The Kai-Protein Clock—Keeping Track of Cyanobacteria’s Daily Life

The Kai system in cyanobacteria consists of three proteins: KaiA, KaiB, and KaiC, which regulate circadian rhythms.

• Cyanobacteria possess a circadian clock that relies on a protein-based mechanism rather than transcription-translation feedback.
• The Kai system is integral to the circadian rhythms of gene expression in cyanobacterial cells.
• Different cyanobacterial species exhibit variability in kai gene arrangements, with some having multiple copies and others like marine Prochlorococcus strains containing only kaiBC.
• Recent findings reveal the genomic distribution of kai genes across Bacteria and Archaea.
• The evolution of the Kai system is still being explored, with various hypotheses proposed regarding its development.

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