5c5e

Structure of KaiA dimer in complex with C-terminal KaiC peptide at 2.8 A resolutionStructure of KaiA dimer in complex with C-terminal KaiC peptide at 2.8 A resolution

Structural highlights

5c5e is a 4 chain structure with sequence from Synechococcus elongatus PCC 7942 = FACHB-805 and Synthetic construct. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:	X-ray diffraction, Resolution 2.82Å
Ligands:
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]

Publication Abstract from PubMed

In the cyanobacterial circadian clock, the KaiA, -B, and -C proteins with ATP constitute a post-translational oscillator. KaiA stimulates the KaiC autokinase, and KaiB antagonizes KaiA action. KaiA contacts the intrinsically disordered C-terminal regions of KaiC hexamer to promote phosphorylation across subunit interfaces. The crystal structure of KaiA dimer from Synechococcus elongatus with two KaiC C-terminal 20mer peptides bound reveals that the latter adopt an alpha-helical conformation and contact KaiA alpha-helical bundles via mostly hydrophobic interactions. This complex and the crystal structure of KaiC hexamer with truncated C-terminal tails can be fit into the electron microscopy (EM) density of the KaiA:KaiC complex. The hybrid model helps rationalize clock phenotypes of KaiA and KaiC mutants.

Protein-Protein Interactions in the Cyanobacterial Circadian Clock: Structure of KaiA Dimer in Complex with C-Terminal KaiC Peptides at 2.8 A Resolution.,Pattanayek R, Egli M Biochemistry. 2015 Aug 4;54(30):4575-8. doi: 10.1021/acs.biochem.5b00694. Epub, 2015 Jul 24. PMID:26200123^[5]

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

References

↑ 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
↑ 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
↑ 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
↑ 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
↑ Pattanayek R, Egli M. Protein-Protein Interactions in the Cyanobacterial Circadian Clock: Structure of KaiA Dimer in Complex with C-Terminal KaiC Peptides at 2.8 A Resolution. Biochemistry. 2015 Aug 4;54(30):4575-8. doi: 10.1021/acs.biochem.5b00694. Epub, 2015 Jul 24. PMID:26200123 doi:http://dx.doi.org/10.1021/acs.biochem.5b00694

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OCA

[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] Pattanayek R, Egli M. Protein-Protein Interactions in the Cyanobacterial Circadian Clock: Structure of KaiA Dimer in Complex with C-Terminal KaiC Peptides at 2.8 A Resolution. Biochemistry. 2015 Aug 4;54(30):4575-8. doi: 10.1021/acs.biochem.5b00694. Epub, 2015 Jul 24. PMID:26200123 doi:http://dx.doi.org/10.1021/acs.biochem.5b00694

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