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

• Autores: Yong-Gang Chang, Susan E. Cohen, Connie Phong
• Localización: Science, ISSN 0036-8075, Vol. 349, Nº 6245, 2015, págs. 324-328
• Idioma: inglés
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• Resumen

  • 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.