Structural insights into a circadian oscillator.

Johnson CH, Egli M, Stewart PL
Science. 2008 322 (5902): 697-701

PMID: 18974343 · PMCID: PMC2588432 · DOI:10.1126/science.1150451

An endogenous circadian system in cyanobacteria exerts pervasive control over cellular processes, including global gene expression. Indeed, the entire chromosome undergoes daily cycles of topological changes and compaction. The biochemical machinery underlying a circadian oscillator can be reconstituted in vitro with just three cyanobacterial proteins, KaiA, KaiB, and KaiC. These proteins interact to promote conformational changes and phosphorylation events that determine the phase of the in vitro oscillation. The high-resolution structures of these proteins suggest a ratcheting mechanism by which the KaiABC oscillator ticks unidirectionally. This posttranslational oscillator may interact with transcriptional and translational feedback loops to generate the emergent circadian behavior in vivo. The conjunction of structural, biophysical, and biochemical approaches to this system reveals molecular mechanisms of biological timekeeping.

MeSH Terms (14)

Bacterial Proteins Biological Clocks Cell Division Chromosomes, Bacterial Circadian Rhythm Circadian Rhythm Signaling Peptides and Proteins Dimerization Models, Molecular Phosphorylation Promoter Regions, Genetic Protein Biosynthesis Protein Conformation Synechococcus Transcription, Genetic

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