1r8j

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Crystal Structure of Circadian Clock Protein KaiA from Synechococcus elongatus

Structural highlights

1r8j is a 2 chain structure with sequence from Synechococcus elongatus PCC 7942 = FACHB-805. The January 2008 RCSB PDB Molecule of the Month feature on Circadian Clock Proteins by David S. Goodsell is 10.2210/rcsb_pdb/mom_2008_1. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:X-ray diffraction, Resolution 2.03Å
Resources:FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

KAIA_SYNE7 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.[1] [2] [3] [4]

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

The circadian clock found in Synechococcus elongatus, the most ancient circadian clock, is regulated by the interaction of three proteins, KaiA, KaiB, and KaiC. While the precise function of these proteins remains unclear, KaiA has been shown to be a positive regulator of the expression of KaiB and KaiC. The 2.0-A structure of KaiA of S. elongatus reported here shows that the protein is composed of two independently folded domains connected by a linker. The NH(2)-terminal pseudo-receiver domain has a similar fold with that of bacterial response regulators, whereas the COOH-terminal four-helix bundle domain is novel and forms the interface of the 2-fold-related homodimer. The COOH-terminal four-helix bundle domain has been shown to contain the KaiC binding site. The structure suggests that the KaiB binding site is covered in the dimer interface of the KaiA "closed" conformation, observed in the crystal structure, which suggests an allosteric regulation mechanism.

Crystal structure of circadian clock protein KaiA from Synechococcus elongatus.,Ye S, Vakonakis I, Ioerger TR, LiWang AC, Sacchettini JC J Biol Chem. 2004 May 7;279(19):20511-8. Epub 2004 Mar 8. PMID:15007067[5]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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Citations
12 reviews cite this structure
The cyanobacterial circadian system: from biophysics to bioevolution.
Johnson et al. (2011)
11 more
43 other articles
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See Also

References

  1. ↑ Iwasaki H, Nishiwaki T, Kitayama Y, Nakajima M, Kondo T. KaiA-stimulated KaiC phosphorylation in circadian timing loops in cyanobacteria. Proc Natl Acad Sci U S A. 2002 Nov 26;99(24):15788-93. Epub 2002 Oct 21. PMID:12391300 doi:http://dx.doi.org/10.1073/pnas.222467299
  2. ↑ Xu Y, Mori T, Johnson CH. Cyanobacterial circadian clockwork: roles of KaiA, KaiB and the kaiBC promoter in regulating KaiC. EMBO J. 2003 May 1;22(9):2117-26. PMID:12727878 doi:10.1093/emboj/cdg168
  3. ↑ Kitayama Y, Iwasaki H, Nishiwaki T, Kondo T. KaiB functions as an attenuator of KaiC phosphorylation in the cyanobacterial circadian clock system. EMBO J. 2003 May 1;22(9):2127-34. PMID:12727879 doi:10.1093/emboj/cdg212
  4. ↑ Ishiura M, Kutsuna S, Aoki S, Iwasaki H, Andersson CR, Tanabe A, Golden SS, Johnson CH, Kondo T. Expression of a gene cluster kaiABC as a circadian feedback process in cyanobacteria. Science. 1998 Sep 4;281(5382):1519-23. PMID:9727980
  5. ↑ Ye S, Vakonakis I, Ioerger TR, LiWang AC, Sacchettini JC. Crystal structure of circadian clock protein KaiA from Synechococcus elongatus. J Biol Chem. 2004 May 7;279(19):20511-8. Epub 2004 Mar 8. PMID:15007067 doi:10.1074/jbc.M400077200

Contents


PDB ID 1r8j

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