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Residues E318 and E319 of KaiC protein are indispensable for its phosphorylation, with E318 providing catalytic function and E319 mediating Mg2+ coordination.

Molecular dynamics simulations revealed that mutations at residues 318 and 319 reduce the stability of the KaiC protein, particularly the CII domain, increase solvent accessibility of phosphorylation sites, weaken rigidity near the ATP-binding pocket, and disrupt the Mg2+ coordination network. The study concludes that efficient KaiC phosphorylation requires the catalytic function of E318 and the Mg2+ coordination mediation by E319, both of which are indispensable.

Last updated: Aug 25, 2026•0 RCTs•📖 Read as article →

Evidence Score

Evidence Score24/100
Human RCT☆☆☆☆☆
Meta-analysis☆☆☆☆☆
Mechanism★★★★★
Safety★★★★☆
Confidencelow

Study Evidence

Study 1. Regulation mechanism study of residues E318/319 for KaiC protein phosphorylation.

observational

Guo W, Zhao Y, Ke X, Feng H, Li A, Yan Y, Zhao Y · Biophysical journal (2026)

Participants: N/A
Duration: N/A
Intervention: Mutations at residues 318 and 319 of the KaiC protein (simulated via molecular dynamics)
Outcome: KaiC protein phosphorylation, protein stability, solvent accessibility of phosphorylation sites, rigidity near ATP-binding pocket, Mg2+ coordination network
Effect Size: N/A
Population: KaiC protein from cyanobacteria (in silico study)

Result:

PubMed: 42324775DOI: 10.1016/j.bpj.2026.06.023

Mechanism Graph

Mutations at E318/E319 reduce overall protein stability, especially in the CII domain
↓
Phosphorylation sites become more accessible to solvent
↓
Rigidity of residues near the ATP-binding pocket is weakened
↓
Mg2+ coordination network is disrupted
↓
Result: Phosphorylation is completely inhibited, as E318 is required for catalysis and E319 for Mg2+ coordination

Limitations

  • ⚠Study is based on molecular dynamics simulations, not experimental validation in vivo
  • ⚠Findings are specific to cyanobacterial KaiC and may not directly translate to human circadian clock proteins

Frequently Asked Questions

What is the role of residue E318 in KaiC phosphorylation?▼

E318 provides catalytic function essential for efficient phosphorylation of KaiC.

How does residue E319 contribute to KaiC phosphorylation?▼

E319 mediates the coordination of Mg2+, which is necessary for the phosphorylation reaction.

What happens when residues 318 and 319 are mutated?▼

Mutations at these residues completely inhibit KaiC phosphorylation by reducing protein stability, increasing solvent accessibility of phosphorylation sites, weakening ATP-binding pocket rigidity, and disrupting Mg2+ coordination.

Could this research help with sleep disorders?▼

Yes, understanding the molecular mechanism of the cyanobacterial circadian clock may provide new intervention strategies for circadian rhythm disorders such as sleep disorders and metabolic syndrome.

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References

  1. 1.Guo W, Zhao Y, Ke X, Feng H, Li A, Yan Y, Zhao Y. "Regulation mechanism study of residues E318/319 for KaiC protein phosphorylation.." Biophysical journal, 2026. PMID: 42324775 DOI: 10.1016/j.bpj.2026.06.023
Disclaimer: This content is for educational purposes only and is not medical advice. Evidence scores reflect the quality and quantity of available research, not clinical recommendations. Always consult a healthcare professional before starting any supplement or intervention.