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.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Bacterial Proteins / chemistry
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Bacterial Proteins / genetics
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Bacterial Proteins / physiology*
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Biological Clocks / genetics
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Biological Clocks / physiology*
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Circadian Rhythm / physiology*
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Circadian Rhythm Signaling Peptides and Proteins
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Cyanobacteria / genetics
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Cyanobacteria / physiology*
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Models, Molecular
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Nuclear Magnetic Resonance, Biomolecular
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Phosphorylation
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Protein Conformation
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Protein Processing, Post-Translational
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Protein Structure, Tertiary
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Recombinant Fusion Proteins / chemistry
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Recombinant Fusion Proteins / physiology
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Sequence Homology, Amino Acid
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Solutions
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Structure-Activity Relationship
Substances
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Bacterial Proteins
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Circadian Rhythm Signaling Peptides and Proteins
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KaiA protein, cyanobacteria
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KaiB protein, cyanobacteria
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KaiC protein, cyanobacteria
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Recombinant Fusion Proteins
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Solutions