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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.

Original publication

DOI

10.1073/pnas.232517099

Type

Journal article

Journal

Proc Natl Acad Sci U S A

Publication Date

26/11/2002

Volume

99

Pages

15357 - 15362

Keywords

Bacterial Proteins, Biological Clocks, Circadian Rhythm, Circadian Rhythm Signaling Peptides and Proteins, Cyanobacteria, Models, Molecular, Nuclear Magnetic Resonance, Biomolecular, Phosphorylation, Protein Conformation, Protein Processing, Post-Translational, Protein Structure, Tertiary, Recombinant Fusion Proteins, Sequence Homology, Amino Acid, Solutions, Structure-Activity Relationship