Abstract
This review summarizes recent advances in understanding the cyanobacterial circadian clock, emphasizing how the KaiA, KaiB, and KaiC proteins generate robust, temperature-compensated rhythms through ordered phosphorylation, conformational switching, and dynamic protein interactions. A comparative analysis of 30 KaiC structures under different states of phosphorylation and nucleotide binding is also presented. Together, these structural and mechanistic insights illuminate fundamental principles of biological timekeeping and evolutionary adaptations in these photosynthetic prokaryotes.