7s67 | pdb_00007s67
Extended conformation of daytime state KaiC
Structural highlights
Function[KAIC_SYNE7] Core component of the KaiABC clock protein complex, which constitutes the main circadian regulator in cyanobacteria. Binds to DNA. The KaiABC complex may act as a promoter-nonspecific transcription regulator that represses transcription, possibly by acting on the state of chromosome compaction.[1] [2] Publication Abstract from PubMedThe AAA(+) family member KaiC is the central pacemaker for circadian rhythms in the cyanobacterium Synechococcus elongatus. Composed of two hexameric rings of adenosine triphosphatase (ATPase) domains with tightly coupled activities, KaiC undergoes a cycle of autophosphorylation and autodephosphorylation on its C-terminal (CII) domain that restricts binding of clock proteins on its N-terminal (CI) domain to the evening. Here, we use cryogenic-electron microscopy to investigate how daytime and nighttime states of CII regulate KaiB binding on CI. We find that the CII hexamer is destabilized during the day but takes on a rigidified C2-symmetric state at night, concomitant with ring-ring compression. Residues at the CI-CII interface are required for phospho-dependent KaiB association, coupling ATPase activity on CI to cooperative KaiB recruitment. Together, these studies clarify a key step in the regulation of cyanobacterial circadian rhythms by KaiC phosphorylation. Coupling of distant ATPase domains in the circadian clock protein KaiC.,Swan JA, Sandate CR, Chavan AG, Freeberg AM, Etwaru D, Ernst DC, Palacios JG, Golden SS, LiWang A, Lander GC, Partch CL Nat Struct Mol Biol. 2022 Jul 21. pii: 10.1038/s41594-022-00803-w. doi:, 10.1038/s41594-022-00803-w. PMID:35864165[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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