Structural highlights
Function
[KAIA_THEEB] Component of the KaiABC clock protein complex, which constitutes the main circadian regulator in cyanobacteria. The KaiABC complex may act as a promoter-nonspecific transcription regulator that represses transcription, possibly by acting on the state of chromosome compaction. In the complex, it enhances the phosphorylation status of KaiC. In contrast, the presence of KaiB in the complex decreases the phosphorylation status of KaiC, suggesting that KaiB acts by antagonizing the interaction between KaiA and KaiC. A KaiA dimer is sufficient to enhance KaiC hexamer phosphorylation.
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
KaiA, KaiB and KaiC constitute the circadian clock machinery in cyanobacteria, and KaiA activates kaiBC expression whereas KaiC represses it. Here we show that KaiA is composed of three functional domains, the N-terminal amplitude-amplifier domain, the central period-adjuster domain and the C-terminal clock-oscillator domain. The C-terminal domain is responsible for dimer formation, binding to KaiC, enhancing KaiC phosphorylation and generating the circadian oscillations. The X-ray crystal structure at a resolution of 1.8 A of the C-terminal clock-oscillator domain of KaiA from the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1 shows that residue His270, located at the center of a KaiA dimer concavity, is essential to KaiA function. KaiA binding to KaiC probably occurs via the concave surface. On the basis of the structure, we predict the structural roles of the residues that affect circadian oscillations.
Crystal structure of the C-terminal clock-oscillator domain of the cyanobacterial KaiA protein.,Uzumaki T, Fujita M, Nakatsu T, Hayashi F, Shibata H, Itoh N, Kato H, Ishiura M Nat Struct Mol Biol. 2004 Jul;11(7):623-31. Epub 2004 May 30. PMID:15170179[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Uzumaki T, Fujita M, Nakatsu T, Hayashi F, Shibata H, Itoh N, Kato H, Ishiura M. Crystal structure of the C-terminal clock-oscillator domain of the cyanobacterial KaiA protein. Nat Struct Mol Biol. 2004 Jul;11(7):623-31. Epub 2004 May 30. PMID:15170179 doi:10.1038/nsmb781
