Reconstitution of Circadian Oscillation of Cyanobacterial KaiC Phosphorylation in Vitro

Abstract

Kai proteins globally regulate circadian gene expression of cyanobacteria. The KaiC phosphorylation cycle, which persists even without transcription or translation, is assumed to be a basic timing process of the circadian clock. We have reconstituted the self-sustainable oscillation of KaiC phosphorylation in vitro by incubating KaiC with KaiA, KaiB, and adenosine triphosphate. The period of the in vitro oscillation was stable despite temperature change (temperature compensation), and the circadian periods observed in vivo in KaiC mutant strains were consistent with those measured in vitro. The enigma of the circadian clock can now be studied in vitro by examining the interactions between three Kai proteins.

The pseudo‐receiver domain of CikA regulates the cyanobacterial circadian input pathway

“…The importance of post-translational events in circadian regulation in S. elongatus was portrayed dramatically by the demonstration that a circadian rhythm of KaiC phosphorylation can occur in vitro when only KaiA, KaiB, KaiC and ATP are present (Nakajima et al, 2005). In the context of the cell, this core oscillation is integrated with other events that allow synchronization of the circadian oscillation (involving CikA) and relay of temporal information to clock-controlled processes.…”

“…The proteins of the cyanobacterial circadian oscillator, KaiA, KaiB and KaiC, have been identified and well studied at genetic, biochemical and structural levels (Golden, 2004;Iwasaki and Kondo, 2004;Nakajima et al ., 2005). Protein-protein interactions and the phosphorylation status of KaiC are two main principles of the central oscillator mechanism, and a circadian rhythm of KaiC phosphorylation can be established in vitro in a mixture of only KaiA, KaiB, KaiC and ATP (Nakajima et al ., 2005).…”

“…Protein-protein interactions and the phosphorylation status of KaiC are two main principles of the central oscillator mechanism, and a circadian rhythm of KaiC phosphorylation can be established in vitro in a mixture of only KaiA, KaiB, KaiC and ATP (Nakajima et al ., 2005). In the cyanobacterial cell the three oscillator components daily form a large complex, together with other components, that has been named the periodosome (Kageyama et al ., 2003;Golden, 2004;Iwasaki and Kondo, 2004).…”

A simple molecular mathematical model of mammalian hibernation

“…This is in striking contrast to research on circadian rhythms, which has a large and rapidly growing literature of models that span the metazoans (Forger and Peskin, 2003;Leise and Siegelmann, 2006;Nakajima et al, 2005;Tyson et al, 1999). The difference is largely due to the ubiquity of circadian rhythms, in particular their presence in several invertebrate and vertebrate model organisms including mammals (Dunlap and Loros, 2004;Hardin, 2005;K.…”

Even a stopped clock tells the right time twice a day: circadian timekeeping in Drosophila

“…Thus, just three Cyanobacteria clock proteins are sufficient for generating accurate rhythms, and rhythmic transcriptional regulation is unnecessary [42].…”