Cyanobacterial circadian clockwork: roles of KaiA, KaiB and the kaiBC promoter in regulating KaiC

Circadian clocks in cyanobacteria may operate differently from those in eukaryotes, with phosphorylation status of the clock protein KaiC playing a crucial role.

• Some features of circadian clocks are conserved between prokaryotic cyanobacteria and eukaryotes, while others differ.
• The circadian autoregulatory feedback loop in cyanobacteria does not depend on specific clock gene promoters, unlike in eukaryotes.
• A heterologous promoter can effectively replace the kaiBC promoter in cyanobacteria.
• KaiC is phosphorylated in living organisms, similar to eukaryotic clock proteins.
• KaiA and KaiB regulate KaiC phosphorylation, with KaiA inhibiting dephosphorylation and KaiB counteracting KaiA's effect.
• The circadian period in cyanobacteria is influenced by both the phosphorylation status of KaiC and its degradation rate.

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