title: Nucleotide binding and autophosphorylation of the clock protein KaiC as a circadian timing process of cyanobacteria.
abstract: A negative feedback control of kaiC expression by KaiC protein has been proposed to generate a basic oscillation of the circadian clock in the cyanobacterium Synechococcus sp. PCC 7942. KaiC has two P loops or Walker's motif As, that are potential ATP-/GTP-binding motifs and DXXG motifs conserved in various GTP-binding proteins. Herein, we demonstrate that in vitro KaiC binds ATP and, with lower affinity, GTP. Point mutation by site-directed mutagenesis of P loop 1 completely nullified the circadian rhythm of kaiBC expression and markedly reduced ATP-binding activity. Moreover, KaiC can be autophosphorylated in vitro. These results suggest that the nucleotide-binding activity of KaiC plays important roles in the generation of circadian oscillation in cyanobacteria.
authors.affiliation: Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Nishiwaki
authors.forename: H
authors.initials: H
authors.lastname: Iwasaki
authors.forename: M
authors.initials: M
authors.lastname: Ishiura
authors.forename: T
authors.initials: T
authors.lastname: Kondo
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001683:Biological Clocks / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D056925:Circadian Rhythm Signaling Peptides and Proteins; D000458:Cyanobacteria / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006160:Guanosine Triphosphate / Q000378:metabolism; D008163:Luminescent Measurements; D016297:Mutagenesis, Site-Directed; D009711:Nucleotides / Q000378:metabolism*; D010766:Phosphorylation; D017354:Point Mutation; D011485:Protein Binding; D014466:Ultraviolet Rays
chemical_list: D001426:Bacterial Proteins; D056925:Circadian Rhythm Signaling Peptides and Proteins; C114271:KaiC protein, cyanobacteria; D009711:Nucleotides; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate