KaiC intersubunit communication facilitates robustness of circadian rhythms in cyanobacteria

Kitayama, Yohko; Nishiwaki‐Ohkawa, Taeko; Sugisawa, Yukiko; Kondo, Takao

doi:10.1038/ncomms3897

Cited by 43 publications

(44 citation statements)

References 62 publications

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“…Similar active site configurations in KaiC and F 1 -ATPase and the aforementioned lack of large conformational changes between the kinase and "phosphatase" states of KaiC are also in line with the ATP synthase mechanism of dephosphorylation (47). Lastly, hexameric assembly and kinase, ATP synthase, and ATPase all mapping to the same active sites at CII subunit interfaces are consistent with allosteric control of KaiA-stimulated KaiC phosphorylation (38) and with communication and cooperative effects between KaiC protomers (54).…”

Section: Kaic Architecturesupporting

confidence: 49%

“…However, gold labeling gave a clear answer, and these experiments were carried out with full-length KaiB and KaiC proteins from S. elongatus (55) that constitute the in vitro PTO together with KaiA and ATP/Mg 2ϩ . That KaiC His 6 tags may have introduced an artifact is unlikely because C-terminally His-tagged KaiC was used to reconstitute the PTO in the same fashion as WT KaiC (54). The earliest evidence for CII binding actually came from native PAGE experiments that used KaiB with full-length KaiC (Fig.…”

Section: Evidence That Supports Binding Of Kaib To Kaiciimentioning

confidence: 99%

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Intricate Protein-Protein Interactions in the Cyanobacterial Circadian Clock

Egli

2014

Journal of Biological Chemistry

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Section: Kaic Architecturesupporting

confidence: 49%

Section: Evidence That Supports Binding Of Kaib To Kaiciimentioning

confidence: 99%

Intricate Protein-Protein Interactions in the Cyanobacterial Circadian Clock

Egli

2014

Journal of Biological Chemistry

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“…However, it is not fully understood how these conformational changes enhance the reversal of autophosphorylation. Recently, we revealed that substitution of the catalytic carboxylates E77 and E78 to glutamine residues, which decreases the ATPase activity of CI, does not affect the profile of autodephosphorylation (23). Therefore, it is unlikely that these conformational changes facilitate the coupling of ATP hydrolysis in CI to formation of ATP by reversing autodephosphorylation in CII.…”

Section: Discussionmentioning

confidence: 99%

Exchange of ADP with ATP in the CII ATPase domain promotes autophosphorylation of cyanobacterial clock protein KaiC

Nishiwaki‐Ohkawa

Kitayama

Ochiai

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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The cyanobacterial circadian oscillator can be reconstituted in vitro. In the presence of KaiA and KaiB, the phosphorylation state of KaiC oscillates with a periodicity of ∼24 h. KaiC is a hexameric P-loop ATPase with autophosphorylation and autodephosphorylation activities. Recently, we found that dephosphorylation of KaiC occurs via reversal of the phosphorylation reaction: a phosphate group attached to Ser431/Thr432 is transferred to KaiC-bound ADP to generate ATP, which is subsequently hydrolyzed. This unusual reaction mechanism suggests that the KaiC phosphorylation rhythm is sustained by periodic shifts in the equilibrium of the reversible autophosphorylation reaction, the molecular basis of which has never been elucidated. Because KaiC-bound ATP and ADP serve as substrates for the forward and reverse reactions, respectively, we investigated the regulation of the nucleotide-bound state of KaiC. In the absence of KaiA, the condition in which the reverse reaction proceeds, KaiC favored the ADP-bound state. KaiA increased the ratio of ATP to total KaiC-bound nucleotides by facilitating the release of bound ADP and the incorporation of exogenous ATP, allowing the forward reaction to proceed. When both KaiA and KaiB were present, the ratio of ATP to total bound nucleotides exhibited a circadian rhythm, whose phase was advanced by several hours relative to that of the phosphorylation rhythm. Based on these findings, we propose that the direction of the reversible autophosphorylation reaction is regulated by KaiA and KaiB at the level of substrate availability and that this regulation sustains the oscillation of the phosphorylation state of KaiC.in vitro reconstitution | self-sustained oscillation | nucleotide exchange

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“…Each KaiC protomer follows a cycle comprising the four steps in the presence of interactions among hexamer subunits and between hexamers. Therefore, the reaction rate of each step can be affected by the phosphorylation of other KaiC protomers within the same hexamer or by another KaiC hexamer through competition for free KaiA (38). If the cycle of each KaiC phosphorylation proceeds synchronously, the ratio of KaiC phosphorylation oscillates with large amplitude.…”

Section: Discussionmentioning

confidence: 99%

Low temperature nullifies the circadian clock in cyanobacteria through Hopf bifurcation

Murayama

Kori

Oshima

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Cold temperatures lead to nullification of circadian rhythms in many organisms. Two typical scenarios explain the disappearance of rhythmicity: the first is oscillation death, which is the transition from self-sustained oscillation to damped oscillation that occurs at a critical temperature. The second scenario is oscillation arrest, in which oscillation terminates at a certain phase. In the field of nonlinear dynamics, these mechanisms are called the Hopf bifurcation and the saddle-node on an invariant circle bifurcation, respectively. Although these mechanisms lead to distinct dynamical properties near the critical temperature, it is unclear to which scenario the circadian clock belongs. Here we reduced the temperature to dampen the reconstituted circadian rhythm of phosphorylation of the recombinant cyanobacterial clock protein KaiC. The data led us to conclude that Hopf bifurcation occurred at ∼19°C. Below this critical temperature, the self-sustained rhythms of KaiC phosphorylation transformed to damped oscillations, which are predicted by the Hopf bifurcation theory. Moreover, we detected resonant oscillations below the critical temperature when temperature was periodically varied, which was reproduced by numerical simulations. Our findings suggest that the transition to a damped oscillation through Hopf bifurcation contributes to maintaining the circadian rhythm of cyanobacteria through resonance at cold temperatures.

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KaiC intersubunit communication facilitates robustness of circadian rhythms in cyanobacteria

Cited by 43 publications

References 62 publications

Intricate Protein-Protein Interactions in the Cyanobacterial Circadian Clock

Intricate Protein-Protein Interactions in the Cyanobacterial Circadian Clock

Exchange of ADP with ATP in the CII ATPase domain promotes autophosphorylation of cyanobacterial clock protein KaiC

Low temperature nullifies the circadian clock in cyanobacteria through Hopf bifurcation

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