authors.lastname: Iwasaki
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism / Q000502:physiology*; D002850:Chromatography, Gel; D002940:Circadian Rhythm; D056925:Circadian Rhythm Signaling Peptides and Proteins; D000458:Cyanobacteria / Q000378:metabolism*; D019281:Dimerization; D015151:Immunoblotting; D008954:Models, Biological; D010770:Phosphotransferases; D011233:Precipitin Tests; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D056925:Circadian Rhythm Signaling Peptides and Proteins; C114269:KaiA protein, cyanobacteria; C114270:KaiB protein, cyanobacteria; C114271:KaiC protein, cyanobacteria; D012333:RNA, Messenger; D010770:Phosphotransferases; D011494:Protein Kinases; C083143:SasA protein, Synechococcus