Neurospora casein kinase 1a recruits the circadian clock protein FRQvia the C‐terminal lobe of its kinase domain

Two regions in casein kinase 1a (CK1a) are required for anchoring to frequency (FRQ), with approximately 100 sites targeted for hyperphosphorylation.

• The circadian clock timing in Neurospora relies on the hyperphosphorylation of FRQ, facilitated by CK1a anchoring.
• Mutation of the p1 region in CK1a leads to a non-functional circadian clock, while mutation of the p2 region results in non-viability.
• Both p1 and p2 are suggested to create an interface for the interaction between CK1a and FRQ.
• The anchoring mechanism allows CK1a's active site to remain accessible for phosphorylation at multiple sites on FRQ.

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