A protein fold switch joins the circadian oscillator to clock output in cyanobacteria

Yong Gang Chang, Susan E. Cohen, Connie Phong, William K. Myers, Yong Ick Kim, Roger Tseng, Jenny Lin, Li Zhang, Joseph S. Boyd, Yvonne Lee, Shannon Kang, David Lee, Sheng Li, R. David Britt, Michael J. Rust, Susan S. Golden, Andy Li Wang

Research output: Contribution to journalArticlepeer-review

137 Scopus citations


Organisms are adapted to the relentless cycles of day and night, because they evolved timekeeping systems called circadian clocks, which regulate biological activities with ∼24-hour rhythms. The clock of cyanobacteria is driven by a three-protein oscillator composed of KaiA, KaiB, and KaiC, which together generate a circadian rhythm of KaiC phosphorylation. We show that KaiB flips between two distinct three-dimensional folds, and its rare transition to an active state provides a time delay that is required to match the timing of the oscillator to that of Earth's rotation. Once KaiB switches folds, it binds phosphorylated KaiC and captures KaiA, which initiates a phase transition of the circadian cycle, and it regulates components of the clock-output pathway, which provides the link that joins the timekeeping and signaling functions of the oscillator.

Original languageEnglish (US)
Pages (from-to)324-328
Number of pages5
Issue number6245
StatePublished - Jul 17 2015
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General


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