Structure and function from the circadian clock protein KaiA of Synechococcus elongatus: a potential clock input mechanism

Proc Natl Acad Sci U S A. 2002 Nov 26;99(24):15357-62. doi: 10.1073/pnas.232517099. Epub 2002 Nov 15.

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

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

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

Substances

  • Bacterial Proteins
  • Circadian Rhythm Signaling Peptides and Proteins
  • KaiA protein, cyanobacteria
  • KaiB protein, cyanobacteria
  • KaiC protein, cyanobacteria
  • Recombinant Fusion Proteins
  • Solutions