The day/night switch in KaiC, a central oscillator component of the circadian clock of cyanobacteria

Kim, Yong Ick; Dong, Guojun; Carruthers, Carl W.; Golden, Susan S.; LiWang, Andy

doi:10.1073/pnas.0800526105

Cited by 132 publications

(205 citation statements)

References 43 publications

Supporting

Mentioning

194

Contrasting

Order By: Relevance

“…1A, the phosphorylation profiles of KaiC in the presence and absence of KaiA and KaiB were the same as those published on the S. elongatus homologs (20,(40)(41)(42): KaiA induced autophosphorylation of KaiC, whereas KaiC alone or in the sole presence of KaiB autodephosphorylated. The role of KaiB is to inhibit KaiA, but only after KaiC becomes hyperphosphorylated.…”

supporting

confidence: 66%

“…1B are the KaiA-induced phosphorylation profiles of KaiC-AT, KaiC-SE, KaiC-SA, and KaiC-ET, where X and Y in KaiC-XY represent the amino acyl residues at positions 431 and 432, respectively. Alanyl and glutamyl substitutions at these positions have been shown to mimic, respectively, the dephosphorylated and phosphorylated states of S431 and T432 (16,20,23). KaiA-induced autophosphorylation of KaiC-AT and KaiC-SE, respectively, mimicked the reactions ST → SpT and SpT → pSpT, whereas that of KaiC-SA and KaiC-ET mimicked the ST → pST and pST → pSpT reactions.…”

mentioning

confidence: 99%

“…The A loops of free KaiC are in a dynamic equilibrium that favors the buried positions, thereby maintaining KaiC in a hypophosphorylated state (20). KaiA selectively captures the A loops of KaiC in their exposed positions, thereby shifting the population of KaiC proteins to autophosphorylate (ST → SpT → pSpT) (20)(21)(22). However, the allosteric mechanism by which A-loop exposure activates autophosphorylation at sites >15 Å away was unclear.…”

mentioning

confidence: 99%

“…KaiC is a twodomain homohexamer, with each domain forming a ring (19). The A loops of free KaiC are in a dynamic equilibrium that favors the buried positions, thereby maintaining KaiC in a hypophosphorylated state (20). KaiA selectively captures the A loops of KaiC in their exposed positions, thereby shifting the population of KaiC proteins to autophosphorylate (ST → SpT → pSpT) (20)(21)(22).…”

mentioning

confidence: 99%

“…Insights into the destabilizing effect of phospho-T432 on the CII ring can be obtained from the crystal structures of KaiC (26). Although phospho-T432 appears to form stabilizing intersubunit interactions with R385 (26), its phosphate group may also have repulsive intersubunit interactions with E318 and, to a lesser extent, with D417 (SI Appendix, The A loops of KaiC (residues 487-497) exist in a dynamic equilibrium between buried and exposed positions, the latter of which promotes KaiC autophosphorylation and the former of which promotes autodephosphorylation (20). In the absence of KaiA binding, the equilibrium is toward the buried position, thereby maintaining KaiC in a hypophosphorylated state.…”

mentioning

confidence: 99%

See 4 more Smart Citations

Flexibility of the C-terminal, or CII, ring of KaiC governs the rhythm of the circadian clock of cyanobacteria

Chang

Kuo

Tseng

et al. 2011

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

Self Cite

144

View full text Add to dashboard Cite

In the cyanobacterial circadian oscillator, KaiA and KaiB alternately stimulate autophosphorylation and autodephosphorylation of KaiC with a periodicity of approximately 24 h. KaiA activates autophosphorylation by selectively capturing the A loops of KaiC in their exposed positions. The A loops and sites of phosphorylation, residues S431 and T432, are located in the CII ring of KaiC. We find that the flexibility of the CII ring governs the rhythm of KaiC autophosphorylation and autodephosphorylation and is an example of dynamics-driven protein allostery. KaiA-induced autophosphorylation requires flexibility of the CII ring. In contrast, rigidity is required for KaiC-KaiB binding, which induces a conformational change in KaiB that enables it to sequester KaiA by binding to KaiA's linker. Autophosphorylation of the S431 residues around the CII ring stabilizes the CII ring, making it rigid. In contrast, autophosphorylation of the T432 residues offsets phospho-S431-induced rigidity to some extent. In the presence of KaiA and KaiB, the dynamic states of the CII ring of KaiC executes the following circadian rhythm: CII ST flexible → CII SpT flexible → CII pSpT rigid → CII pST very-rigid → CII ST flexible . Apparently, these dynamic states govern the pattern of phosphorylation, ST → SpT → pSpT → pST → ST. CII-CI ring-on-ring stacking is observed when the CII ring is rigid, suggesting a mechanism through which the ATPase activity of the CI ring is rhythmically controlled. SasA, a circadian clock-output protein, binds to the CI ring. Thus, rhythmic ring stacking may also control clock-output pathways.

show abstract

supporting

confidence: 66%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Flexibility of the C-terminal, or CII, ring of KaiC governs the rhythm of the circadian clock of cyanobacteria

Chang

Kuo

Tseng

et al. 2011

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

Self Cite

144

View full text Add to dashboard Cite

show abstract

Circadian Programmes in Cyanobacteria

Johnson

2011

Encyclopedia of Life Sciences

View full text Add to dashboard Cite

Cyanobacteria are prokaryotes that express circadian (daily) rhythms. In rhythmic environments, the fitness of cyanobacteria is improved when this clock is operational and when its circadian period is similar to the period of the environmental cycle. In cyanobacteria, three key proteins (KaiA, KaiB and KaiC) form a core molecular clockwork that orchestrates global gene expression by modulating chromosomal topology. The three‐dimensional structures of these proteins have been determined. KaiA, KaiB and KaiC form a multiprotein nanomachine that can reconstitute a circadian oscillator in vitro , and this oscillator appears to function as a post‐translational oscillator (PTO) in vivo . Because this PTO regulates rhythmic transcription and translation, the entire circadian system comprises both the PTO and a transcriptional/translational feedback loop. Models of the complete in vivo system have important implications for our understanding of circadian clocks in higher organisms, including mammals. Key Concepts: Prokaryotic cyanobacteria have a circadian timekeeping system that enhances fitness. These cells exhibit pervasive circadian regulation of gene expression, possibly mediated by cyclic changes of chromosomal topology. A circadian rhythm of the phosphorylation of the central clock protein KaiC can be reconstituted in vitro with three proteins derived from cyanobacteria (KaiA, KaiB and KaiC) and ATP. KaiA, KaiB and KaiC are the only circadian clock proteins for which the 3‐D structure of full‐length proteins is known. Structural, biochemical and biophysical methods have been used to study the mechanism by which KaiC is rhythmically phosphorylated and dephosphorylated. Mathematical modelling that has been applied to the in vitro and in vivo systems indicate the existence of a core biochemical post‐translational oscillator (PTO) that controls a larger transcription/translation feedback loop (TTFL).

show abstract

Circadian Programmes in Cyanobacteria

Cohen

2021

Encyclopedia of Life Sciences

View full text Add to dashboard Cite

Cyanobacteria are bacteria that express circadian (daily) rhythms. In rhythmic environments, the fitness of cyanobacteria is improved when this clock is operational and when its circadian period is similar to the period of the environmental cycle. In cyanobacteria, three key proteins (KaiA, KaiB and KaiC) form a core molecular clockwork that orchestrates rhythmic outputs including global rhythms of gene expression, cell division, compaction of the chromosome and metabolism. KaiA, KaiB and KaiC form a multiprotein nanomachine that can reconstitute a circadian oscillator in vitro , and this oscillator appears to function as a posttranslational oscillator (PTO) in vivo . In vivo , an extended clock network allows the core oscillator to synchronize with the environment and relate temporal information to clock‐controlled activities. Models of the complete in vivo system have important implications for our understanding of circadian clocks in higher organisms, including mammals. Key Concepts Prokaryotic cyanobacteria have a circadian timekeeping system that enhances fitness. These cells exhibit pervasive circadian regulation of gene expression. A circadian rhythm of the phosphorylation of the central clock protein KaiC can be reconstituted in vitro with three proteins derived from cyanobacteria (KaiA, KaiB and KaiC) and ATP. KaiA, KaiB and KaiC are the only circadian clock proteins for which the 3D structure of full‐length proteins is known. Structural, biochemical and biophysical methods have been used to study the mechanism by which KaiC is rhythmically phosphorylated and dephosphorylated. Rhythmic associations of the extended clock network with the KaiABC oscillator help to coordinate rhythmic outputs.

show abstract

The day/night switch in KaiC, a central oscillator component of the circadian clock of cyanobacteria

Cited by 132 publications

References 43 publications

Flexibility of the C-terminal, or CII, ring of KaiC governs the rhythm of the circadian clock of cyanobacteria

Flexibility of the C-terminal, or CII, ring of KaiC governs the rhythm of the circadian clock of cyanobacteria

Circadian Programmes in Cyanobacteria

Circadian Programmes in Cyanobacteria

Contact Info

Product

Resources

About