title: Structure and function from the circadian clock protein KaiA of Synechococcus elongatus: a potential clock input mechanism.
abstract: In the cyanobacterium Synechococcus elongatus (PCC 7942) the proteins KaiA, KaiB, and KaiC are required for circadian clock function. We deduced a circadian clock function for KaiA from a combination of biochemical and structural data. Both KaiA and its isolated carboxyl-terminal domain (KaiA180C) stimulated KaiC autophosphorylation and facilitated attenuation of KaiC autophosphorylation by KaiB. An amino-terminal domain (KaiA135N) had no function in the autophosphorylation assay. NMR structure determination showed that KaiA135N is a pseudo-receiver domain. We propose that this pseudo-receiver is a timing input-device that regulates KaiA stimulation of KaiC autophosphorylation, which in turn is essential for circadian timekeeping.
authors.affiliation: Department of Biology, Texas A&M University, College Station 77843, USA.
authors.forename: Stanly B
authors.initials: SB
authors.lastname: Williams
authors.forename: Ioannis
authors.initials: I
authors.lastname: Vakonakis
authors.forename: Susan S
authors.initials: SS
authors.lastname: Golden
authors.forename: Andy C
authors.initials: AC
authors.lastname: LiWang
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D001683:Biological Clocks / Q000235:genetics / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D056925:Circadian Rhythm Signaling Peptides and Proteins; D000458:Cyanobacteria / Q000235:genetics / Q000502:physiology*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D010766:Phosphorylation; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D012996:Solutions; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D056925:Circadian Rhythm Signaling Peptides and Proteins; C114269:KaiA protein, cyanobacteria; C114270:KaiB protein, cyanobacteria; C114271:KaiC protein, cyanobacteria; D011993:Recombinant Fusion Proteins; D012996:Solutions